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Full Program with Abstracts.


8:30 AM — Overview of Observations    [Chair: Fred Rasio]

Organizers: Welcome - Intro [10 mins]

Michel Mayor (Geneva):   Doppler Spectroscopy: A Path to the Detection of Earth-twins Hosted by Nearby Solar-type Stars

Space missions are the most succesful to detect rocky planets . Nevertheless if we want to detect very low mass planets hosted by nearby ( < 30 pcs ) solar-type stars, the Doppler spectroscopy remains the most promising technique. However due to the intrinsic variability of stellar atmospheres, it is challenging with that technique to detect Earth-twins in the habitable zone. Thanks to the angular separation between these planets and their host star as well as their luminosity these planetary systems will be the most important targets for future studies.

Josh Winn (MIT):   Architectures of Exoplanetary Systems

The basic geometry of the Solar System -- the shapes, spacings, and orientations of the planetary orbits -- has long been a subject of fascination, and inspiration for planet formation theories. For exoplanetary systems, those same properties have only recently come into focus. I will review our current knowledge about orbital distances and eccentricities, orbital spacings and mutual inclinations in multiplanet systems, the orientation of the host star's rotation axis, and the properties of planets in binary-star systems. I will also discuss the near-term prospects for learning more.

Natalie Batalha (NASA Ames):   Kepler & K2: One Spacecraft, Two Missions

This year, we mark twenty years of exploring the diversity of planets and planetary systems orbiting main sequence stars. Exoplanet discoveries spill into the thousands, and the sensitivity boundaries continue to expand. NASA's Kepler Mission unveiled a galaxy replete with small planets and revealed populations that don't exist in our own solar system. The mission has yielded a sample sufficient for computing planet occurrence rates as a function of size, orbital period, and host star properties. We've learned that every late-type star has at least one planet on average, that terrestrial-sized planets are more common than larger planets within 1 AU, and that the nearest, potentially habitable earth-sized planet is likely within 5pc. After four years of continuous observations, the Kepler prime mission ended in May 2013 with the loss of a second reaction wheel. Thanks to innovative engineering, the spacecraft gained a second lease on life and emerged as the ecliptic surveyor, K2. In many regards, K2 is a distinctly new mission, not only by pointing at new areas of the sky but also by focusing on community-driven goals that diversify the science yield. For exoplanets, this means targeting bright and low mass stars -- the populations harboring planets amenable to dynamical and atmospheric characterization. To date, the mission has executed 7 observing campaigns lasting ~80 days each and has achieved a 6-hour photometric precision of 30 ppm. A couple dozen planets have been confirmed, including two nearby (< 50 pc) systems on the watch-list for future JWST campaigns. While Kepler prime is setting the stage for the direct imaging missions of the future, K2 is easing us into an era of atmospheric characterization -- one spacecraft, two missions, and a bright future for exoplanet science.
Contributing Teams: Kepler/K2 Teams

Anne-Marie Lagrange (IPAG):   Direct Imaging and Distant Planets: a Path Towards a Full View of Planet Populations

Most of exo-planets have been found so far by indirect techniques, at separations typically less than 5 AU. Direct imaging offers the possibility to detect and study longer period planets. The few planets found so far, all giants, bring new challenges to the theories of planet formation and evolution. I will review the challenges associated to direct imaging, and the results obtained until today on these distant planets. I will stress on the opportunities offered by the new, extreme AO-fed, high contrasts imagers such as SPHERE and GPI and show the first results obtained with these instruments. I will also show how coupling imaging and indirect techniques can now help, for the first time, to investigate the population of giant planets, from a fraction up to hundreds of AU of some stars, giving the opportunity to estimate more accurately the frequency of giant planets around stars. I will finally propose a reasonable, longer term roadmap towards telluric planet imaging with the ELTs.

10 AM — Coffee Break

10:30 AM — Radial Velocities    [Chair: Michel Mayor]

David Charbonneau (Harvard):   Constraints on the Compositions of Small Planets from the HARPS-N Consortium

HARPS-N is an ultra-stable fiber-fed high-resolution spectrograph optimized for the measurement of very precise radial velocities. The NASA Kepler Mission has demonstrated that planets with radii between 1 - 2.5 that of the Earth are common around Sun-like stars. A chief objective of the HARPS-N Consortium is to measure accurately the masses and infer compositions for a sample of these small worlds. Here I report on our conclusions from the first three years. After analyzing the Kepler light curves to vet potential targets, favoring those with asteroseismic estimates of the stellar properties and excluding those likely to show high RV jitter, we lavished attention on our sample: We typically gathered 100 observations per target, which permitted a mass accuracy of better than 20%. We find that all planets smaller than 1.5 Earth radii are rocky, while we have yet to find a rocky planet larger than this size. I report on the resulting constraints on the planetary compositions, including previously unpublished estimates for several worlds. Comparison of the inferred iron-to-rock ratios to the spectroscopically determined abundances of Fe, Mg, and Si in the stellar atmospheres should provide insight into the formation of terrestrial worlds. I address the transition from rocky planets to Neptune-like worlds, noting that our targets are highly irradiated and hence have likely experienced atmospheric mass loss. The K2 and TESS Missions will provide a list of similarly sized planets around much brighter stars, for which the greater apparent brightness will permit us to measure densities of planets at longer orbital periods, where atmospheric escape will be less important.
Contributing Teams: The HARPS-N Consortium

Lauren Weiss (UC Berkeley):   Revised Masses and Densities of the Planets around Kepler-10

Determining which small exoplanets have stony-iron compositions is necessary for quantifying the occurrence of such planets and for understanding the physics of planet formation. Kepler-10 hosts the stony-iron world Kepler-10b, and also contains what has been reported to be the largest solid silicate-ice planet, Kepler-10c. Using 220 radial velocities (RVs), including 72 new precise RVs from Keck-HIRES, and 17 quarters of Kepler photometry, we obtain the most complete picture of the Kepler-10 system to date. We find that Kepler-10b (Rp = 1.47 R⊕) has mass 3.70 ± 0.43 M⊕ and density 6.44 ± 0.73 g cm−3. Modeling the interior of Kepler-10b as an iron core overlaid with a silicate mantle, we find that the core constitutes 0.17 ± 0.11 of the planet mass. For Kepler-10c (Rp = 2.35 R⊕) we measure mass 13.32 ± 1.65 M⊕and density 5.67 ± 0.70 g cm−3, significantly lower than the mass in Dumusque et al. (2014, 17.2±1.9 M⊕). Kepler-10c is not sufficiently dense to have a pure stony-iron composition. Internal compositional modeling reveals that at least 10% of the radius of Kepler-10c is a volatile envelope composed of either hydrogen-helium (0.0027 ± 0.0015 of the mass, 0.172±0.037 of the radius) or super-ionic water (0.309±0.11 of the mass, 0.305±0.075 of the radius). Transit timing variations (TTVs) of Kepler-10c indicate the likely presence of a third planet in the system, KOI-72.X. The TTVs and RVs are consistent with KOI-72.X having an orbital period of 24, 71, 82, or 101 days, and a mass from 1-7 M⊕.

Jennifer Burt (UC Santa Cruz):   The Automated Planet Finder's Detection of a 6-planet System Orbiting the Bright, Nearby Star HD219134

The Automated Planet Finder (APF) is the newest facility at Lick Observatory, comprised of a 2.4m telescope coupled with the high-resolution Levy echelle spectrograph. Purpose built for exoplanet detection and characterization, 80% of the telescope's observing time is dedicated to these science goals. The APF has demonstrated 1 m/s radial velocity precision on bright, RV standard stars and performs with the same speed-on-sky as Keck/HIRES when observing M-dwarfs. The APF has contributed to the detection of four planetary systems in its first two years of scientific operations. Our most recent detection is that of a 6-planet system around the bright (V=5.5), nearby (d=6.5pc), K3V star HD219134. The planets in this system have masses ranging from 3.5 to108 MEarth, with orbital periods from 3 to 2247 days. An independent detection of the inner 4 planets in this system by the HARPS-N team has shown that the 3d planet transits the star, making this system ideal for follow-up observations. I will discuss the APF's detections to date, highlighting HD219134, as well as the overall performance results of the telescope and our future observing strategy.

Howard Isaacson (UC Berkeley):   Refining Mass Measurements of Kepler Planets with Keck/HIRES

We present improved radial velocity mass measurements from Keck/HIRES for exoplanets detected by NASA’s Kepler Mission. Since Kepler’s launch 6 years ago, ~30 planetary systems have been monitored with radial velocities, resulting in measured masses for many planets between 1.0 and 4.0 Earth radii. The resulting planet masses have been used to determine the transition between planets with a rocky interior and those with a lower density interior which requiring significant H/He atmospheres. We provide updated masses and densities for those planets published in Marcy et al (2014) based on two additional observing seasons with HIRES of the Kepler field. These radial velocities also reveal non-transiting planets in systems with previously found transiting planets. One such system has a non-transiting planet with a period between two transiting planets, providing a constraint on the co-planarity of the system. Finally, we provide an updated mass-radius relation, showing the distinction between planets that must have a substantial iron-silicate interior, and those requiring significant contributions from volatiles such as hydrogen and helium.

Megan Bedell (U Chicago):   A Super-Earth around a Solar Twin with Evidence for Planet Accretion

Over the last four years we have been carrying out a HARPS radial velocity planet search program aimed at solar twins. Solar twins are a class of stars uniquely suited for high-precision chemical abundance measurements, and the goal of this project is to search for correlations between stellar abundances and planet frequency at a level of sensitivity only solar twins can provide. We recently discovered a 3 Earth mass planet on a 1.8 day orbital period around one of our targets. Our spectroscopic analysis of the host star indicates that it may have accreted planetary material: its chemical abundance pattern has an enhancement in refractory materials and the stellar rotation rate is unusually high for its age, possibly a marker of spin-up. This raises the intriguing possibility that the super-Earth is the core remnant of an accreted hot Jupiter. We present this system as a case study of the power of high-precision host star characterization.
Contributing Teams: Solar Twin Planet Search Team

Marion Neveu Van Malle (Geneva):   Hot Jupiters with Companions: Results of the Long-term CORALIE Survey

For twenty years hot Jupiters have been challenging planet formation theories. While in-situ formation has rapidly been rejected, the giant planets migration mechanisms are still not well understood. Disc migration is probably the dominant scenario but it cannot explain the observed population of hot Jupiters. Dynamical models involving the influence of an additional planetary or stellar companion through scattering or Kozai-Lidov mechanisms could also explain planetary migration. Their role needs to be characterised. High eccentricity migration mechanisms are triggered by the presence of an additional object. Knutson et al. (2014) searched for planetary companions to hot Jupiters and deduced that half of them had a giant planetary companion. We have performed our own independent search for companions of hot Jupiters. Since 2007, we have monitored the Southern WASP confirmed planets with the high-resolution echelle spectrograph CORALIE. Our sample includes more than 100 targets, including 90 that have been followed for more than three years. Our results slightly differ from those of Knutson et al. (2014). I will present the results of this survey regarding the statistics of companions of hot Jupiters. I will compare our detections with the planetary occurrence rates as well as with the binary stars occurrence rates. I will describe the correlations between the presence of a companion and the properties of the hot Jupiter.

Marta Bryan (Caltech):   Statistics of Long-Period Gas Giant Planets in Known Planetary Systems

We conducted a Doppler survey at Keck combined with NIRC2 K-band AO imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter mass planets out to 20 AU for a majority of the stars in our sample, and we report the discovery of eight new long-period planets in addition to 20 RV trends at 3 sigma significance indicating the presence of an outer companion beyond 5 AU. We combined our RV observations with AO imaging to determine the range of allowed masses and orbital separations for these companions and fit this population with a power law in mass and semi-major axis. We estimate the total occurrence rate of companions in our sample, and find that hot and warm gas giants inside 1 AU are more likely to have an outer companion than cold gas giants. We also find that planets with an outer companion have higher than average eccentricities than their single counterparts, suggesting that dynamical interactions between planets may play an important role in these systems.

Lunch Break

2:00 PM — Transiting Planets I    [Chair: Didier Queloz]

Zach Berta-Thompson (MIT):   A Rocky Planet Transiting a Nearby Low-Mass Star

Results from Kepler indicate that M dwarfs host, on average, at least 1.4 planets between 0.5 and 1.5 Earth radii per star. Yet, the closest small planets known to transit M dwarfs have been too distant to allow Doppler measurements of their masses or spectroscopic studies of their atmospheres. Here, we announce a new planet discovered by the MEarth-South observatory, an Earth-size planet transiting an M dwarf that is only 12 pc away. The density of the planet, determined from radial velocity observations with HARPS, is consistent with an Earth-like rock/iron composition. With an equilibrium temperature of 530K (assuming a Bond albedo of 0.3), this planet is cooler than most other rocky planets with measured densities. Although too hot to be habitable, it is cool enough that it may have retained a substantial atmosphere over its lifetime. Thanks to the star's proximity and its diminutive size of only 1/5th the radius of the Sun, this new world likely provides the first opportunity for our community to spectroscopically examine the atmosphere of a terrestrial exoplanet. We estimate that JWST could secure high signal-to-noise spectra of the planet's atmosphere, both in transmission during transit and in emission at secondary eclipse.

Eric Ford (Penn State):   Securing the Extremely Low-Densities of Low-Mass Planets Characterized by Transit Timing Variations

Transit timing variations (TTVs) provide an excellent tool to characterize the masses and orbits of dozens of small planets, including many at orbital periods beyond the reach of both Doppler surveys and photoevaporation-induced atmospheric loss. Dynamical modeling of these systems has identified low-mass planets with surprisingly large radii and low densities (e.g., Kepler-79d, Jontof-Hutter et al. 2014; Kepler-51, Masuda 2014; Kepler-87c, Ofir et al. 2014). Additional low-density, low-mass planets will likely become public before ExSS III (Jontof-Hutter et al. in prep). Collectively, these results suggest that very low density planets with masses of 2-6 MEarth are not uncommon in compact multiple planet systems. Some astronomers have questioned whether there could be an alternative interpretation of the TTV observations. Indeed, extraordinary claims require extraordinary evidence. While the physics of TTVs is rock solid, the statistical analysis of Kepler observations can be challenging, due to the complex interactions between model parameters and high-dimensional parameter spaces that must be explored. We summarize recent advances in computational statistics that enable robust characterization of planetary systems using TTVs. We present updated analyses of a few particularly interesting systems and discuss the implications for the robustness of extremely low densities for low-mass planets. Such planets pose an interesting challenge for planet formation theory and are motivating detailed theoretical studies (e.g., Lee & Chiang 2015 and associated ExSS III abstracts).

Phil Muirhead (Boston U):   The Occurrence of Compact Multiples Orbiting Mid-M Dwarf Stars

Various investigations of exoplanet occurrence indicate that short-period planets are common around M dwarf stars. However, not all M dwarfs are equal, with mid-to-late type M dwarfs being significantly smaller, fully convective, and showing different activity phenomena when compared to early-type M dwarf stars. Accurate exoplanet statistics for mid-to-late M dwarfs is much more challenging owing to the few systems surveyed with adequate precision to detect small planets. Using data from NASA’s Kepler Mission, we confirmed and characterized two new exoplanetary systems orbiting mid-M dwarfs: Kepler-445 and Kepler-446. When combined with Kepler-42, and isolating all mid-M dwarf stars observed by Kepler with the precision necessary to detect similar systems, we calculate that one-fifth of mid-M dwarf stars host compact multiples (multiple planets with periods of less than 10 days) for a wide range of metallicities. We suggest that the inferred planet masses for these systems support highly efficient accretion of protoplanetary disk metals by protoplanets orbiting low-mass stars.
Contributing Teams: Philip S. Muirhead, Andrew W. Mann, Andrew Vanderburg, Timothy D. Morton, Adam Kraus, Michael Ireland, Jonathan J. Swift, Gregory A. Feiden, Eric Gaidos, J. Zachary Gazak

Fred Adams (Michigan):   The Dynamics of the WASP-47 Planetary System: A Hot Jupiter, Two Additional Planets, and Observable TTVs

New data from the K2 mission indicate that WASP-47, a previously known Hot Jupiter host, also hosts two additional transiting planets: a Neptune-sized outer planet and a super-Earth inner companion. The measured period ratios and size ratios for these planets are unusual (extreme) for Hot Jupiter systems. We measure the planetary properties from the K2 light curve and detect transit timing variations, thereby confirming the planetary nature of the outer planet. We performed a large ensemble of numerical simulations to study the dynamical stability of the system and to find the theoretically expected transit timing variations (TTVs). The system is stable provided that the orbital eccentricities are small. The theoretically predicted TTVs are in good agreement with those observed, and we use the TTVs to determine the masses of two planets, and place a limit on the third. The WASP-47 planetary system is important because the companion planets can both be inferred by TTVs and are also detected directly through transit observations. The depth of the Hot Jupiter’s transits make ground-based TTV measurements possible, and the brightness of the host star makes it amenable for precise radial velocity measurements. The system thus serves as a Rosetta Stone for understanding TTVs as a planet detection technique. Moreover, this compact set of planets in nearly circular, coplanar orbits demonstrates that at least a subset of Jupiter-size planets can migrate in close to their host star in a dynamically quiet manner. As final curiosity, WASP-47 hosts one of few extrasolar planetary systems that can observe Earth in transit.

