IDEAS NRT Trainee Michael Zevin is a member of the LIGO Scientific Collaboration and studies how gravitational waves can help us learn about populations of compact objects. Gravitational waves observed by LIGO encode information about their massive-star progenitors, such as the environments they were born in, the intricacies of stellar evolution that persisted throughout their lives, the supernovae that marked their deaths.
In a recent publication, Zevin investigated black hole mergers that occur in dense stellar environments called globular clusters. Some of the mergers from these environments have a characteristic imprint in their gravitational-wave signal –residual eccentricity, or how elliptical their orbit is when LIGO observes them.
The training from DATA-SCI 401 was key to understanding how such parameters can be inferred from the raw gravitational-wave strain data. To quantify the rate and properties of these signals, Zevin performed a comprehensive set of scattering experiments, numerically evolving millions of encounters. Thanks to his IDEAS training, particularly through the DATA-SCI 421 class, Zevin statistically quantified how often these chaotic encounters led to a merger that showed signs of eccentricity. He found 5-10% of mergers from globular clusters should have residual eccentricity detectable by LIGO, and that at least 25% of these come from encounters involving 4 black hole. Observing an eccentric signal with LIGO will be a tell-tale sign of the environment it formed in, one of the key questions in gravitational-wave astrophysics.
DATA-SCI 401 and 421 are both courses developed by the IDEAS faculty, with the support of the IDEAS NRT Grant.