Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) logo

The centers of galaxies are complex environments whose properties are a result of the interactions between the massive black holes that reside there, vast clouds of gas, and dense populations of stars and stellar remnants.

Professor Rasio’s group studies numerical models of dense stellar environments such as nuclear star clusters.

Professor Larson’s group studies the interactions of single stars with massive black holes, a prospective LISA gravitational wave source class known as an EMRI (“extreme mass ratio inspiral”).

Professor Zadeh is an observer who studies stellar populations and physical processes in the Milky Way nucleus using observations across the electromagnetic spectrum.

Galaxies are often attended by a group of dense stellar clusters orbiting in a vast area around the galaxy. These globular clusters are comprised of hundreds of thousands to millions of stars, and are held together by their mutual gravitational attraction.

Professor Rasio’s group uses numerical modeling techniques to simulate the evolution of globular clusters over the history fo the Universe, and studies how the observational properties of these clusters are derived from their evolutionary history.

Professors Kalogera and Larson collaborate closely with the globular cluster simulation group, since the clusters are potentially the home to large populations of gravitational wave sources observable by both LIGO and LISA.

The close interaction of stars, stellar remnants, or combinations of both, will have dramatic consequences for the future evolution of the system and the long term properties of stellar populations. At CIERA these systems are studied both theoretically and observationally.

Professor Kalogera’s and Larson’s groups both use population synthesis to study expected rates and properties of merger events, which are strong gravitational wave sources for LIGO when they merge, and for LISA at earlier times during their inspiral.

Professors Fong is an observer who studies explosive transients that can result from stellar mass mergers, such as gamma ray bursts.

A star’s life cycle can be dramatically influenced by co-evolution with a binary companion. Repeated episodes of tidal interactions, mass transfer, or common envelope evolution will change the physical properties of the individual stars as well as the orbit they share.

Professors Kalogera and Larson both use population synthesis techniques to understand how binary interactions influence the properties observed across the entire population of binaries. They also explore how gravitational wave observations with LIGO and LISA can be used to elucidate the complex interaction history of binaries.