Kat Deck (Caltech):   Analytic Formulae for Transit Timing Variations of Planets

Gravitational interactions between planets in transiting exoplanetary systems lead to variations in the times of transit (TTVs) that are diagnostic of the planetary masses and the dynamical state of the system. I will present analytic formulae for TTVs which can be applied to planetary systems with nearly circular orbits which are not caught in a mean motion resonance. The formulae relate physical parameters, like masses and orbital elements, to direct TTV observables, including shape, amplitude, and timescales. Importantly, the formulae highlight which components of TTVs break degeneracies to allow for unique measurements of planet masses and eccentricities. Additionally, modeling of TTV data using our analytic formulae can be nearly 4 orders of magnitude faster compared with n-body integration. For a number of Kepler systems with TTVs, I will show that our formulae lead to accurate mass and orbital element measurements without full dynamical analyses involving direct integration of the equations of motion. The analytic formulae may ultimately allow for a homogenous analysis of the TTVs (or lack thereof) of many multi-planet systems.

Sam Hadden (Northwestern):   Kepler Planet Masses and Eccentricities from TTVs: Analytic and N-body Results

Several Kepler planets reside in multi-planet systems where gravitational interactions result in transit timing variations (TTVs) that provide exquisitely sensitive probes of their masses of and orbits. Measuring these planets' masses and orbits constrains their bulk compositions and can provide clues about their formation. However, inverting TTV measurements in order to infer planet properties can be challenging: it involves fitting a nonlinear model with a large number of parameters to noisy data, often with significant degeneracies between parameters. I present results from two complementary approaches to TTV inversion: Markov chain Monte Carlo simulations that use N-body integrations to compute transit times and a simplified analytic model for computing the TTVs of planets near mean motion resonances. The analytic model allows for straightforward interpretations of N-body results and provides an independent estimate of parameter uncertainties that can be compared to MCMC results which may be sensitive to factors such as priors. We have conducted extensive MCMC simulations along with analytic fits to model the TTVs of dozens of Kepler multi-planet systems. We find that the bulk of these sub-Jovian planets have low densities that necessitate significant gaseous envelopes. We also find that the planets' eccentricities are generally small but often definitively non-zero.

3:30 PM — Coffee Break

4:00 PM — Transiting Planets II    [Chair: Natalie Batalha]

Ian Crossfield (U Arizona):   Latest Results From the K2 M Dwarf Program

Small stars and small planets are ubiquitous in the Galaxy. Planets smaller than ~2.5 Earth radii occur more frequently than any other type of planet; stars with masses below ~0.4 Solar masses are the most common type of star. Nonetheless we know much less about the formation, evolution, interior composition, atmospheric makeup, and population trends of M dwarf planetary systems than we do for planets orbiting Sunlike stars. Our team has made major progress in identifying and validating new planet candidates discovered by NASA's K2 mission, especially including many planets orbiting M dwarfs. I will review our discoveries and their system architectures in the first five K2 fields, and describe how we are already finding many excellent candidates for ongoing & future followup studies with RV spectrographs (to measure planetary masses) and HST, Spitzer, and/or JWST (to measure atmospheric composition).

Evan Sinukoff (U Hawaii):   Discovery and Characterization of Small Planets from K2

In 2014, the Kepler Telescope was repurposed for a new "K2" mission, searching for transiting planets in ~14 fields along the ecliptic, for 80 days each. We are conducting a follow-up program to detect and characterize K2 planets to better understand small planet diversity. I present the detection and confirmation of over 150 transiting planets, mostly sub-Neptune-size, in the first five K2 fields. This includes more than a dozen multi-planet systems, many of which are bright enough for spectroscopic follow-up to measure planet masses via radial velocities (RVs). I report preliminary masses and densities of planets in a few of these new multi-planet systems, constrained by Keck HIRES RVs. Continued RV follow-up will probe the compositional diversity of small planets, examining the degree to which environmental factors (e.g. stellar properties, incident flux, system architectures) sculpt the planet mass-radius diagram.

Diana Dragomir (U Chicago):   Follow-up of K2 Planet Candidates with the LCOGT Network

K2 has proven to be an outstanding successor to the Kepler mission. It has already revealed dozens of new planet candidates, and unlike those found by the primary mission, many of these systems’ host stars are sufficiently bright to allow extensive follow-up observations. This is especially important since each of the K2 observing campaigns are only ~80 days long, leaving the community with the discovery of exciting new systems but often not enough time coverage to enable a thorough characterization of these systems. We are leading a large effort to observe K2 transiting planet candidates with the LCOGT telescope network. LCOGT’s longitudinal coverage, multiple identical telescopes per site and automated queue observing make it an ideal facility for fast, high-precision and multi-color follow-up. Our program focuses on specific aspects of K2 follow-up for which the network is especially powerful: period determination for candidates with fewer than three K2 transits; transit timing variation monitoring to measure planetary masses, orbital parameters and to search for additional planets in multiple systems; and multi-color photometry to vet planet candidates and carry out preliminary atmospheric spectroscopy. We will present new results for a selection of systems observed so far through this program. These include K2-19, a multi-planet system extremely close to 3:2 resonance and experiencing transit timing variations with amplitudes as large as one hour; EPIC201702477, a long-period planet with only two K2 transits; WASP-47, a system hosting a hot Jupiter and two K2-discovered small planets; and EPIC201637175b, a disintegrating rocky planet. Our program demonstrates that LCOGT is uniquely positioned to be the primary ground-based photometric follow-up resource for K2 exoplanet discoveries, but also for the numerous bright systems that will result from the TESS mission. LCOGT photometry complements ongoing radial velocity and atmospheric spectroscopy efforts to reveal a more complete picture of the bright, nearby exoplanet systems discovered by these missions.

Didier Queloz (Cambridge):   NGTS, a New Transit Search Facility in Operation in the Southern Sky

NGTS is an automated wide field transit survey designed and built to detect transiting Neptune size planet on bright K dwarfs stars. NGTS first light was obtained in summer 2015. First preliminary results as well as details simulations of the survey expectation will be presented during this talk. Bright K dwarfs stars are targets of special interest to look for transiting planets and gather information about planetary structure and the nature of atmospheric composition of exoplanets. Planetary transit to be detected by NGTS will provide us with a unique target sample for further characterization by HARPS, VLT, and later JWST. Interesting synergies with TESS may be found as well on the coolest stars of the sample (M stars).
Contributing Teams: Didier Queloz & Chris Watson, Heather Cegla, Pete Wheatley, Don Pollacco, Richard West, James McCormac, Tom Marsh, Boris Gaensicke, Danny Steeghs, Simon Walker, Tom Louden, Hugh Osborne, David Armstrong, Amanda Doyle, Francesca Faedi, Mike Goad, Matt Burleigh, Sarah Casewell, Nigel Bannister, Andy Grange, Alex Chaushev, Stephane Udry, Bruno Chazelas, Ludovic Genolet, Marion Neveu, Daniel Bayliss, Claudia Dreyer, Amaury Triaud, Heike Rauer, Anders Erikson, Philipp Eigmueller, Juan Cabrera, Szilard Csizmadia Simon Hodgkin, Aimee Hall, Brice Demory, Gregory Lambert, Maximilian Guenther, James Jenkins

Sean Mills (U Chicago):   Kepler-223: A Resonant Chain of Four Sub-Neptune Planets

The Kepler mission has revealed an abundance of pairs of planets in the same system which often lie near, but not exactly on, resonance. Understanding how and when they entered a resonance and were removed from it has implications for their birthplaces and planetary structure. Here we characterize Kepler-223 (KOI-730), an outstanding example of a system of small planets in resonance. We perform TTV, photodynamic, stability, and migration analyses to determine the system's most likely current parameters and resonant state. Its four sub-Neptune planets form a chain linked by 4:3, 3:2, and 2:1 resonances that cause measurable dynamical effects and imply a disk-migration origin. Tidal dissipation in the planets or wide-scale instability may eventually transform resonant chains of planets like Kepler-223 into the more common type of architecture.

Darin Ragozzine (FIT):   Kepler-80 and the Frequency of STIPs

At ESS-II, Kepler and detailed radial velocity surveys had confirmed that systems of multiple, small, close-in planets were relatively common, but there was a order of magnitude difference between the estimated frequency of STIPs from Kepler (~5%, Lissauer, Ragozzine et al. 2011) and the frequency from RV surveys (~50%, Mayor et al. 2011). Continued Kepler observations are providing insight into the properties of this new population, now called STIPs (Systems with Tightly-packed Inner Planets), both through individually interesting systems and through a large ~homogeneous population. Kepler-80 (KOI-500) is an important system due to its still-unique extreme three-body resonance configuration and its relatively compact configuration. I will present a full dynamical TTV analysis of this system including densities for the four outer planets. We will also discuss the statistical evidence for whether Kepler-80 and similar extremely-tightly-packed systems could be considered a separate population from the STIPs. Radial Velocity surveys have not detected any of these extremely-tightly-packed systems (~4 planets with periods within a factor of ~3), so with the masses from our TTV analysis, we investigate the ability of radial velocity surveys to detect such systems. We find that it is extremely difficult in practice to correctly disentangle the signals for all five planets of Kepler-80 due to the low-SNR amplitudes and similar frequencies involved (even for circular orbits with no resonance effects). STIPs will, to some degree, inherit this propensity for RV measurements to miss planets with similar periods; this has potentially important effects on the completeness estimates for RV surveys of STIPs. We address current results and present a roadmap for investigating the frequency of such systems in more detail using the Planetary System Simulator (SysSim), an extension of the population analysis of Lissauer, Ragozzine, et al. 2011.


8:00 — 9:30 PM Evening Panel Discussion: Harassment in Astronomy    [Organizer: Christina Richey, AAS CSWA]


8:30 AM — Ultrashort Periods and Planet-Star Interactions    [Chair: Rosemary Mardling]

David Ehrenreich (Geneva):   A Giant Cloud of Hydrogen Escaping the Warm Neptune-mass Planet GJ 436b

Exoplanets in extreme irradiation environments, close to their parent stars, could lose some fraction of their atmospheres because of the extreme irradiation. Atmospheric mass loss has been observed during the past 12 years for hot gas giants, as large (~10%) ultraviolet absorption signals during transits. Meanwhile, no confident detection have been obtained for lower-mass planets, which are most likely to be significantly affected by atmospheric escape. In fact, hot rocky planets observed by Corot and Kepler might have lost all of their atmosphere, having begun as Neptune-like. The signature of this loss could be observed in the ultraviolet, when the planet and its escaping atmosphere transit the star, giving rise to deeper and longer transit signatures than in the optical. I will report on new Hubble observations of the Neptune-mass exoplanet GJ 436b, around which an extended atmosphere has been tentatively detected in 2014. The new data reveal that GJ 436b has huge transit depths of 56.3±3.5% in the hydrogen Lyman-alpha line, far beyond the 0.69% optical transit depth, and even far beyond mass loss signatures observed at the same wavelength from more irradiated gas giants. We infer from this repeated observations that the planet is surrounded and trailed by a large exospheric cloud of hydrogen, shaped as a giant comet, much bigger than the star. We estimate a mass-loss rate, which today is far too small to deplete the atmosphere of a Neptune-like planet in the lifetime of the parent star, but would have been much greater in the past. This 16-sigma detection opens exciting perspectives for the atmospheric characterization of low-mass and moderately-irradiated exoplanets, a large number of which will be detected by forthcoming transit surveys.
Contributing Teams: Vincent Bourrier, Peter J. Wheatley, Alain Lecavelier des Etangs, Guillaume Hébrard, Stéphane Udry, Xavier Bonfils, Xavier Delfosse, Jean-Michel Désert, David K. Sing & Alfred Vidal-Madjar

Vincent Bourrier (Geneva):   Evaporating Atmospheres: from Hot Jupiters to Warm Neptunes

Atmospheric escape has first been detected through transit observations of massive hot Jupiters like HD209458b and HD189733b. Absorption signatures in the Lyman-alpha line of their host stars have been attributed to comet-like tails of escaping neutral hydrogen, blown away by the stellar radiation pressure or stellar wind interactions. The recent detection of a giant exosphere surrounding the warm Neptune GJ 436 b has shed new light on the evaporation of close-in planets, revealing that moderately irradiated, low-mass exoplanets could make exceptional targets for studying this mechanism and its impact on exoplanets. In this talk, I will show the role played by stellar radiation pressure on the structure of GJ436b exosphere and its transmission spectrum, highlighting its differences with the known evaporating hot Jupiters. Furthermore, while the three observations performed in the Lyman-α line of GJ 436 show repeatable transit variations, the spectra observed at each of epoch display specific features that require additional physics. I will present preliminary results as for the origin of this temporal variability.

Eric Lopez (Edinburgh):   Re-inflated Warm Jupiters around Red Giants: A New Test for Models of Hot Jupiter Inflation

Ever since the discovery of the first transiting hot Jupiter, models have sought to explain the anomalously large radii of highly irradiated gas giants. We now know that the size of the hot Jupiter radius anomaly scales strongly with a planet’s level of irradiation and numerous models have since been developed to help explain these inflated radii. In general however, these models can be grouped into two broad categories: 1) models that directly inflate planetary radii by depositing a fraction of the incident irradiation in the convective interior and 2) models that simply slow a planet’s radiative cooling allowing it to retain more heat from formation and thereby delay contraction. Here we propose a new test to distinguish between these two classes of models, by examining the post-main sequence radius evolution of gas giants with moderate orbital periods of ~10-30 days. If hot Jupiter inflation actively deposits heat in a planets interior then current and upcoming transit surveys should uncover a new population of “re-inflated” gas giants around post main sequence stars.

Francesca Valsecchi (Northwestern):   Evolution of Giant Planets close to the Roche Limit

Two formation models have been proposed to explain hot Jupiters’ tight orbits. These could have migrated inward in a disk (disk migration), or they could have formed via tidal circularization of an orbit made highly eccentric following gravitational interactions with a companion (high-eccentricity migration). I will show how current observations coupled with a detailed treatment of tides can be used to constrain both hot Jupiter formation and tidal dissipation theories. Eventually, stellar tides will cause the orbits of many hot Jupiters to decay down to their Roche limit. Using a detailed binary mass transfer model we show how a hot Jupiter undergoing a phase of Roche-lobe overflow (RLO) leads to lower-mass planets in orbits of a few days. The remnant planets have a rocky core and some amount of envelope material, which is slowly removed via photo-evaporation at nearly constant orbital period; these have properties resembling many of the observed super-Earths and sub-Neptunes. For these remnant planets we also predict an anti-correlation between mass and orbital period; very low-mass planets in ultra-short periods cannot be produced through this type of evolution.

Leslie Rogers (UC Berkeley):   Exo-Mercury Analogues and the Roche Limit for Close-Orbiting Rocky Planets

The origin of Mercury's enhanced iron content is a matter of ongoing debate. The characterization of rocky exoplanets promises to provide new independent insights on this topic, by constraining the occurrence rate and physical and orbital properties of iron-enhanced planets orbiting distant stars. The ultra-short-period transiting planet candidate KOI-1843.03 (0.6 Earth-radius, 4.245 hour orbital period, 0.46 Solar-mass host star) represents the first exo-Mercury planet candidate ever identified. For KOI-1843.03 to have avoided tidal disruption on such a short orbit, Rappaport et al. (2013) estimate that it must have a mean density of at least 7g/cc and be at least as iron rich as Mercury. This density lower-limit, however, relies upon interpolating the Roche limits of single-component polytrope models, which do not accurately capture the density profiles of >1000 km differentiated rocky bodies. A more exact calculation of the Roche limit for the case of rocky planets of arbitrary composition and central concentration is needed. We present 3D interior structure simulations of ultra-short-period tidally distorted rocky exoplanets, calculated using a modified version of Hachisu’s self-consistent field method and realistic equations of state for silicates and iron. We derive the Roche limits of rocky planets as a function of mass and composition, and refine the composition constraints on KOI-1843.03. We conclude by discussing the implications of our simulations for the eventual characterization of short-period transiting planets discovered by K2, TESS, CHEOPS and PLATO.

Smadar Naoz (UCLA):   Signatures for Dynamical Evolution of Short Period M-dwarf Planets

Recently, planetary systems containing sub-Neptune-sized planets with semimajor axes less than the Mercury--Sun separation have been discovered around a wide range of stars. We show that there are several significant differences between M- and G-dwarf close-in sub-Neptune planets. We find that a significant precent of close-in M-dwarf planets reside interior to the star’s estimated protoplanetary disk edge, unlike G-dwarf planets. Presumably these planets had to be brought in, after the disk was evaporated, by a dynamical mechanism. This should resulted in large eccentric planets, furthermore, those planets with extreme eccentricities may have circularized to a tight orbit. However, we also find that the eccentricity distribution of M-dwarf is significantly suppressed around the e~0 and for e>0.4 while the G-dwarfs eccentricity distribution covers the entire range. We suggest that tidal evolution, after a scattering event, in both stars plays an important role in shaping these distributions. Because M-dwarfs spands more time in pre-main sequence phase tides operate for longer timescales, which can contribute to damping the large eccentricities. However, tidal forces are proportional to the mass of the star, and as such they are less efficient for M-dwarf planet and do not result in circularization.
Contributing Teams: Bao-Minh Hoang, Gongjie Li, John Johnson

10 AM — Coffee Break

10:30 AM — Dynamical Evolution    [Chair: Eric Ford]

Natalia Storch (Caltech):   Spin-Orbit Coupling and the Production of Misaligned Hot Jupiters via Lidov-Kozai Oscillations

Many hot Jupiter systems exhibit misalignment between the orbital axis of the planet and the spin axis of its host star. While this misalignment could be primordial in nature, a large fraction of hot Jupiters are found in systems with distant stellar companions, and thus could have undergone Lidov-Kozai (LK) oscillations and acquired their misalignment dynamically. Here we present a study of the effect of spin-orbit coupling during LK oscillations, and the resulting spin-orbit misalignment angle distributions. We show that spin-orbit coupling induces complex, often chaotic, behavior in the spin axis of the host star, and that this behavior depends significantly on the mass of the planet and the properties of the host star (mass and spin history). We develop a semi-analytical framework that successfully explains most of the possible stellar spin behaviors. We then present a comprehensive population synthesis of hot Jupiters created via the LK mechanism, and discuss their possible observable signatures.

Gongjie Li (Harvard):   Are Tidal Effects Responsible for Exoplanetary Spin-Orbit Alignment?

Obliquities of planet-hosting stars may be clues about the formation of planetary systems. Previous observations led to the hypothesis that for close-in giant planets, spin-orbit alignment is enforced by tidal interactions. Here, we examine two potential problems with this hypothesis. First, Mazeh and coworkers recently used a new technique -- based on the amplitude of starspot-induced photometric variability -- to conclude that spin-orbit alignment is common even for relatively long-period planets, which would not be expected if tides were responsible. We re-examine the data and find a statistically significant correlation between photometric variability and planetary orbital period, which is at least qualitatively consistent with tidal interactions. Second, Rogers and Lin argued against a particular theory for tidal realignment by showing that initially retrograde systems would fail to be re-aligned, in contradiction with the observed prevalence of prograde systems. We present a simple model that overcomes this problem by taking into account the dissipation of inertial waves and the equilibrium tide, as well as magnetic braking. Thus, we find both problems to be less serious than they first appeared, although the tidal model still has shortcomings.

Jason Steffen (U Nevada):   Features in the Architectures of Exoplanet Systems

Data from NASA's Kepler mission allow for new and innovative studies of the distributions of planetary orbits and sizes. These distributions have important implications for our understanding of planet formation. I present the results of recent studies of the architectures of Kepler systems where a number of intruiguing features are manifest. Specifically, there is a notable lack of nearby companions to short-period planets and there is a significant excess of planet pairs with an orbital period ratio near 2.2. These features currently lack an explanation, yet may yield important insights into the late stages of planet formation and the subsequent dynamical evolution of the system. I also present results and anlysis of dynamical simulations of dynamical instability in closely-packed planetary systems. These simulations show an important invariance in the timescale to instability with respect to the orbital distance of the planets.

Sourav Chatterjee (Northwestern):   Planetesimal Scattering and its Implications for the Period-Ratio Distribution of Kepler Planet Pairs

Period ratios of most adjacent planet pairs in Kepler's multiplanet systems seem random. However, there is a clear excess and dearth of systems just exterior and interior to major mean motion resonances, respectively. We show that dynamical interactions between initially resonant planet pairs and planetesimals in a planetesimal disk can naturally produce the observed asymmetric abundances in period ratios of near-resonant pairs for a wide variety of planet and planetesimal disk properties (Chatterjee & Ford 2015). We further extend this study to include planet pairs initially not in resonance. We will present our key results from this large suite of simulations. We will also discuss implications of planetesimal scattering for the observable properties of these planets including their TTV signal and mass-radius properties as a result of planetesimal accretion.

Sarah Morrison (U Arizona):   Orbital Stability of Multi-Planet Systems: Behavior at High Masses

We explore the relationships between planet separation, mass, and stability timescale in high mass multi-planet systems containing planet masses and multiplicities relevant for planetary systems detectable via direct imaging. Extrapolating empirically derived relationships between planet mass, separation, and stability timescale derived from lower mass planetary systems misestimate the stability timescales for higher mass planetary systems by more than an order of magnitude at close separations near the two body Hill stability limit. We also find that characterizing critical separations in terms of period ratio produces a linear relationship between log-timescale and separation with the same slope for planet-star mass ratios comparable to or exceeding Jupiter’s, but this slope steepens for lower mass planetary systems. We discuss possible mechanisms for instability that result in this behavior including perturbing adjacent planet pairs into an overlap regime between 1st and sometimes 2nd order mean motion resonances.

Samantha Lawler (NRC-Herzberg):   Fomalhaut b is Probably Not a Planet: Frequent Collisions within the Fomalhaut Debris Disk

Fomalhaut hosts a beautiful debris disk ring and a directly imaged planet candidate, Fomalhaut b, which seems to continually defy expectations. Originally thought to be a Jovian-mass planet constraining the ring, its unexpected spectral properties and highly eccentric, possibly ring-crossing orbit have completely ruled out that possibility. Many theories have been proposed to explain the weird properties of Fomalhaut b, including a large circumplanetary ring, a system of irregular satellites, and a recent small body collision. We expand on the last theory, discussing our collisional probability simulations of the Fomalhaut debris disk, based on the structure of our Kuiper belt, which show the catastrophic disruption rate of d~100 km bodies in the high-eccentricity scattering component is several per decade. This model paints a picture of the Fomalhaut system as having recently (with ~10-100 Myr) experienced a dynamical instability within its planetary system, which scattered a massive number of planetesimals onto large, high-eccentricity orbits similar to that of Fom b. If Fomalhaut b is indeed a dust cloud produced by such a collision, we should soon see another appear, while Fomalhaut b will expand until it is either resolved or becomes too faint to be seen.

Lunch Break

2:00 PM — Direct Imaging I    [Chair: Anne-Marie Lagrange]

Jennifer Patience (ASU):   The Gemini Planet Imager Exoplanet Survey (GPIES) Campaign Initial Results

The Gemini Planet Imager (GPI) is a next-generation coronagraphic integral field unit with the sensitivity and resolution to detect planetary companions with separations of 0”.2 to 1”.0 around a large set of stars. An 890-hour GPI survey of 600 young, nearby stars commenced in late-2014, and approximately 100 stars have been observed thus far. The central aims of the program are: (1) the discovery of a population of giant planets with orbital radii of 5-50 AU comparable to Solar System gas giant orbits, (2) the characterization of the atmospheric properties of young planetary companions, and (3) the exploration of planet-disk interactions. Initial results from GPI exoplanet observations include the discovery of a new planetary companion to a young F-star; the planet spectrum shows a strong signature of methane absorption, indicating a cooler temperature than previously imaged young planets. An overview of the survey scope, current detection limits, and initial results will be presented.
Contributing Teams: The Gemini Planet Imager Exoplanet Survey Team (PI Macintosh)

Eric Nielsen (SETI Inst):   Astrometric Confirmation and Orbital Parameters of the Young Exoplanet 51 Eridani b with the GPI

The Gemini Planet Imager Exoplanet Survey discovered the young, 2 Jupiter mass planet 51 Eri b based on observations conducted in December 2014 and January 2015. It is the lowest mass extrasolar planet ever detected by direct imaging and shows strong methane absorption, and is at a projected separation of just 13 AU from its host star. We present new astrometry from late 2015 that confirms 51 Eri b is a bound planet and not an interloping brown dwarf. Orbital motion is detected despite monitoring the system for less than a year. We have implemented a computationally efficient Monte Carlo technique for fitting a range of possible orbital motion based on astrometry covering a small fraction of the period and producing distributions of orbital parameters consistent with the measurements. We apply this technique to the astrometry of 51 Eri b and present preliminary orbital parameter distributions of this intriguing planet.
Contributing Teams: The Gemini Planet Imager Exoplanet Survey (GPIES) Team

Mark Marley (NASA Ames):   Do Photochemical Hazes Cloud the Atmosphere of 51 Eri b?

The first young giant planet to be discovered by the Gemini Planet Imager was the ~ 2MJ planet 51 Eri b. This ~20 Myr old young Jupiter is the first directly imaged planet to show unmistakable methane in H band. To constrain the planet’s mass, atmospheric temperature, and composition, the GPI J and H band spectra as well as some limited photometric points were compared to the predictions of substellar atmosphere models. The best fitting models reported in the discovery paper (Macintosh et al. 2015) relied upon a combination of clear and cloudy atmospheric columns to reproduce the data. In the atmosphere of an object as cool as 700 K the global silicate and iron clouds would be expected to be found well below the photosphere, although strong vertical mixing in the low gravity atmosphere is a possibility. Instead, clouds of Na2S, as have been detected in brown dwarf atmospheres, are a likely source of particle opacity. As a third explanation we have explored whether atmospheric photochemistry, driven by the UV flux from the primary star, may yield hazes that also influence the observed spectrum of the planet. To explore this possibility we have modeled the atmospheric photochemistry of 51 Eri b using two state-of-the-art photochemical models, both capable of predicting yields of complex hydrocarbons under various atmospheric conditions. We also have explored whether photochemical products can alter the equilibrium temperature profile of the atmosphere. In our presentation we will summarize the modeling approach employed to characterize 51 Eri b, explaining constraints on the planet’s effective temperature, gravity, and atmospheric composition and also present results of our studies of atmospheric photochemistry. We will discuss whether photochemical hazes could indeed be responsible for the particulate opacity that apparently sculpts the spectrum of the planet.
Contributing Teams: The Gemini Planet Imager Exoplanet Survey Team

Stefanie Rätz (ESA):   Observations of an Extreme Planetary System

Almost 500 planet host stars are already known to be surrounded by more than one planet. Most of them (except HR8799) are old and all planets were found with the same or similar detection method. We present an unique planetary system. For the first time, a close in transiting and a wide directly imaged planet are found to orbit a common host star which is a low mass member of a young open cluster. The inner candidate is the first possible young transiting planet orbiting a previously known weak-lined T-Tauri star and was detected in our international monitoring campaign of young stellar clusters. The transit shape is changing between different observations and the transit even disappears and reappears. This unusual transit behaviour can be explained by a precessing planet transiting a gravity-darkened star. The outer candidate was discovered in the course of our direct imaging survey with NACO at ESO/VLT. Both objects are consistent with a <5 Jupiter mass planet. With ~2.4 Myrs it is among the youngest exoplanet systems. Both planets orbit its star in very extreme conditions. The inner planet is very close to its Roche limiting orbital radius while the outer planet is far away from its host star at a distance of ~660 au. The detailed analysis will provide important constraints on planet formation and migration time-scales and their relation to protoplanetary disc lifetimes. Furthermore, this system with two planets on such extreme orbits gives us the opportunity to study the possible outcome of planet-planet scattering theories for the first time by observations. I will report on our monitoring and photometric follow-up observations as well as on the direct detection and the integral field spectroscopy of this extreme planetary system.

Alice Zurlo (U Diego Portales):   New SPHERE Results on the Planetary System around HR8799

Since its discovery in 2008, the multi-planetary system around HR8799 has become a unique testbed for planet formation theories at large orbital radii and the study of non-irradiated planetary atmospheres. We present new SPHERE/IRDIS data in J, H, and K band, for the four planets HR8799bcde with SPHERE/IRDIS and YH-band spectra for planets d and e with SPHERE/IFS. We detect the closest planet HR8799e in J band for the first time. The astrometry gathered for three epochs of observation set new constraints on a hypothetical planet f. We combine the SPHERE photometry and spectra to demonstrate that the 1-5 µm spectral-energy distribution (SED) of the planets e and d can be represented by those of dusty -and young - L7 dwarfs. We show that the two outermost planet SEDs are well reproduced by the spectra of peculiar early-T dwarfs reddened by refractory grain opacities. This demonstrates that the planet peculiar photometric properties are dominated by the effect of dust, and suggests that the planets c, and then b, are less massive that the two innermost ones.
Contributing Teams: SPHERE team

Christoph Baranec (U Hawaii):   LGS-AO Imaging of Every Kepler Planet Candidate: the Robo-AO KOI Survey

The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star with laser adaptive optics imaging, to search for blended nearby stars which may be physically associated companions and/or responsible for transit false positives. We will present the results from searching for companions around over 3,000 Kepler planet hosts in 2012-2015. We will describe our first data release covering 715 planet candidate hosts, and give a preview of ongoing results including improved statistics on the likelihood of false positive planet detections in the Kepler dataset, many new planets in multiple star systems, and new exotic multiple star systems containing Kepler planets. We will also describe the automated Robo-AO survey data reduction methods, including a method of using the large ensemble of target observations as mutual point-spread-function references, along with a new automated companion-detection algorithm designed for extremely large adaptive optics surveys. Our first data release covered 715 objects, searching for companions from 0.15” to 2.5” separation with contrast up to 6 magnitudes. We measured the overall nearby-star-probability for Kepler planet candidates to be 7.4+/-1.0%, and we will detail the variations in this number with stellar host parameters. We will also discuss plans to extend the survey to other transiting planet missions such as K2 and TESS as Robo-AO is in the process of being re-deployed to the 2.1-m telescope at Kitt Peak for 3 years and a higher-contrast Robo-AO system is being developed for the 2.2-m UH telescope on Maunakea.

3:30 PM — Coffee Break

4:00 PM — Direct Imaging II    [Chair: Jennifer Patience]

Katherine Follette (Stanford):    An Accreting Protoplanet: Confirmation and Characterization of LkCa15b

We present a visible light adaptive optics direct imaging detection of a faint point source separated by just 93 milliarcseconds (~15 AU) from the young star LkCa 15. Using Magellan AO's visible light camera in Simultaneous Differential Imaging (SDI) mode, we imaged the star at Hydrogen alpha and in the neighboring continuum as part of the Giant Accreting Protoplanet Survey (GAPplanetS) in November 2015. The continuum images provide a sensitive and simultaneous probe of PSF residuals and instrumental artifacts, allowing us to isolate H-alpha accretion luminosity from the LkCa 15b protoplanet, which lies well inside of the LkCa15 transition disk gap. This detection, combined with a nearly simultaneous near-infrared detection with the Large Binocular Telescope, provides an unprecedented glimpse at a planetary system during epoch of planet formation. [Nature result in press. Please embargo until released]
Contributing Teams: Magellan Adaptive Optics, LBTI

Paul Kalas (UC Berkeley):   Extreme Imaging: Revealing the Structure of Debris Disks on Solar Systems Scales with GPI

A new generation of extreme adaptive optics systems enables an unprecedented exploration of dusty debris disks on solar system scales. Here we review the new science derived from over a dozen debris disks imaged in total intensity and polarized intensity with the Gemini Planet Imager (GPI). These early results typically reveal narrow belts of material with evacuated regions roughly 50 AU in radius and with subtle asymmetries in structure. In many cases, complementary wider field images obtained with the Hubble Space Telescope uncover more extreme asymmetries in the distribution of dust on 100’s of AU scales. We will discuss the possible causes of these asymmetries, such as the dynamical upheavals that can occur via internal or external perturbations. In a few cases, a gas giant planet has also been imaged in the system, raising new questions about the possible dynamical co-evolution of exoplanets and debris disks.
Contributing Teams: The Gemini Planet Imager Exoplanet Survey Team (PI Macintosh)

Mark Booth (PUC):   Resolving the Planetesimal Belt of HR 8799 with ALMA

HR 8799 is well known for being the only star to host multiple planets discovered through direct imaging. HR 8799 also hosts a debris disc first discovered by IRAS. This disc was one of the few resolved by Spitzer showing that dust is present out to a few thousand AU. The Spitzer data also showed that there must be multiple components to the dust both inside and outside the orbits of the planets. Naturally, this system has been a prime target for observations from various telescopes in recent years. We have observed the system with ALMA in band 6 (1340µm), detecting the disc at high resolution. For the first time we resolve the inner edge of the cold planetesimal belt and can determine its inclination at much higher precision than previous observations. I will discuss how these results compare to the previous observations and what these new results can tell us about the planets in the system.

Thayne Currie (NAOJ):   Extreme Exoplanet Direct Imaging: New Results with GPI and SCExAO and the Path to Imaging Another Earth

We describe the discovery of a bright, young Kuiper belt-like debris disk around HD 115600, a $\sim$ 1.4--1.5 M$_\mathrm{\odot}$, $\sim$ 15 Myr old member of the Sco-Cen OB Association. Our H-band coronagraphy/integral field spectroscopy from the \textit{Gemini Planet Imager} shows the ring has a (luminosity scaled) semi major axis of ($\sim$ 22 AU) $\sim$ 48 AU, similar to the current Kuiper belt. The disk appears to have neutral scattering dust, is eccentric (e $\sim$ 0.1--0.2), and could be sculpted by analogues to the outer solar system planets. Spectroscopy of the disk ansae reveal a slightly blue to gray disk color, consistent with major Kuiper belt chemical constituents, where water-ice is a very plausible dominant constituent. Besides being the first object discovered with the next generation of extreme adaptive optics systems (i.e. SCExAO, GPI, SPHERE), HD 115600's debris ring and planetary system provides a key reference point for the early evolution of the solar system, the structure and composition of the Kuiper belt, and the interaction between debris disks and planets.

Mickaël Bonnefoy (IPAG):   Direct Imaging of the Cold Jovian (?) Companion GJ504b with VLT/SPHERE

In 2008, the Subaru/SEEDS survey reported the direct imaging discovery of a Jovian exoplanet around the Sun-like star GJ 504. With a mass of 3-10 MJup and projected separation of 43.5 AU, this object challenges the core-accretion paradigm. This is the only known nearly mature (age >> 50 Myr) gas giant planet imaged so far. The very low (500 K) estimated temperature of the object makes it a benchmark for the study of the physical and chemical processes at play into the non-irradiated atmospheres of gas giants. We will present new SPHERE dual-band imaging data on the system gathered from 0.95 to 2.25 microns. The data enable to detect the companion and complete its spectral energy distribution. We use them to refine the effective temperature, surface gravity, and metallicity estimates for the object. This in turns enables to discuss the nature of the companion. We also set constraints on additional companions in the system.
Contributing Teams: Mickaël BONNEFOY and the SPHERE consortium

Jacqueline Faherty (Carnegie DTM):   Extreme Planet-Like Systems: Brown Dwarfs at the Exoplanet Mass Boundary

Brown dwarfs have long been the observational anchors for our theoretical understanding of giant gas planets. Recent studies have uncovered a population of nearby young sources that rival the age and mass of many planetary mass companions. From detailed observations, we postulate that objects in this young population have dynamic atmospheres ripe with exotic, thick condensate cloud species that drive extreme photometric and spectroscopic characteristics. In this talk I will review how we are using these so-called exoplanet analogs to establish luminosity, temperature, age, and mass relations for brown dwarf into planetary mass objects.
Contributing Teams: Jonathan Gagne; Kelle Cruz; Emily Rice

Christiane Helling (St Andrews):   Plasma Processes in Cloud-forming Exoplanet and Brown Dwarf Atmospheres

The increasing number of observations of cyclotron emission, possible chromospheric emission, and potential aurorae suggests that high energy processes occur also in, or are associated with ultra-cool, cloud-forming atmospheres like in extrasolar planets and brown dwarfs. While a magnetic field is primordial to brown dwarfs and most planets, free charges in form of electrons need to be continuously produced to allow the necessary magnetic coupling for cyclotron emission to occur or for the formation of a chromosphere and possible magnetically driven winds to emerge. This is particularly critical for free floating objects not bathed in the wind of a host or companion star. We perform a reference study for late M-dwarfs, brown dwarfs and giant gas planets to identify which ultra-cool objects are most susceptible to plasma and magnetic processes. We utilise the Drift-Phoenix model grid where the local atmospheric structure is determined by the global parameters Teff , log(g) and metalicity [M/H]. For this reference study, thermal ionisation is considered only. Our results show that it is not unreasonable to expect Halfa or radio emission to origin from ultra-cool atmospheres as in particular the rarefied upper parts of the atmospheres can be magnetically coupled despite having low degrees of thermal gas ionisation. The minimum threshold for the magnetic flux density required for electrons and ions to be magnetised is well above typical values of the global magnetic field of brown dwarfs and giant gas planets. Such atmospheres could therefore drive, e.g., auroral emission without the need for a companion's wind or an outgassing moon. The reference study is based on thermal emission and provides therefore a lower limit for plasma effects in late M-dwarfs, brown dwarfs and giant gas planets. We have shown that non-equilibrium processes like cloud discharges in form of lightning and coronal discharges, high wind speeds and cosmic rays increase the local electron budget substantially.
Contributing Teams: The LEAP team


7:30 — 9:00 PM Poster Viewing Session


8:30 AM — Planet Formation    [Chair: Kaitlin Kratter]

Eugene Chiang (UC Berkeley):   Earths, Super-Earths, and Jupiters

We review our understanding of the formation of rocky planets to gas giants as informed by Kepler and radial velocity surveys. We highlight the decisive role played by the solid surface density of the parent disk in determining final outcomes: planet masses, compositions, and orbital spacings. An analytic theory for how rocky cores acquire their gas envelopes is compared against numerical simulations. For the most part, data and theory appear consistent with in-situ formation of Earths and super-Earths and a migratory origin for warm and hot Jupiters.

Ruobing Dong (UC Berkeley):   Spiral Arms in Scattered Light Images of Protoplanetary Disks

In the past few years, resolved observations with high angular resolution have revealed rich structures in gaseous protoplanetary disks. Among all discoveries, one of the most prominent is the giant double-spiral structure, found in MWC 758, SAO 206462, and HD 100453. The NIR images of these disks taken by Subaru/HiCIAO, VLT/NACO, and VLT/SPHERE showed two spiral arms at tens of AU from the center. The arms are very open with large pitch angles, and are in a nearly m=2 rotational symmetry. Although planets are known to be able to excite density waves in protoplanetary disks, fitting observations with linear theory of the density wave demands unreasonably big scale height in the disk, thus temperature, in order to make the arms as open as observed (and no need to mention the coincidence that they all have two nearly m=2 arms). Using 3D hydro and radiative transfer simulations, we find that a massive perturber (giant planet, brown dwarf, or stellar mass companion) can excite multiple spiral arms in the density structure, and the arms inside the perturber's orbit are very prominent in NIR scattered light images, in striking similarity with observations. Very recently, the perturber was found for the first time in the HD 100453 disk, as a M dwarf companion. This gives us great confidence of our models, and suggests that the double spirals in the other two objects, MWC 758 and SAO 206462, are very likely to be excited in a similar way, by a currently unseen perturber outside the arms. In particular, by measuring the angular distance between the two arms and comparing it with our models, we determine that the perturber in SAO 206462 is about 6 Jupiter mass.
Contributing Teams: Eugene Chiang, Jeffrey Fung, Cassandra Hall, Roman Rafikov, Ken Rice, James Stone, Zhaohuan Zhu

Katherine Kretke (SWRI):   Forming the Solar System from Pebbles

In recent years, theories surrounding the formation of small-bodies and planets have been undergoing a radical shift. Particles with stopping times comparable to their orbital times, often called "pebbles" (although they range from sub-centimeter to meter sizes), interact with gaseous protoplanetary disks in very special ways. This allows them to be not only be concentrated, allowing them to gravitationally collapse and directly produce the planetesimal building blocks of planetary systems, but also later be efficiently accreted on to these planetesimals, rapidly producing larger planets. Here we present simulations using the planet formation code LIPAD, which can follow the dynamical evolution of planetary system all the way from pebbles and planetesimals to mature planetary systems. We show how pebble accretion can explain the observed structure of our Solar System, by forming a system of giant planets, ice giants, and a system of terrestrial planets; even providing an explanation the for the low mass of Mars and of the Asteroid Belt.

Elisa Quintana (NASA Ames):   When Worlds Collide: How Collisions and Fragmentation affect Terrestrial Planet Formation

The late stages of terrestrial planet formation are dominated by giant impacts that collectively influence the growth, dynamical stability, composition and habitability of any planets that form. Numerical models designed to explore these late stage collisions have been limited in two major ways. First, nearly all N-body models have assumed that all collisions lead to perfect accretion. Second, many of these studies lack the large number of realizations needed to account for the chaotic nature of these N-body systems. We have recently developed an N-body algorithm, based on the widely-used Mercury integration package, that includes a state-of-the-art collision model that allows fragmentation and hit-and-run collisions. Using this new model, we have performed hundreds of simulations of late stage terrestrial planet formation around a Sun-like star with Jupiter and Saturn analogs. We will present these results and compare them to a set of 140 simulations using the standard perfect-accretion model. Over 90% of our fragmentation simulations produced an Earth-analog and we will discuss how we quantify the collisions that led to their formation in order to study their bulk compositions and likelihood of accreting and retaining an atmosphere and oceans.
Contributing Teams: Barclay, Thomas; Borucki, William; Chambers, John; Rowe, Jason

Eiichiro Kokubo (NAOJ):   Formation of Close-in Terrestrial Planets by Giant Impacts: The Basic Scaling Laws

The recent exoplanet surveys have shown that small close-in planets are more common than hot Jupiters. Most of them are considered as terrestrial (rocky) planets. Thus it becomes increasingly important to generally understand the formation of terrestrial planets. In the standard scenario of terrestrial planet formation, the final stage is the giant impact stage after the dispersal of a gas disk where protoplanets or planetary embryos collide with one another to complete planets. In the present paper, we investigate the in-situ formation of close-in terrestrial planets including super-Earths by giant impacts using N-body simulations. The goal of this project is to obtain the basic scaling laws of close-in terrestrial planet formation as a function of properties of protoplanet systems. We systematically change the system parameters of initial protoplanet systems and investigate their effects on the final planets. We find that in general non-resonant dynamically cold compact systems are formed. The orbits of planets are less eccentric and inclined and the orbital separations of adjacent planets are smaller, compared with those formed in the outer disk. The masses of all planets are almost comparable. These properties are natural outcomes of giant impacts in the inner disk. In the inner disk the ratio of the physical radius to the Hill radius is large, in other words, gravitational scattering is relatively less effective compared with that in the outer disk. Thus protoplanets are less mobile and accretion proceeds relatively locally, which leads to formation of dynamically cold compact systems. The typical mass of the largest planet increases almost linearly with the total mass of protoplanets, while the number of planets per radial width decreases. On average the system angular momentum deficit increases with the total system mass, while the mean orbital separation of adjacent planets decreases.

Konstantin Batygin (Caltech):   Origins of Hot Jupiters, Revisited

Hot Jupiters, giant extrasolar planets with orbital periods less than ~10 days, have long been thought to form at large radial distances (a > 2AU) in protostellar disks, only to subsequently experience large-scale inward migration to the small orbital radii at which they are observed. Here, we propose that a substantial fraction of the hot Jupiter population forms in situ, with the Galactically prevalent short-period super-Earths acting as the source population. Our calculations suggest that under conditions appropriate to the inner regions of protostellar disks, rapid gas accretion can be initiated for solid cores of 10-20 Earth masses, in line with the conventional picture of core-nucleated accretion. This formation scenario leads to testable consequences, including the expectation that hot Jupiters should frequently be accompanied by additional planets, reminiscent of those observed in large numbers by NASA’s Kepler Mission and Doppler velocity surveys. However, dynamical interactions during the early stages of planetary systems' evolutionary lifetimes tend to increase the mutual inclinations of exterior, low-mass companions to hot Jupiters, making transits rare. High-precision radial velocity monitoring provides the best prospect for their detection.

10 AM — Coffee Break

10:30 AM — Structure and Evolution    [Chair: Emily Rauscher]

Ruth Murray-Clay (UC Santa Barbara):   Large-Scale Structures of Planetary Systems

A class of solar system analogs has yet to be identified among the large crop of planetary systems now observed. However, since most observed worlds are more easily detectable than direct analogs of the Sun's planets, the frequency of systems with structures similar to our own remains unknown. Identifying the range of possible planetary system architectures is complicated by the large number of physical processes that affect the formation and dynamical evolution of planets. I will present two ways of organizing planetary system structures. First, I will suggest that relatively few physical parameters are likely to differentiate the qualitative architectures of different systems. Solid mass in a protoplanetary disk is perhaps the most obvious possible controlling parameter, and I will give predictions for correlations between planetary system properties that we would expect to be present if this is the case. In particular, I will suggest that the solar system's structure is representative of low-metallicity systems that nevertheless host giant planets. Second, the disk structures produced as young stars are fed by their host clouds may play a crucial role. Using the observed distribution of RV giant planets as a function of stellar mass, I will demonstrate that invoking ice lines to determine where gas giants can form requires fine tuning. I will suggest that instead, disk structures built during early accretion have lasting impacts on giant planet distributions, and disk clean-up differentially affects the orbital distributions of giant and lower-mass planets. These two organizational hypotheses have different implications for the solar system's context, and I will suggest observational tests that may allow them to be validated or falsified.

Eve Lee (UC Berkeley):   Breeding Super-Earths and Birthing Super-Puffs in Transitional Disks

The riddle posed by super-Earths (1--4 Earth radii, 2--20 Earth masses) is that they are not Jupiters: their core masses are large enough to trigger runaway gas accretion, yet somehow super-Earths accreted atmospheres that weigh only a few percent of their total mass. We show that this puzzle is solved if super-Earths formed late, as the last vestiges of their parent gas disks were about to clear. This scenario would seem to present fine-tuning problems, but we show that there are none. Ambient gas densities can span many orders of magnitude, and super-Earths can robustly emerge with percent-by-weight atmospheres after ~0.1--1 Myr. We propose that 1) close-in super-Earths form in situ, because their cores necessarily coagulate in gas-poor environments—gas dynamical friction must be weakened sufficiently to allow constituent protocores to cross orbits and merge; 2) super- Earths acquire their atmospheres from ambient wisps of gas that are supplied from a diffusing outer disk. The formation environment is reminiscent of the largely evacuated but still accreting inner cavities of transitional protoplanetary disks. We also 3) address the inverse problem presented by super-puffs: an uncommon class of short- period planets seemingly too voluminous for their small masses (4--10 Earth radii, 2--6 Earth masses). Super-puffs most easily acquire their thick atmospheres as dust-free, rapidly cooling worlds outside ~1 AU where nebular gas is colder, less dense, and therefore less opaque. Unlike super-Earths which can form in situ, super-puffs probably migrated in to their current orbits; they are expected to form the outer links of mean-motion resonant chains, and to exhibit greater water content.

Tristan Guillot (OCA):   Internal Structures and Compositions of Giant (Exo)planets

One can now attempt to determine the abundances of key species in the atmospheres of exoplanets, in particular hot Jupiters. In parallel, the knowledge of the densities of these exoplanets informs us on their bulk composition in terms of amounts of dense material (rocks and ices) compared to light ones (hydrogen and helium). Linking these constraints seems natural and, intuitively, one would expect dense planets to contain more heavy elements in their atmospheres. However, several physical processes, in particular the formation of a central core, its gradual erosion and the growth of a deep outer radiative zone, could decouple partially or even completely interior and atmospheric composition. The latter will also depend on how heavy elements were delivered to the planet. Close to us, measurements performed in the atmosphere of Jupiter (and to some extent in Saturn) already provide us with important clues: The high enrichment in carbon coupled to a more modest but significant enrichment in noble gases indicates that solids and gas-species followed different routes. Jupiter obtained its solids probably as a core and via pebble accretion and captured disk gas that had lost part of its hydrogen and helium. The elements originally solid in the disk but fluid in the planetary interior were at least partially mixed upward to account for the present day atmospheric composition. This simple scenario can be tested. The comparison of bulk and atmospheric compositions of hot Jupiters of different masses will tell us the importance of mixing. Measurements by the Juno spacecraft at Jupiter starting in July 2016 will help us constrain the abundance of water, a key element to understand how the solids were captured.

Dimitar Sasselov (Harvard):   Extreme Water: Characterizing Exoplanets with Excess Bulk Water Interiors

A number of planets with radii of 1 - 2.5 Earth radius have measured mean densities that allow more than 20% of their bulk interior to be composed of water. How do planets with solid-state water mantles modulate the fluxes of gases reaching the surface? What should we expect about the composition of their evolved atmospheres? I review theoretical models of the interiors and near-surface layers that constrain the fluxes of major gases (in and out) and resulting atmospheric compositions. The results have implications for observational characterization of rocky versus water planets, when the density alone is not enough, as well as the search for biosignatures and habitability.

Diana Valencia (U Toronto):   Ohmic Dissipation in Mini-Neptunes

In the quest of characterizing low-mass exoplanets, it is important to consider all sources that may contribute to the interpretation of planetary composition given mass and a radius measurements. While it has been firmly established that inferring the composition of super-Earths and mini-Neptunes suffers from the inherent problem of compositional degeneracy, the effect from ohmic dissipation on these planets and its connection to compositional interpretation has not been studied so far. Ohmic dissipation is arguably the leading theory that aims to explain the large radii seen in highly-irradiated exo-Jupiters. In this study, we determine the strength of ohmic dissipation on mini-Neptunes and its effect on their H/He envelope structure as a function of insolation temperature and planetary mass. We find that ohmic dissipation is strong enough to halt the contraction of mini-Neptunes during their thermal evolution and therefore, inflate their radii in comparison to planets that do not suffer dissipation. This means that the radius of highly irradiated of this class of planets may be explained by the presence of volatiles and ohmic dissipation. In other words, there is a trade-off between ohmic dissipation and H/He content for hot mini-Neptunes.

Alexandre Santerne (U Porto):   The Physical Properties of Giant Exoplanets within 400 Days of Period

At a time when small planets in the habitable zone are found, not all the questions about giant planets have been answered. For example, their formation, migration and evolution are far from being fully understood. In this context, the Kepler space mission is providing unprecedented constraints to theories by probing transiting giant planets in a wide range of orbital periods. In this talk, we will present the results of a 6-year spectroscopic survey with the SOPHIE spectrograph of the transiting giant-planet candidates detected by Kepler within 400 days of period. First, we will describe the giant-planet candidate sample from the Kepler catalog and our spectroscopic observations which allowed us to screen out more than half of the candidates as false positives. Then, we will present the occurrence rate of giant planets, based on our sample cleaned from fake transiting planets, and compare it with other surveys. Finally, we will discuss the physical properties of the giant transiting planets within 400 days of period and compare them with predictions from planet-synthesis models.

Robin Canup (SWRI):   On the Expected Properties of Exomoons

The potential discovery of exomoons is important, as they could provide constraints on their host planets’ formation, and large exomoons may represent potentially habitable environments. Detection of exomoons is extremely challenging. However, upper limits on exomoon masses have now been determined for a few dozen planets (Kipping et al. 2015), and additional constraints and/or detections are anticipated in the next several years. In our solar system, regular satellites are thought to have originated by two main processes: giant impacts and co-accretion. The origin of moons by collisions into solid planets is reasonably well-understood. Depending primarily on the impact angle and the mass of the impactor compared to the target, collisions can produce a broad range of satellite-to-planet mass ratios, Msat/Mp, ranging from tiny moons to relatively massive satellites such as the Moon (Msat/Mp = 0.01; e.g., Canup 2004) and Pluto’s Charon (Msat/Mp = 0.12; e.g., Canup 2005). In contrast, the satellite systems of the gas planets in our solar system all have Msat/Mp ~10^{-4}. This similarity is striking given what were presumably different accretion histories for each of these planets. It has been shown that a common satellite system mass ratio results when satellites co-accrete within disks produced by gas and solids inflowing to a planet, with the predicted value of (Msat/Mp) depending rather weakly on the ratio of the disk’s gas viscosity parameter to the gas-to-solids ratio in the inflow (Canup & Ward 2006). The transition between these two modes of origin is unclear, but could reasonably occur once a planet grows large enough to accrete substantial gas through a circumplanetary disk (e.g., Mp ~ 5 to 10 Earth masses; e.g., Machida et al. 2008; 2010). Alternative satellite-forming mechanisms are also possible, e.g., intact capture. However to date, exomoon upper limits appear consistent with expectations based on formation by impact or co-accretion. If exomoons form primarily by these two processes, the most likely hosts of a Mars-sized exomoon would be predominantly solid planets of several Earth masses, or gas giants substantially more massive than Jupiter.

Free Afternoon and Evening


8:30 AM — Atmospheres I    [Chair: Sara Seager]

Adam Showman (U Arizona):   Atmospheric Circulation of Warm and Hot Jupiters: Effect of Non-Synchronous Rotation and Stellar Irradiation

Efforts to characterize and model extrasolar giant planet (EGP) atmospheres have so far emphasized planets within ~0.05 AU of their stars. Despite this focus, known EGPs now populate nearly a continuum of orbital separations from canonical hot Jupiter values (~0.03-0.05 AU) out to 1 AU and beyond. Unlike typical hot Jupiters, these more distant EGPs will not in general be synchronously rotating and may exhibit a range of rotation rates. In anticipation of observations of this wider population, we here present state-of-the-art atmospheric circulation models including realistic non-grey radiative transfer to explore the dynamical regime that emerges over a broad range of rotation rates and incident stellar fluxes appropriate for warm and hot Jupiters. We find that the circulation resides in one of two basic regimes. The circulation for canonical hot Jupiters exhibits a broad, fast superrotating (eastward) equatorial jet driven by the strong day-night heating contrast, with westward mean flow at high latitudes and large day-night temperature differences. Non-synchronous rotation exerts a significant influence on the jet structure and temperature patterns. Under the less-strongly irradiated conditions appropriate to warm Jupiters, however, the circulation transitions to a vastly different dynamical regime: the day-night heating gradient becomes less important, and baroclinic instabilities emerge as a dominant player, leading to eastward zonal jets in the midlatitudes, with significant equator-to-pole temperature differences, minimal temperature variations in longitude, and, in many cases, weak windflow at the equator. We present infrared (IR) light curves and spectra of these models, which depend significantly on incident stellar flux and rotation rate. This provides a way to identify the regime transition in future observations. In some cases, IR light curves can provide constraints on the rotation rate of nonsynchronously rotating planets.

Laura Kreidberg (U Chicago):   A New Angle on Atmosphere Characterization of Giant Exoplanets

Detailed characterization of exoplanets has begun to yield constraints on their atmospheric properties that rival our knowledge of the Solar System planets. These measurements provide unique insight into planet formation and evolution because atmospheres are a rich record of protoplanetary disk chemistry. In this talk, I will present new constraints on hot Jupiter atmospheric composition and thermal structure from two intensive Hubble Space Telescope observational campaigns targeting WASP-12b and WASP-103b. For WASP-12b, we obtained a very precise near-infrared spectrum that exhibits water features at high confidence (>7σ). This detection marks the first spectroscopic identification of a molecule in the planet’s atmosphere and implies that it has solar composition, ruling out carbon-to-oxygen ratios greater than unity. For WASP-103b, I will present preliminary results from the new technique of phase-resolved spectroscopy that constrain the planet’s temperature structure, dynamics, and energy budget. Taken together, these results highlight the importance of synthesizing multiple observing angles - emission spectroscopy, transmission spectroscopy, and phase curves - to obtain precise, robust constraints on the chemistry and physics of exoplanet atmospheres.

Björn Benneke (Caltech):   Measurements of Water Absorption in the Warm Exo-Uranus GJ 3470b

The discovery of short-period planets with masses and radii intermediate between Earth and Neptune was one of the biggest surprises in the brief history of exoplanet science. These “super-Earths” and “sub-Neptunes” are an order of magnitude more abundant than close-in giant planets. Despite this ubiquity, we know little about their typical compositions and formation histories. Spectroscopic transit observations can shed new light on these mysterious worlds by probing their atmospheric compositions. In this talk, we will give an overview of our ongoing 124-orbit (200-hour) Hubble Space Telescope program to reveal the chemical diversity and formation histories of super-Earths. This unprecedented survey will provide the first comprehensive look at this intriguing new class of planets ranging from 1 Neptune mass and temperatures close to 2000K to a 1 Earth mass planet near the habitable zone of its host star. In this talk, I will discuss the scope of the program and present early science results including measurements of water absorption in the atmosphere of the warm exo-Uranus GJ3470b.

Jean-Michel Désert (U Amsterdam):   First Survey of Transiting Exoplanet Atmospheres using a Multi-Object Spectrograph

We present results from the first comprehensive survey program dedicated to probing transiting exoplanet atmospheres using transmission spectroscopy with a multi-object spectrograph (MOS). Our three-year survey focused on nine close-in giant planets for which the wavelength dependent transit depths in the visible were measured with Gemini/GMOS. In total, about 40 transits (200 hours) have been secured, with each exoplanet observed on average during four transits. This approach allows for a high spectrophotometric precision (200-500 ppm / 10 nm) and for a unique and reliable estimate of systematic uncertainties. We present the main results from this survey, the challenges faced by such an experiment, and the lessons learnt for future MOS observations and instrument designs. We show that the precision achieved by this survey permits us to distinguish hazy atmospheres from cloud-free scenarios. We lay out the challenges that are in front of us whilst preparing future atmospheric reconnaissance of habitable worlds with multi-object spectrographs.
Contributing Teams: Jean-Michel Desert

Knicole Colon (NASA Ames):   Scorched Planets: Understanding the Structure and Climate of Hot Jupiter Atmospheres

Radial velocity and transit surveys have revealed that hot Jupiters are intrinsically rare in the Galaxy. These extreme examples of extrasolar planets have been the subject of many studies to date, but their formation and evolution are still shrouded in mystery. I will present results from a large ground-based survey to study the atmospheres of hot Jupiters via their secondary eclipses in the near-infrared. Such observations provide us with a direct measurement of thermal emission from a planet’s day-side, allowing us to probe the connection between the atmospheric structure and climate deep in their atmospheres, as well as the irradiation from their host star. I will present results obtained for several hot Jupiters using the wide-field camera WIRCam on the 3.6m Canada-France-Hawaii-Telescope (CFHT). The sample of hot Jupiters observed to date in the CFHT survey spans a range of planetary parameters (e.g. temperatures and densities) and also includes several new exotic discoveries from the KELT transit survey, such as a planet in a hierarchical triple stellar system as well as a planet with a very rapidly rotating host star. Results from the CFHT survey will be combined with those from an ongoing survey of hot Jupiter eclipses in the southern hemisphere using the 3.9m Anglo-Australian Telescope as well as an upcoming survey using the 4m Mayall Telescope at Kitt Peak National Observatory. The combined survey will be the largest homogeneous study of this kind to date, and it will provide us with the congruent observations of a significant number of unique planets in eclipse. These observations will ultimately allow a comprehensive statistical analysis of the diversity of hot Jupiter atmospheres via their near-infrared eclipses. In addition, this project will identify legacy targets for comparative exoplanetology using next-generation facilities such as the James Webb Space Telescope.

Sarah Ballard (MIT):   Exploring Links Between Orbital Dynamics and Atmospheres in Kepler M Dwarf Planetary Systems

The Solar System furnishes the most familiar planetary architecture: many planets, orbiting nearly coplanar to one another. However, the most common planetary systems in the Milky Way orbit much smaller M dwarf stars, and these may present a very different blueprint. The Kepler data set has furnished more than 100 exoplanets orbiting stars half the mass of the sun and smaller. Half of these planets reside in systems with at least one additional planet. The data much prefer a model with two distinct modes of planet formation around M dwarfs, which occur in roughly equal measure. One mode is one very similar to the Solar System in terms of multiplicity and coplanarity, and the other is very dissimilar. Given this so-called "Kepler Dichotomy," we examine the broadband transmission spectra (with data from Kepler and hundreds of hours of Spitzer observations) of dozens of M dwarf planets: half of which reside in one type of planetary system, and half in the other. Although the data set is too small and the observational uncertainty too large to characterize any one system alone, we examine ensemble trends between planetary dynamics and atmospheric content.

10 AM — Coffee Break

10:30 AM — Atmospheres II    [Chair: Christiane Helling]

Caroline Morley (UC Santa Cruz):   Seeing Through the Clouds: Thermal Emission & Reflected Light Spectra of Super-Earths

Vast resources have been dedicated to characterizing the handful of planets with radii between Earth’s and Neptune’s that are accessible to current telescopes. Observations of their transmission spectra have been inconclusive and do not constrain their atmospheric compositions. Of the planets smaller than Neptune studied to date, all have radii in the near-infrared consistent with being constant in wavelength, likely showing that these small planets are consistently enshrouded in thick hazes and clouds. We explore the types of clouds and hazes that can completely obscure transmission spectra and find that very thick, lofted clouds of salts or sulfides in high metallicity (1000× solar) atmospheres create featureless transmission spectra in the near-infrared. Photochemical hazes with a range of particle sizes also create featureless transmission spectra at lower metallicities. We present a path forward for understanding this class of small planets: by understanding the thermal emission and reflectivity of small planets, we can break the degeneracies and better constrain the atmospheric compositions. Cloudy thermal emission spectra have muted features more like blackbodies, and hazy thermal emission spectra have emission features caused by an inversion layer at altitudes where the haze forms. Analysis of reflected light from warm (~400-800 K) planets can distinguish cloudy planets, which have moderate albedos (Ag=0.05–0.20), from hazy planets, which are very dark (Ag=0.0–0.03). Reflected light spectra of cold planets (~200 K) accessible to a space-based visible light coronagraph may be the key to understanding small planets: they will have high albedos and large molecular features that actually allow them to be more easily characterized than the warmer transiting planets. We suggest a number of complementary observations to characterize super Earths, including transmission spectra of hot (~1000 K) targets, thermal emission spectra of warm targets using the James Webb Space Telescope (JWST), and high spatial resolution spectral observations of directly-imaged cold targets in reflected light. These observations may provide rich diagnostics of molecules and clouds in small planets, in contrast to the limited success to date.

Eliza Kempton (Grinnell College):   Clouds Composition in Super-Earth Atmospheres: Chemical Equilibrium Calculations

Attempts to determine the composition of super-Earth atmospheres have so far been plagued by the presence of clouds. Yet the theoretical framework to understand these clouds is still in its infancy. For the super-Earth archetype GJ 1214b, KCl, Na2S, and ZnS have been proposed as condensates that would form under the condition of chemical equilibrium, if the planet’s atmosphere has a bulk composition near solar. Condensation chemistry calculations have not been presented for a wider range of atmospheric bulk composition that is to be expected for super-Earth exoplanets. Here we provide a theoretical context for the formation of super-Earth clouds in atmospheres of varied composition by determining which condensates are likely to form, under the assumption of chemical equilibrium. We model super-Earth atmospheres assuming they are formed by degassing of volatiles from a solid planetary core of chondritic material. Given the atomic makeup of these atmospheres, we minimize the global Gibbs free energy of over 550 gases and condensates to obtain the molecular composition of the atmospheres over a temperature range of 350-3,000 K. Clouds should form along the temperature-pressure boundaries where the condensed species appear in our calculations. The super-Earth atmospheres that we study range from highly reducing to oxidizing and have carbon to oxygen (C:O) ratios that are both sub-solar and super-solar, thereby spanning a diverse range of atmospheric composition that is appropriate for low-mass exoplanets. Some condensates appear across all of our models. However, the majority of condensed species appear only over specific ranges of H:O and C:O ratios. We find that for GJ 1214b, KCl is the primary cloud-forming condensate at solar composition, in agreement with previous work. However, for oxidizing atmospheres, where H:O is less than unity, K2SO4 clouds form instead. For carbon-rich atmospheres with super-solar C:O ratios, graphite clouds additionally appear. At higher temperatures, clouds are formed from a variety of materials including metals, metal oxides, and aluminosilicates.

Jayne Birkby (Harvard):   Probing the Atmospheres of Brown Dwarfs and Reflected Light from Exoplanets

High-resolution spectroscopy (R>25,000) is a robust and powerful tool in the near-infrared characterization of exoplanet atmospheres. It has unambiguously revealed the presence of carbon monoxide and water in several hot Jupiters, measured the rotation rate of beta Pic b, and suggested the presence of fast day-to-night winds in one atmosphere. The method is applicable to transiting, non-transiting, and directly-imaged planets. It works by resolving broad molecular bands in the planetary spectrum into a dense, unique forest of individual lines and tracing them directly by their Doppler shift, while the star and tellurics remain essentially stationary. I will focus on two ongoing efforts to expand this technique. First, I will present new results on 51 Peg b revealing its infrared atmospheric compositional properties, then I will discuss an ongoing optical HARPS-N/TNG campaign (due mid October 2015) to obtain a detailed albedo spectrum of 51 Peg b at 387-691 nm in bins of 50nm. This spectrum would provide strong constraints on the previously claimed high albedo and potentially cloudy nature of this planet. Second, I will discuss preliminary results from Keck/NIRSPAO observations (due late September 2015) of LHS 6343 C, a 1000 K transiting brown dwarf with an M-dwarf host star. The high-resolution method converts this system into an eclipsing, double-lined spectroscopic binary, thus allowing dynamical mass and radius estimates of the components, free from astrophysical assumptions. Alongside probing the atmospheric composition of the brown dwarf, these data would provide the first model-independent study of the bulk properties of an old brown dwarf, with masses accurate to <5%, placing a crucial constraint on brown dwarf evolution models.

Matteo Brogi (U Colorado):   Rotation and Winds of Exoplanet HD 189733 b Measured with High-Resolution Transmission Spectroscopy

At the dawn of exoplanet science, the first discoveries revealed the existence of giant planets orbiting very close to their parent stars, called hot Jupiters. Early theories suggested that these planets should be tidally locked, although their spin rotation has never been measured directly. On top of rotation, hot Jupiters can show equatorial super-rotation via eastward jet streams and/or high-altitude winds flowing from the day- to the night-side hemisphere. All these patterns broaden and distort the planet spectral lines to an extent that is detectable with measurements at high spectral resolution. High-dispersion observations have recently excelled in robustly detecting molecules in the atmospheres of transiting and non-transiting hot Jupiters, and in measuring their relative abundances. Here the method is applied to the transmission spectrum of HD 189733 b, a Jupiter-size planet orbiting a K1-2V star in 2.2 days, observed around 2.3μm with CRIRES at the ESO Very Large Telescope. At a spectral resolution of R~100,000, the combined absorption of carbon monoxide and water vapor is detected in the planet spectrum at a confidence level of 7σ. The signal is obtained by cross correlating with theoretical spectra and it is maximized for a planet rotational velocity of 3.5+1.1-2.6 km/s. This corresponds to a planet rotational period of 1.7+4.9-0.4 days, consistent with the known orbital period of 2.2 days and therefore with tidal locking. Although planet rotations faster than 1.1 days can be ruled out at high confidence (3σ), sub-synchronous rotational velocities (Vrot < 2.7 km/s) or no-rotation are only marginally excluded (1.2σ). Finally, no significant day-to-night side winds are detected. When compared to the recent detection of sodium Doppler shifted by -8 km/s, this likely implies a strong wind shear between the atmospheric levels probed by these high-dispersion observations and the outermost atmospheric layers where the core of the sodium lines are formed.

Michael Liu ( U Hawaii):   Connecting Young Brown Dwarfs and Directly Imaged Gas-Giant Planets

Direct detections of gas-giant exoplanets and discoveries of young (~10-100 Myr) field brown dwarfs from all-sky surveys are strengthening the link between the exoplanet and brown dwarf populations, given the overlapping ages, masses, temperatures, and surface gravities. In light of the relatively small number of directly imaged planets and the modest associated datasets, the large census of young field brown dwarfs provides a compelling laboratory for enriching our understanding of both classes of objects. However, work to date on young field objects has typically focused on individual discoveries. We present a large comprehensive study of the youngest field brown dwarfs, comprising both previously known objects and our new discoveries from the latest wide-field surveys (Pan-STARRS-1 and WISE). With masses now extending down to ~5 Jupiter masses, these objects have physical properties that largely overlap young gas-giant planets and thus are promising analogs for studying exoplanet atmospheres at unparalleled S/N, spectral resolution, and wavelength coverage. We combine high-quality spectra and parallaxes to determine spectral energy distributions, luminosities, temperatures, and ages for young field objects. We demonstrate that this population spans a continuum in the color-magnitude diagram, thereby forming a bridge between the hot and cool extremes of directly imaged planets. We find that the extremely dusty properties of the planets around 2MASS J1207-39 and HR 8799 do occur in some young brown dwarfs, but these properties do not have a simple correspondence with age, perhaps contrary to expectations. We find young field brown dwarfs can have unusually low temperatures and suggest a new spectral type-temperature scale appropriate for directly imaged planets. To help provide a reference for extreme-contrast imaging surveys, we establish a grid of spectral standards and benchmarks, based on membership in nearby young moving groups, in order to calibrate gravity (age) and temperature diagnostics from near-IR spectroscopy. Finally, we use our data to critically examine the possibility that free-floating objects and companions may share different evolutionary histories, thereby complicating the brown dwarf-exoplanet connection.

Laurent Pueyo (STScI):   Infrared Spectrum and Orbital Properties of the Giant Planet Beta Pictoris b Obtained with GPI

We present a low-resolution multi-band spectrum of the planetary companion to the nearby young star beta Pictoris using the Gemini Planet Imager (GPI). GPI is designed to image and provide low-resolution spectra of Jupiter sized, self-luminous planetary companions around young nearby stars. While H-band is the primary workhorse for the GPI Exoplanet Survey, the instrument is capable of observing in the near infrared covering Y, J, H, and K bands. These observations of Beta Pic Pictoris b were taken covering multiple bands as part of GPI’s verification and commissioning phase in 2013 and 2014. Using atmospheric models along with the H-band data we recently reported an effective temperature of 1600-1700 K and a surface gravity of log (g) = 3.5-4.5 (cgs units). A similar exercise was also carried out by an independent team using the J band data, and did yield similar conclusions. These values agree well with ”hot-start” predictions from planetary evolution models for a gas giant with mass between 10 and 12 M Jup and age between 10 and 20 Myr. Here we revisit these conclusions in light of a joint analysis of these two datasets along with the longer wavelength GPI spectrum in K band, and present refined constraints on the atmospheric properties of this giant planet. In addition, we present an updated orbit for Beta Pictoris b based on astrometric measurements taken using commissioning and subsequent monitoring observations, spanning 14 months. The planet has a semi-major axis of 9.2 (+1.5 −0.4) AU, with an eccentricity e≤ 0.26. The position angle of the ascending node is Ω=31.75 deg±0.15, offset from both the outer main disk and the inner disk seen in the GPI image. We finally discuss these properties in the context of planet-disk dynamical interactions.
Contributing Teams: Jeffrey Chilcote; Maxwell A. Millar-Blanchaer; Travis Barman; Michael P. Fitzgerald; James R. Graham; James E. Larkin; Paul Kalas; Rebekah I. Dawson; Jason Wang; Marshall Perrin; Dae-Sik Moon; Bruce Macintosh And the GPIES Team

Brendan Bowler (Caltech):   Near-Infrared Spectroscopy of a Quadruple System Spanning the Stellar to Planetary Mass Regimes

High-contrast imaging surveys are discovering a growing number of brown dwarf companions and giant planets orbiting stars at wide separations between 10-100 AU, but the formation of these objects is poorly understood because multiple routes (disk instability, core accretion plus dynamical scattering, and cloud fragmentation) may contribute to this population. I will describe recent observations of 2M0441+2301 AabBab, a unique young (1-3 Myr) hierarchical quadruple system comprising a low-mass star, two brown dwarfs, and a planetary-mass companion in Taurus. Our near-infrared imaging and spectroscopy with Keck/NIRC2 and OSIRIS confirm the young age, late spectral type (~L1), and low temperature (~1800 K) of the faintest component, 2M0441+2301 Bb. With individual masses of ~200 Mjup, 35 Mjup, 19 Mjup, and 9.8 Mjup, 2M0441+2301 AabBab is the lowest-mass quadruple system known. Its hierarchical orbital architecture and mass ratios imply that it formed from the collapse and fragmentation of a molecular cloud core, demonstrating that planetary-mass companions can originate from a stellar-like pathway analogous to higher-mass quadruple star systems. More generally, cloud fragmentation may be an important formation pathway for the massive exoplanets that are now regularly being imaged on wide orbits.

Lunch Break

2:00 PM — Planets in and around Binaries I    [Chair: Ruth Murray-Clay]

Bill Welsh (San Diego State):   Kepler-47: A Three-Planet Circumbinary System

Kepler-47 is the most interesting of the known circumbinary planets. In the discovery paper by Orosz et al. (2012) two planets were detected, with periods of 49.5 and 303 days around the 7.5-day binary. In addition, a single "orphan" transit of a possible third planet was noticed. Since then, five additional transits by this planet candidate have been uncovered, leading to the unambiguous confirmation of a third transiting planet in the system. The planet has a period of 187 days, and orbits in between the previously detected planets. It lies on the inner edge of the optimistic habitable zone, while its outer sibling falls within the conservative habitable zone. The orbit of this new planet is precessing, causing its transits to become significantly deeper over the span of the Kepler observations. Although the planets are not massive enough to measurably perturb the binary, they are sufficiently massive to interact with each other and cause mild transit timing variations (TTVs). This enables our photodynamical model to estimate their masses. We find that all three planets have very low-density and are on remarkably co-planar orbits: all 4 orbits (the binary and three planets) are within ~2 degrees of one another. Thus the Kepler-47 system puts interesting constraints on circumbinary planet formation and migration scenarios.
Contributing Teams: Kepler TTV and EB Working Groups

Veselin Kostov (NASA Goddard):   KIC-5473556: the Largest and Longest-period Kepler Transiting Circumbinary Planet

We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of short-period CBPs orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet in the KIC-5473556 system has a very long orbital period (~1100 days) and was at conjunction only twice during the Kepler mission -- making it the longest-period transiting CBP at the time of writing. With a radius of nearly 12 REarth, it is also the largest such planet to date. It produced three transits in the light curve of KIC 5473556, one of them during a syzygy. The planet revolves around an ~11-day Eclipsing Binary consisting of two Solar-mass stars on a slightly inclined to the line of sight, mildly eccentric (ebin = 0.16) orbit. The CBP measurably perturbs the times of the stellar eclipses, allowing us to constrain its mass well. Here we present our spectroscopic and photometric observations of the target, discuss our analysis of the system, and outline the theoretical implications of our discovery.
Contributing Teams: Members of the Kepler EB and TTV Working Groups

Rachel Smullen (U Arizona):   The Architecture of Circumbinary Systems

Transiting circumbinary planets, as discovered by Kepler, provide unique insight into planet formation and planetary dynamics. These planets are low mass (about Neptune or smaller) and reside close to the stability limit of the binary. The question then becomes nature or nurture? Have circumbinary disks preferentially formed low mass, close in planets, or have dynamical processes sculpted the system into what we observe? We used N-body simulations to explore the impact of planet-planet scattering on the orbital architecture of four planetary populations around both single and binary stars. I will present the similarities and differences in the resultant planet populations. For instance, the final multiplicity is similar between single and binary stars, but planets in binary systems are much more likely to eject than collide. I will address the observable multiplicity and other unique characteristics our simulations have revealed. With this work and future observations, we will be able to better understand the underlying initial planetary distributions around binary stars and the formation mechanisms that allow these systems to form.

Trent Dupuy (UT Austin):   Orbital Architectures of Planet-Hosting Binary Systems

We present the first results from our Keck AO astrometric monitoring of Kepler planet-hosting binary systems. Observational biases in exoplanet discovery have long left the frequency, properties, and provenance of planets in most binary systems largely unconstrained. Recent results from our ongoing survey of a volume-limited sample of Kepler planet hosts indicate that binary companions at solar-system scales of 20–100 AU suppress the occurrence of planetary systems at a rate of 30–100%. However, some planetary systems do survive in binaries, and determining these systems' orbital architectures is key to understanding why. As a demonstration of this new approach to testing ideas of planet formation, we present a detailed analysis of the triple star system Kepler-444 (HIP 94931) that hosts five Ganymede- to Mars-sized planets. By combining our high-precision astrometry with radial velocities from HIRES and computational dynamical modeling, we discover an unexpected orbital architecture for this multi-planet, triple-star system. Finally, we preview results from our full statistical sample, such as tests of coplanarity between binary and planet orbits in single versus multi-planet systems.

David Bennett (Notre Dame):   The First Cold Circumbinary Planet Found by Microlensing

We present the first cold, circumbinary planet to be discovered by gravitational microlensing. This system consists of a slightly sub-Saturn mass planet orbiting a pair of M-dwarfs with a combined mass of about 0.7 solar masses. Although microlensing is more sensitive to circumbinary planets with orbital parameters near the stability limit, this system has a separation ratio of about 40:1, suggesting that circumbinary planets do not preferentially form near the stabilty limit.
Contributing Teams: MOA Collaboration; OGLE Collaboration; MicroFUN Collaboration; PLANET Collaboration

Ben Nelson (Northwestern):   ν Octantis: a Conjectured Circumprimary Retrograde Planet in a Spectroscopic Binary System

ν Octantis is a single-lined spectroscopic binary system consisting of a K-giant primary and a secondary orbiting near 1050 days. Radial velocity observations reveal an additional ~400 day periodicity with a semi-amplitude of 40 m/s. If this signal is planetary in nature, the ν Octantis system would be unique amongst all known exoplanet systems in that long-term stability can only be achieved if the orbit is retrograde with respect to the stellar companions (i.e. mutual inclination ~ 180°). Spectral line analyses suggest this signal is unlikely to be due to surface activity or pulsations (Ramm 2015). We also rule out an exotic scenario where the secondary itself is a binary. We report an analysis of 1437 radial velocity measurements taken with HERCULES at the Mt. John Observatory spanning nearly 13 years, 1180 being new iodine iodine-cell velocities (2009-2013). The sensitive orbital dynamics of the two-companion model allow us to constrain the three-dimensional orbital architecture directly from the observations. Posterior samples obtained from an n-body Markov chain Monte Carlo (Nelson et al. 2014) yields a mutual inclination of 158.4 ± 1.2°. None of these are dynamically stable beyond 10ˆ6 years. However, a grid search around the posterior sample suggests that they are in close proximity to a region of parameter space that is stable for at least 10ˆ6 years. If real, the tight orbital architecture here imposes a considerable challenge for formation of this dynamically extreme system.

3:30 PM — Coffee Break

4:00 PM — Planets in and around Binaries II    [Chair: Smadar Naoz]

Dan Fabrycky (U Chicago):   Dynamical Detection of Circumbinary Planets

The Kepler data revealed a population of transiting gas-giant planets orbiting around close binary stars, beginning with Kepler-16, a highlight of the Extreme Solar Systems II meeting. Due to the restrictive geometry requirements of transit detections, this population is highly observationally biased towards coplanarity. However, a third of those planets detectably perturb their host binary's eclipse times, such that they could have been recognized even without transits. Here we announce the detection of three non-transiting planets based on this dynamical technique. Apsidal precession due to the planet makes the primary and secondary eclipse periods differ, and in addition a short-term modulation of the binary's eclipse times reveals the planet's orbital period. Several planetary periods are observed for each system, buttressing the interpretation. Though the method is nearly equally sensitive to all orbital orientations, each planet orbits near its host binary's plane, suggesting this class of planets formed in the circumbinary nebula.
Contributing Teams: Kepler Eclipsing Binary and Transit Timing working groups

Johanna Teske (Carnegie):   Does Planet Formation Influence whether Binary Stars are Identical or Fraternal “Twins”?

Disentangling how an individual star’s atmospheric composition is affected by the chemistry and transport of disk material, the formation of planets, and its broader position in/motion through the Galaxy during its evolution is difficult. While initially suggested as a sign of accretion of H-depleted material onto the star, the giant planet-metallicity correlation is now established as a mostly primordial effect -- stellar composition affects planet formation. But is it still possible that planet formation may also alter host star composition? Previous studies hinted at a few cases of compositional differences between stars in binary systems, and now high-precision abundance analyses are exploring this possibility in systems known to host planets. I will discuss the important role binary host stars have to play in extending correlations between stellar composition and the presence/type of planets that form, including brand new (not yet published!) results.
Contributing Teams: Ivan Ramirez (UT Austin), Sandhya Khanal (UT Austin), Katia Cunha (Observatorio Nacional), Simon Schuler (University of Tampa), Verne Smith (NOAO), Luan Ghezzi (Observatorio Nacional)

Claude Mack (Leibnitz Inst):   Constraining Planet Formation from Detailed Chemical Abundances of Planet-Hosting Wide Binary Stars

We present a detailed chemical abundance analysis of planet-hosting wide binary systems. Each of these binary systems consists of two stars with similar spectral types (ranging from G2V - K2V), and in each system, at least one star hosts a giant planet with an orbital pericenter ~< 0.5 AU. We examine the photospheric abundances of the host stars to determine if they have ingested rocky planetary material as a result of the close-in giant planets scattering inner rocky planets into the star as they migrated to their present-day locations. Using high-resolution, high signal-to-noise echelle spectra, for both stars in each system we derive the chemical abundances ([X/H]) of 15 elements covering a range of condensation temperatures (Tc). For stars in our sample with approximately solar metallicity, the refractory elements (Tc > 900 K) show a positive correlation between [X/H] and Tc. However, for stars with super-solar metallicities, the refractory elements show a slightly negative correlation between [X/H] and Tc. We interpret these results in the context of numerical simulations of giant planet migration that predict the accretion of hydrogen-depleted rocky material by the host star. We demonstrate that a simple model for a solar-metallicity star accreting material with Earth-like composition predicts a positive correlation between [X/H] and Tc, while for a supersolar-metallicity star the model predicts a negative correlation. The stark contrast between the predicted correlations for solar-metallicity and supersolar-metallicity stars may indicate that extracting any chemical signature of rocky planetary accretion is particularly challenging for very metal-rich stars.

Henry Ngo (Caltech):   Companion-driven Dynamics: Trends in Stellar Companion Fraction and Giant Exoplanet Orbital Properties

Many of the stars in the solar neighborhood are part of multiple star systems, which may affect the formation and subsequent orbital evolution of the planets in these systems. It has been suggested that such interactions might be responsible for hot Jupiter migration and/or the spin-orbit misalignments observed in many hot Jupiter systems. In order to investigate whether stellar companions can explain the present-day properties of the population of hot Jupiters, we carried out a high contrast imaging survey at Keck to determine the frequency of stellar companions around giant planet host stars. Here we present results from surveys of two giant planet populations. First, we present a new expanded sample of 80 stars with transiting hot Jupiters, which confirms and expands on the results from our previous survey. We find that the binary fraction of hot Jupiter host stars is enhanced by approximately a factor of two compared to that of field stars, suggesting that stellar companions may play an important role in these systems. We also find no correlation between misaligned hot Jupiters and the presence of a stellar companion. Second, we present results from a new imaging survey of 146 RV-detected giant planet host stars, including systems with planets at a range of orbital separations, which allow us to search for correlations between stellar multiplicity and the orbital parameters of the inner planets.

David Armstrong (U Warwick):   The Abundance of Circumbinary Exoplanets

Circumbinary planets, planets orbiting around binary stars, represent a new angle of information on planet formation theories, showing us how the different processes that form a planet react to the torque of a central host binary. I will present recently published observational constraints on the occurrence rates and orbital element distributions of circumbinary planets. This work utilises the Kepler dataset of ~2000 eclipsing binaries, along with an independently developed tailored search algorithm, to debias the dataset and find the underlying frequency of these planets. We discover that circumbinary planets have a similar occurrence rate to planets around single stars, but only if they are preferentially coplanar with their host binary. If they are more misaligned, they must be significantly more common. This effect is strong enough that following a reductio ad absurdum argument, we confirm the coplanar preference for these planets. Along with these results, we confirm the previously noted tendency for circumbinary planets to not be found around the closest (P(binary) < ~7 days) host binaries. This last result may be a marker of the binary star formation process.
Contributing Teams: D. J. Armstrong (University of Warwick, Department of Physics; ARC, Queens University Belfast); H. P. Osborn, D. J. A. Brown, F. Faedi, Y. Gómez Maqueo Chew, D. Pollacco (University of Warwick, Department of Physics); D. V. Martin, S. Udry (Observatoire de Genève, Université de Genève)

Diego Munoz (Cornell):   Survival of Planets around Shrinking Stellar Binaries

The discovery of transiting circumbinary planets by the Kepler mission suggests that planets can form efficiently around binary stars. None of the stellar binaries currently known to host planets has a period shorter than 7 days, despite the large number of eclipsing binaries found in the Kepler target list with periods shorter than a few days. These compact binaries are believed to have evolved from wider orbits into their current configurations via the so-called Lidov-Kozai migration mechanism, in which gravitational perturbations from a distant tertiary companion induce large-amplitude eccentricity oscillations in the binary, followed by orbital decay and circularization due to tidal dissipation in the stars. We present new results (PNAS 112, 30, p 9264) on the orbital evolution of planets around binaries undergoing orbital decay by this "LK+tide" mechanism. From secular and N-body calculations, we show how planets may survive and become misaligned from their host binary, or may develop erratic behavior in eccentricity, resulting in their consumption by the stars or ejection from the system as the binary decays. Either outcome can explain these planets' elusiveness to detection. Our results suggest that circumbinary planets around compact binaries could still exist, and we offer specific predictions as to what their orbital configurations should be like.
Contributing Teams: Diego J. Munoz Dong Lai

6:00 PM: Banquet (Marriott Beach Luau)


8:30 AM — Habitability and Biosignatures    [Chair: Lisa Kaltenegger]

Sara Seager (MIT):   Towards a List of Molecules as Potential Biosignature Gases for the Search for Life on Exoplanets

Thousands of exoplanets are known to orbit nearby stars. Plans for the next generation of space-based and ground-based telescopes are fueling the anticipation that a precious few habitable planets can be identified in the coming decade. Even more highly anticipated is the chance to find signs of life on these habitable planets by way of biosignature gases. But which gases should we search for? We expand on the search of possible biosignature gases and go beyond those studied so far, which include O2, O3, N2O, and CH4, as well as secondary metabolites: methanethiol (CH3SH), dimethyl sulfide ((CH3)2S), methyl chloride (CH3Cl), and carbonyl sulfide (CSO). We present the results of a project to map the chemical space of life’s metabolic products. We have constructed a systematic survey of all possible stable volatile molecules (up to N=6 non-H atoms), and identified those made by life on Earth. Some (such as methyl chloride) are made by Earth life in sufficiently substantial quantities to be candidate biosignatures in an Earth-like exoplanet’s atmosphere; some, such as stibine (SbH3), are produced only in trace amounts. Some entire categories of molecules are not made by Earth life (such as the silanes); these and other absences from the list of biogenic volatiles point to functional patterns in biochemical space. Such patterns may be different for different biochemistry, and so we cannot rule out any small, stable molecule as a candidate biosignature gas. Our goal is for the community to use the list to study the chemicals that might be potential biosignature gases on exoplanets with atmospheres and surface environments different from Earth’s.

Pilar Montañés-Rodriguez (Canarias):   The Search for Life in our Galaxy: Using the Solar System Planets as Benchmarks

Over the past decades a large diversity in planetary systems, accompanied by a large diversity of planetary natures, have been discovered. Nevertheless, despite probable surprises, our knowledge of the solar system planets will be our guidance in the interpretation of the physical properties of extrasolar planet atmospheres. Thus, the solar system offers a unique playground to determine the best observables for such planet characterization. In the past few years, our group has performed observations aimed at retrieving the reflection and transmission spectrum of some of the solar systems planets. These observations include the transmission spectrum of Earth (via a lunar eclipse), the transmission spectrum of Venus (via the transit of Venus in 2012 observed from SOFI) and the transmission spectrum of Jupiter (via a Ganymedes eclipse). Together they have revealed a wealth of new information, such as the detectability of dimer bands (usable as tracers of atmospheric pressure) in earth-like planets, or the signatures of aerosols, hazes and metallic layers in giant planets. Here I am planning to offer a review of the observational setup of these observations, and what they have revealed about Earth, Venus and Jupiter in the context of the search for life in our galaxy
Contributing Teams: Instituto de Astrofisica de Canarias

Ravi Kopparapu (NASA Goddard):   Determining the Inner Edge of the Habitable Zone around M and Late K-Stars Using 3-D Climate Models

We present preliminary results for the inner edge of the habitable zone (HZ) around M and late K-stars, calculated from state of the art 3-D global climate models, the NCAR Community Atmosphere Model and Flexible Modeling System (FMS) developed by the Geophysical Fluid Dynamics. Both 1-D and 3-D models show that, for a water-rich planet, as the surface temperature increases due to increased stellar radiation, water vapor becomes a significant fraction of the atmosphere. M- and late K-stars have their peak flux in the near-infrared, where water is a strong absorber. Our models have been updated with a new radiation scheme and with H2O absorption coefficients derived from the most recent line-by-line databases (HITRAN2012 and HITEMP2010). These updates will most likely result in moving the inner edge of the HZ around M and late-K stars further away from the star than previous estimates. The initial targets for survey missions such as K2 and the Transiting Exoplanet Survey Satellite (TESS) will likely be planets near the inner edge of the HZ due to the increased signal-to-noise ratio that results from their proximity to their host star. The James Webb Space Telescope (JWST) may be capable of probing the atmospheric composition of terrestrial planets around a nearby M-dwarf. Thus, determining the most accurate inner edge of the HZ around M-dwarf stars is crucial for selecting target candidates for atmospheric characterization and to identify potential biomarkers.

Daniel Kitzmann (U Bern):   The Unstable CO2 Feedback Cycle on Ocean Planets

Ocean planets are volatile rich planets, not present in our Solar System, which are dominated by deep, global oceans. Theoretical considerations and planet formation modeling studies suggest that extrasolar ocean planets should be a very common type of planet. One might therefore expect that low-mass ocean planets would be ideal candidates when searching for habitable exoplanets, since water is considered to be an essential requirement for life. However, a very large global ocean can also strongly influence the climate. The high pressure at the oceans bottom results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. In our study we, therefore, focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a fundamental quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree. In contrast to the stabilising carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle on ocean planets is positive and has strong destabilising effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle is severely limiting the potential habitability of ocean planets.

Sarah Rugheimer (St Andrews):   Characterizing Pale Blue Dots Around FGKM Stars

Exoplanet characterization of small rocky worlds will be a main focus in the coming decades. For future telescopes like JWST and UVOIR/HDST, an exoplanet’s host star will influence our ability to detect and interpret spectral features, including biosignatures. We present a complete suit of stellar models and a grid of model atmospheres for Earth-like planets at equivalent stages of geological evolution in their HZ for stellar effective temperature from Teff = 2300K to 7000K, sampling the entire FGKM stellar type range. Since M dwarfs are simultaneously the most numerous in the universe, the most active, and the most likely stars to host terrestrial exoplanets, we focus in particular on the range of UV emission possible in each sub M spectral class. The UV emission from a planet's host star dominates the photochemistry and thus the resultant observable spectral features of the planet. Using the latest UV spectra obtained by HST and IUE we model the effect of stellar activity on Earth-like planets. We also model the amount of UV flux reaching the surface for Earth-like planets at various geological epochs ranging from a pre-biotic world through the rise of oxygen and for Earth-like planets orbiting FGKM stars at equivalent stages of evolution. When modeling the remotely detectable spectra of these planets we focus on the primary detectable atmospheric features that indicate habitability on Earth, namely: H2O, CO2, O3, CH4, N2O and CH3Cl. We model spectra of Earth-like planets orbiting our grid of FGKM stars in the VIS/NIR (0.4 – 4 μm) and the IR (5 – 20 μm) range as input for future missions and concepts like UVOIR/HDST and JWST.

Evgenya Shkolnik (Arizona State):   The High-Energy Radiation Environment of Planets around Low-Mass Stars

Low-mass stars are the dominant planet hosts averaging about one planet per star. Many of these planets orbit in the canonical habitable zone (HZ) of the star where, if other conditions allowed, liquid water may exist on the surface. A planet’s habitability, including atmospheric retention, is strongly dependent on the star’s ultraviolet (UV) emission, which chemically modifies, ionizes, and even erodes the atmosphere over time including the photodissociation of important diagnostic molecules, e.g. H2O, CH4, and CO2. The UV spectral slope of a low-mass star can enhance atmospheric lifetimes, and increase the detectability of biologically generated gases. But, a different slope may lead to the formation of abiotic oxygen and ozone producing a false-positive biosignature for oxygenic photosynthesis. Realistic constraints on the incident UV flux over a planet’s lifetime are necessary to explore the cumulative effects on the evolution, composition, and fate of a HZ planetary atmosphere. NASA’s Galaxy Evolution Explorer (GALEX) provides a unique data set with which to study the broadband UV emission from many hundreds of M dwarfs. The GALEX satellite has imaged nearly 3/4 of the sky simultaneously in two UV bands: near-UV (NUV; 175–275 nm) and far-UV (FUV; 135–175 nm). With these data these, we are able to calculate the mean UV emission and its level of variability at these wavelengths over critical planet formation and evolution time scales to better understand the probable conditions in HZ planetary atmospheres. In the near future, dedicated CubeSats (miniaturized satellites for space research) to monitor M dwarf hosts of transiting exoplanets will provide the best opportunity to measure their UV variability, constrain the probabilities of detecting habitable (and inhabited) planets, and provide the correct context within which to interpret IR transmission and emission spectroscopy of transiting exoplanets.

10 AM — Coffee Break

10:30 AM — Population Statistics and Mass-Radius Relations    [Chair: Diana Valencia]

Chris Burke (SETI Institute):   Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample

I discuss latest results in measuring terrestrial planet occurrence rates using the planet candidates discovered by the Kepler pipeline. For the first time an accurate model for the Kepler pipeline sensitivity to transiting planets is publicly available. My new analysis finds higher planet occurrence rates and a steeper increase in planet occurrence rates toward small planets than previously believed. In addition, I identify the leading sources of systematics that remain impacting Kepler planet occurrence rate determinations, and approaches for minimizing their impact in future studies. This work also sharpens our understanding on the dependence of planet occurrence rates on stellar effective temperature with implications for understanding the planet formation process.
Contributing Teams: Kepler Project

Erik Petigura (Caltech):   Prevalence and Properties of Planets from Kepler and K2

Discoveries from the prime Kepler mission demonstrated that small planets (< 3 Earth-radii) are common outcomes of planet formation around G, K, and M stars. While Kepler detected many such planets, all but a handful orbit faint, distant stars, which are not amenable to precise follow up measurements. NASA's K2 mission has the potential to increase the number of known small, transiting planets around bright stars by an order of magnitude. I will present the latest results from my team's efforts to detect, confirm, and characterize planets using the K2 mission. I will highlight some of the progress and remaining challenges involved with generating denoised K2 photometry and with detecting planets in the presence of severe instrument systematics. Among our recent discoveries are the K2-3 and K2-21 planetary systems: M dwarfs hosting multiple transiting Earth-size planets with low equilibrium temperatures. These systems offer a convenient laboratory for studying the bulk composition and atmospheric properties of small planets receiving low levels of stellar irradiation, where processes such as mass loss by photo-evaporation could play a weaker role.
Contributing Teams: California Planet Search, California/Arizona/Hawaii K2 Team

Courtney Dressing (Caltech):   The Occurrence Rate and Composition of Small Planets Orbiting Small Stars

I will describe two investigations of the galactic abundance and properties of small planets orbiting small stars based on data from the Kepler and K2 missions. First, we constrained the planet occurrence rate for early M dwarfs by searching the full four-year Kepler data set using our own planet detection pipeline. We measured a cumulative planet occurrence rate of 2.5 +/- 0.2 planets per M dwarf with periods of 0.5-200 days and planet radii of 1-4 Earth radii. Within a conservative habitable zone based on the moist greenhouse inner limit and maximum greenhouse outer limit, we estimated an occurrence rate of 0.16 (+0.17/-0.07) Earth-size planets and 0.12 (+0.10/-0.05) super-Earths per M dwarf HZ. Second, I will report on ongoing efforts to characterize the population of small planet candidates detected by the K2 mission and discuss how the properties of the small planets orbiting late M dwarfs and K dwarfs compare to those orbiting early M dwarfs. We are gathering near-infrared spectra of the host stars and employing empirical relations (benchmarked to interferometry) to determine their metallicities, temperatures, and radii. The improved stellar properties permit us to constrain better the radii and insolation flux of the planet candidates and search for correlations between stellar and planetary properties. We are also conducting an intensive radial velocity campaign with HARPS-N and HIRES to estimate the masses and densities of the subset of small planet candidates orbiting the brightest low-mass host stars.
Contributing Teams: The HARPS-N Consortium & The Hawaii/California/Arizona/Indiana K2 Follow-up Collaboration

Angie Wolfgang (Penn State):   A Probabilistic Mass-Radius Relationship for Sub-Neptune-Sized Planets: Implications for Missions Post-Kepler

The Kepler Mission has discovered thousands of planets with radii between 1 and 4 R_Earth, paving the way for the first statistical studies of the dynamics, formation, and evolution of planets in a size range where there are no Solar System analogs. Masses are an important physical property for these theoretical studies, and yet the vast majority of Kepler planet candidates do not have theirs measured. Therefore, a key practical concern is how to most accurately map a measured sub-Neptune radius to a mass estimate given the existing observations. This issue is also highly relevant to devising the most efficient follow-up programs of future transiting exoplanet detection missions such as TESS. Here we present a probabilistic mass-radius relationship (M-R relation) evaluated within a hierarchical Bayesian framework, which both accounts for the anticipated intrinsic dispersion in these planets' compositions and quantifies the uncertainties on the M-R relation parameters. Assuming that the M-R relation can be described as a power law with a dispersion that is constant and normally distributed, we find that M/M_Earth = 2.7 (R/R_Earth)^1.3 and a scatter in mass of 1.9 M_Earth is the "best-fit" probabilistic M-R relation for the sample of RV-measured transiting sub-Neptunes (R_pl < 4 R_Earth; Wolfgang, Rogers, & Ford, in review). The probabilistic nature of this M-R relation has several advantages: not only does its use automatically account for a significant source of uncertainty in the comparison between planet formation theory and observation, but it can predict the yield of future transit missions' follow-up programs under the observed range of planet compositions at a given radius. We demonstrate the latter with TESS as a case study, building on Sullivan et al. 2015 to provide the RV semi-amplitude distribution predicted by this more general M-R relation and a more detailed treatment of the underlying planet population as derived from Kepler. The uncertainties in the predicted K distribution, which are driven by our derived spread of masses at a given radius, provide an additional consideration for choosing the best RV follow-up target selection strategy.

Megan Shabram (Penn State):   The Mass-Radius-Eccentricity Distribution of Near-Resonant Transiting Exoplanet Pairs Detected by Kepler

We characterize the mass-radius-eccentricity distribution of transiting planets near first-order mean motion resonances using Transit Timing Variation (TTV) observations from NASA's Kepler mission. Kepler's precise measurements of transit times (Mazeh et al. 2014; Rowe et al. 2015) constrain the planet-star mass ratio, eccentricity and pericenter directions for hundreds of planets. Strongly-interacting planetary systems allow TTVs to provide precise measurements of masses and orbital eccentricities separately (e.g., Kepler-36, Carter et al. 2012). In addition to these precisely characterized planetary systems, there are several systems harboring at least two planets near a mean motion resonance (MMR) for which TTVs provide a joint constraint on planet masses, eccentricities and pericenter directions (Hadden et al. 2015). Unfortunately, a near degeneracy between these parameters leads to a posterior probability density with highly correlated uncertainties. Nevertheless, the population encodes valuable information about the distribution of planet masses, orbital eccentricities and the planet mass-radius relationship. We characterize the distribution of masses and eccentricities for near-resonant transiting planets by combining a hierarchical Bayesian model with an analytic model for the TTV signatures of near-resonant planet pairs (Lithwick & Wu 2012). By developing a rigorous statistical framework for analyzing the TTV signatures of a population of planetary systems, we significantly improve upon previous analyses. For example, our analysis includes transit timing measurements of near-resonant transiting planet pairs regardless of whether there is a significant detection of TTVs, thereby avoiding biases due to only including TTV detections.

Daisuke Suzuki (Notre Dame):   Discovery of a Break in the Exoplanet Mass-Ratio Function beyond the Snow Line

We present the discovery of a break in the exoplanet mass ratio function beyond the snow line from the statistical analysis of microlensing survey data. We find a break and possible peak of the mass ratio function at q ~ 1.e-4. This corresponds to a Neptune mass for a typical 0.5 solar mass host star. Six years of MOA survey data are used to measure the planet frequency as a function of the planet/star mass ratio and separation. The MOA sample includes 1472 well characterized microlensing events, including 22 planetary events and 1 probable planetary event. We calculate the detection efficiency for each event and employ a Bayesian analysis to deal with ambiguities. The measured planet frequency with the MOA data is somewhat lower, but consistent with, previous microlensing results. The break of the mass ratio function is also confirmed with the full microlensing sample using 30 planets. This study implies that Neptunes and failed Jupiter cores are the most common type of planets beyond the snow line. The method we have developed to determine the exoplanet frequency from microlensing survey data can be applied to future exoplanet microlensing surveys, like WFIRST, Euclid, and KMTNet that are expected to dominate the exoplanet microlensing field in the coming decades.

Subo Dong (Peking):    Kepler Planet Census Aided by LAMOST

The lack of spectroscopic stellar parameters for the majority of Kepler target stars present a major limitation to Kepler planet statistics. An ongoing spectroscopic survey of the Kepler field has been conducted by the LAMOST telescope in China, and accurate stellar parameters have already been obtained for tens of thousands of Kepler targets. I discuss studies using the LAMOST data that lead to new insights into our understanding of Kepler planet distributions.

Lunch Break

2:00 PM — Planets around Evolved Stars and Compact Remnants    [Chair: Steinn Sigurdsson]

Andreas Quirrenbach (Landessternwarte Heidelberg):   Planets around Giant Stars: Results from the Lick Survey

We present results from a radial-velocity survey of 373 giant stars at Lick Observatory, which started in 1999. We have detected planets around 15 of these stars; an additional 20 stars host planet candidates. Companions with up to 25 Jupiter masses are rather commonly found around stars with about 2 Solar masses. The frequency of detected planetary companions appears to increase with metallicity. No planets or planet candidates are found around stars with more than 2.7 Solar masses, although our sample contains 113 such stars. We conclude that the occurrence rate of giant planets as a function of Stellar mass peaks around 2 Solar masses. This has important consequences for our understanding of giant planet formation. The stars 91 Aqr and tau Gem have companions with orbits that are among those with the lowest eccentricities of all known exoplanets, perhaps due to tidal circularization during the RGB phase. If confirmed, this would be the first evidence of planetary orbits modified through stellar evolution. We have discovered several multiple systems in our sample. An extensive dynamical analysis of the eta Cet system indicates that it contains two massive planets in a 2:1 orbital resonance. The star nu Oph is orbited by two brown dwarf companions in a 6:1 resonance. It is likely that they arrived in this resonance through migration in a circumstellar disk, arguing strongly that objects with more than 20 Jupiter masses can be formed in disks around Herbig Ae stars.

Bryce Croll (Boston U):   Multiwavelength Transit Observations of the Candidate Disintegrating Planetesimals Orbiting a White Dwarf

At the time of writing of this abstract, an intriguing white dwarf system is shortly to be announced that is believed to be orbited by up to six or more disintegrating, planetesimals in short-period orbits. We report a wealth of multiwavelength, ground-based photometry of this system, and detect multiple transits of up to 30% of the stellar flux. The transits display the variable transit depths and transit profiles featuring longer egresses than ingresses that we have come to associate with disintegrating planets/planetesimals. Our photometry confirms that this white dwarf is indeed being orbited by multiple planetesimals, with at least one object, and likely more, having orbital periods of ∼4.5 hours; we are unable to confirm the specific periods that have been reported, thus bringing into question the long-term stability of the planetesimals' orbits. Lastly, our multiwavelength transit photometry allows us to place a limit on the particle size in the cometary tails trailing these planetesimals, helping to determine the mechanism (collisions, tidal disruption, a Parker wind, etc.) that has led to both the cometary tails and the arrival of these planetesimals in such short period orbits.

Boris Gaensicke (U Warwick):   The Final Fate of Planetary Systems

The discovery of the first extra-solar planet around a main-sequence star in 1995 has changed the way we think about the Universe: our solar system is not unique. Twenty years later, we know that planetary systems are ubiquitous, orbit stars spanning a wide range in mass, and form in an astonishing variety of architectures. Yet, one fascinating aspect of planetary systems has received relatively little attention so far: their ultimate fate. Most planet hosts will eventually evolve into white dwarfs, Earth-sized stellar embers, and the outer parts of their planetary systems (in the solar system, Mars and beyond) can survive largely intact for billions of years. While scattered and tidally disrupted planetesimals are directly detected at a small number of white dwarfs in the form infrared excess, the most powerful probe for detecting evolved planetary systems is metal pollution of the otherwise pristine H/He atmospheres. I will present the results of a multi-cycle HST survey that has obtained COS observations of 136 white dwarfs. These ultraviolet spectra are exquisitely sensitive to the presence of metals contaminating the white atmosphere. Our sophisticated model atmosphere analysis demonstrates that at least 27% of all targets are currently accreting planetary debris, and an additional 29% have very likely done so in the past. These numbers suggest that planet formation around A-stars (the dominant progenitors of today's white dwarf population) is similarly efficient as around FGK stars. In addition to post-main sequence planetary system demographics, spectroscopy of the debris-polluted white dwarf atmospheres provides a direct window into the bulk composition of exo-planetesimals, analogous to the way we use of meteorites to determine solar-system abundances. Our ultraviolet spectroscopy is particularly sensitive to the detection of Si, a dominant rock-forming species, and we identify up to ten additional volatile and refractory elements in the most strongly contaminated white dwarfs. The derived bulk abundances unambiguously demonstrate the predominantly rocky nature of the accreted material, with two exceptions where we detect volatile-rich debris. The relative abundance ratios suggest a wide range of parent bodies, including both primitive asteroids and fragments from differentiated planetesimals. The growing number of detailed debris abundances can provide important observational constraints on planet formation models.

Jay Farihi (UCL):   Water Detected in the Terrestrial Zone of Extreme Solar Systems

Life as we know it requires water in contact with a rocky planetary surface. In the Solar System, water and other volatiles must have been delivered to a dry Earth from planetesimals, where asteroids in the outer main belt and Jupiter-Saturn region are excellent candidates. The first extrasolar analog of these rocky and water-rich planetesimals was reported between ESS II and III (Farihi et al. 2013, Science, 342, 218), and there is now evidence for additional examples. These results imply an underlying population of large, extrasolar planetesimals formed near a snow line, and suggesting a common mechanism for water delivery to habitable exoplanets. I will present Hubble, Spitzer, and ground-based data that demonstrate the confirmed and likely water-rich nature of exo-asteroids identified in a growing number of white dwarf planetary systems. These extreme solar systems formed and evolved around A-type (and similar) stars -- now firmly retired -- and the asteroid debris now orbits and pollutes the white dwarf with heavy elements, including oxygen in excess of that expected for oxide minerals. The abundance patterns are also carbon-poor, indicating the parent bodies were not icy planetesimals analogous to comets, but instead similar in overall composition to asteroids in the outer main belt. Importantly, these remnant exoplanetary systems imply architectures similar to the Solar System, where a giant planet exterior to a snow line perturbs rocky asteroids on the interior. Thus, they appear to share basic characteristics with HR 8799, Vega, Fomalhaut, and epsilon Eridani where two disks of debris are separated by giant planet(s), with one belt near the snow line. If such archictectures are as common as implied by polluted white dwarfs, then at least 30% of 1.2-3.0 Msun stars have both the tools and ingredentients for water delivery in their terrestrial planet zones.

Dimitri Veras (U Warwick):   Planetary Systems through all Stages of Stellar Evolution

We know that planetary systems around white dwarfs are just as common as those around main sequence stars. However, observations reveal significant gaps in our understanding about how planets, asteroids, comets and pebbles undergo physical and orbital changes as their parent stars evolve off of the main sequence. We have performed full-lifetime (14 Gyr) numerical simulations of multi-planet systems across all phases of stellar evolution, incorporating realistic profiles for stellar mass loss and stellar radius variability, and including test particles and wide binary stellar companions. We demonstrate that closely-packed planetary systems can remain stable throughout the main sequence and for many Gyr during the white dwarf phase before unpacking and triggering scattering events. These events may generate an ever-changing dynamical architecture around the white dwarfs, and perturb planets onto orbits which can be detectable by transit photometry.

Alex Wolszczan (Penn State University):   The Pulsar Planets: Old Story - New Results

The Pulsar Planets: Old Story - New Results

3:30 PM - Coffee Break

4:00 PM — TESS and Other Future Missions    [Chair: Josh Winn]

George Ricker (MIT):   The Transiting Exoplanet Survey Satellite (TESS): Discovering New Earths and Super-Earths in the Solar Neighborhood

The Transiting Exoplanet Survey Satellite (TESS) will discover thousands of exoplanets in orbit around the brightest stars in the sky. In its two-year prime survey mission, TESS will monitor more than 200,000 bright stars in the solar neighborhood for temporary drops in brightness caused by planetary transits. This first-ever spaceborne all-sky transit survey will identify planets ranging from Earth-sized to gas giants, around a wide range of stellar types and orbital distances. TESS stars will typically be 30-100 times brighter than those surveyed by the Kepler satellite; thus, TESS planets will be far easier to characterize with follow-up observations. For the first time it will be possible to study the masses, sizes, densities, orbits, and atmospheres of a large cohort of small planets, including a sample of rocky worlds in the habitable zones of their host stars. An additional data product from the TESS mission will be full frame images (FFI) with a cadence of 30 minutes or less. These FFI will provide precise photometric information for every object within the 2300 square degree instantaneous field of view of the TESS cameras. These objects will include more than 1 million stars and bright galaxies observed during sessions of several weeks. In total, more than 30 million objects brighter than I=16 will be precisely photometered during the two-year prime mission. In principle, the lunar-resonant TESS orbit could provide opportunities for an extended mission lasting more than a decade, with data rates in excess of 100 Mbits/s. An extended survey by TESS of regions surrounding the North and South Ecliptic Poles will provide prime exoplanet targets for characterization with the James Webb Space Telescope (JWST), as well as other large ground-based and space-based telescopes of the future. TESS will issue data releases every 4 months, inviting immediate community-wide efforts to study the new planets, as well as commensal survey candidates from the FFI. A NASA Guest Investigator program is planned for TESS. The TESS legacy will be a catalog of the nearest and brightest main-sequence stars hosting transiting exoplanets, which should endure as the most favorable targets for detailed future investigations. TESS is targeted for launch in 2017 as a NASA Astrophysics Explorer mission.
Contributing Teams: TESS Science Team

David Latham (Harvard-Smithsonian CfA):   TESS Science and Community Involvement

Much of the scientific work in support of NASA’s TESS mission will be carried out by working groups, composed of members of the TESS Science team and experts from the community. For example, the goal of measuring masses for 50 planets smaller than 4 Earth radii will require extensive efforts by the TESS Follow-up Observing Program (TFOP), both for spectroscopic and photometric reconnaissance observations and for very precise radial velocities needed to determine orbits and planetary masses. These efforts will be coordinated and in many cases carried out by members of the TFOP Working Group. Other key working groups include Simulations, Target Selection, Asteroseismology, Atmospheric Characterization, Habitability, and Non-Exoplanet Science. A second opportunity for community involvement will be the Guest Investigator program run out of the Goddard Space Flight Center. The plan is for annual calls for proposals to do science other than the primary mission science, with the first call about a year before launch. This program will build on the experience of the highly successful Guest Observer programs for the Kepler and K2 missions.

Tiago Campante (U Birmingham):   Asteroseismology of Exoplanet-Host Stars in the TESS Era

New insights on stellar evolution and stellar interiors physics are being made possible by asteroseismology, the study of stars by the observation of their natural, resonant oscillations. Throughout the duration of the Kepler mission, asteroseismology has also played an important role in the characterization of host stars and their planetary systems. Examples include the precise estimation of the fundamental properties of stellar hosts, the obliquity determination of planetary systems, or the orbital eccentricity determination via asterodensity profiling. The Transiting Exoplanet Survey Satellite (TESS) will perform a wide-field survey for planets that transit bright host stars. Its excellent photometric precision and long intervals of uninterrupted observations will enable asteroseismology of solar-type stars and their evolved counterparts. Based on existing all-sky simulations of the stellar and planetary populations, we investigate the asteroseismic yield of the mission, placing particular emphasis on the yield of exoplanet-host stars for which we expect to detect solar-like oscillations. This is done both for the cohort of target stars (observed at a 2-min cadence), which will mainly involve low-mass main-sequence hosts, as well as for the cohort of “full-frame image” stars (observed at a 30-min cadence). The latter cohort offers the exciting prospect of conducting asteroseismology on a significant number of evolved hosts. Also, the brightest solar-type hosts with asteroseismology will become some of the best characterized planetary systems known to date. Finally, we discuss the impact of the detected oscillations on the accuracy/precision of the derived properties of the host stars and their planetary systems.

Christopher Broeg (U Bern):   The CHEOPS Mission

The CHaracterising ExOPlanet Satellite (CHEOPS) is a joint ESA-Switzerland space mission dedicated to search for exoplanet transits by means of ultra-high precision photometry. It is expected to be launch-ready at the end of 2017. CHEOPS will be the first space observatory dedicated to search for transits on bright stars already known to host planets. It will have access to more than 70% of the sky. This will provide the unique capability of determining accurate radii for planets for which the mass has already been estimated from ground-based radial velocity surveys and for new planets discovered by the next generation ground-based transits surveys (Neptune-size and smaller). The measurement of the radius of a planet from its transit combined with the determination of its mass through radial velocity techniques gives the bulk density of the planet, which provides direct insights into the structure and/or composition of the body. In order to meet the scientific objectives, a number of requirements have been derived that drive the design of CHEOPS. For the detection of Earth and super-Earth planets orbiting G5 dwarf stars with V-band magnitudes in the range 6 ≤ V ≤ 9 mag, a photometric precision of 20 ppm in 6 hours of integration time must be reached. This time corresponds to the transit duration of a planet with a revolution period of 50 days. In the case of Neptune-size planets orbiting K-type dwarf with magnitudes as faint as V=12 mag, a photometric precision of 85 ppm in 3 hours of integration time must be reached. To achieve this performance, the CHEOPS mission payload consists of only one instrument, a space telescope of 30 cm clear aperture, which has a single CCD focal plane detector. CHEOPS will be inserted in a low Earth orbit and the total duration of the CHEOPS mission is 3.5 years (goal: 5 years). The presentation will describe the current payload and mission design of CHEOPS, give the development status, and show the expected performances.
Contributing Teams: The CHEOPS Team http://cheops.unibe.ch

Nicholas Walton (Cambridge):   Gaia, PLATO and WEAVE: a Powerful Combination for Exoplanet Characterization

This presentation will describe the powerful linkages between the Gaia and PLATO missions and the potential impact of the WHT’s WEAVE multi-object spectrograph in the study of exoplanet populations. ESA’s Gaia mission commenced its nominal operations phase in July 2014. Its first data release is expected summer 2016. Over the course of its (at least) five year mission, it will discover, via their astrometric signatures, upwards of 20,000 massive Jupiter sized long period planets at distances out to several hundred parsecs around all star types. In addition Gaia will discover a significant number of short period hot Jupiters around M stars. This presentation will discuss the form and content of the first Gaia Data Release. The ESA PLATO mission, planned to launch in 2024, will photometrically observe a million host stars, and will detect, via the transit technique, planets down to Earth masses. PLATO will observe two fields of over 2,000 square degrees for 2 to 3 years each. At least one of these will be in the northern hemisphere. where WEAVE (a new multi object high resolution spectrograph currently under construction for the 4.2m William Herschel Telescope) will have the potential to provide detailed chemical characterisation of the host stars of the Gaia and PLATO exoplanet systems. This will enable insights into, for instance, metallicity of the host star correlations against both massive exoplanets (perhaps confirming current relationships), and lower mass exoplanets. We note how the rapid exploitation of such a potential WEAVE survey could be achieved, utilising the WEAVE processing systems being developed at the IoA, Cambridge, coupled with efficient interfaces to the Cambridge Gaia and PLATO data processing centres.
Contributing Teams: The description of the Gaia status and first Gaia Data Release will be presented for the Gaia Science Team.

Lison Malo (CFHT):   SPIRou — A Near-Infrared Spectropolarimeter at CFHT

SPIRou is a near-infrared spectropolarimeter and a high-precision velocimeter optimized for both the detection and characterization of terrestrial planets orbiting nearby low-mass stars, and the study of the impact of magnetic field on the star-planet formation. The spectrograph is designed to record the whole near-infrared spectrum simultaneously in either circular or linear polarization and to reach a RV precision of 1 m/s at a resolving power of 75,000. It will be use to carry out the "SPIRou Legacy Survey" targeting two science objectives (habitable terrestrial planet detection & magnetic field impact on star-planet formation) and is intended to provide the community with an extensive, homogenous, well characterized and high-quality data. SPIRou is expected to make a major breakthrough in the field of telluric planets in the habitable zone of cool stars. Once implemented at CFHT in 2017, SPIRou is expected to be used extensively by the astronomical community - supporting in particular space missions such as TESS, JWST and PLATO. In this presentation, I will focus on the impact of the SPIRou future observing programs in the field of exoplanets: 1) the radial-velocity survey, its target selection of cool dwarfs, strategy and expectations; 2) the follow-up characterization of transiting candidates; 3) the search for giant planets around very young stars; 4) the importance of spectropolarimetry to filter out the intrinsic jitter of target stars at the sub m/s level; 5) the anticipated role in preparing further exoplanet characterization missions.
Contributing Teams: SPIRou science team, SPIRou project office

5:30 PM - Conference ends

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