Fundamental Stellar Astrophysics in the Gaia Era: A New Understanding of Local Stellar Populations
Mon, July 20, 2020
We begin with an overview of the precision stellar astrophysics enabled by the confluence of Gaia parallaxes with large-scale photometric and spectroscopic surveys. We then give examples of the new understanding of local Galactic structure that this has enabled, including in particular the detailed history of canonical star-forming regions, and the discovery of "stellar strings" reflecting the local conditions of recent star formation. We conclude with the example of a newly discovered, young, triple star system including an eclipsing binary, that provides prima facie evidence supporting the new "stellar strings" paradigm.
How do you form a binary black hole?
Mon, June 29, 2020
When an isolated binary black hole merges in the field of a galaxy, its gravitational-wave story is complete. But when black holes merge in a dense star cluster, their merger products can remain in the cluster, where they continue to participate in dynamical encounters, form binaries, and potentially merge again. In this talk I will describe the production of repeated mergers in globular clusters, and how the rate of mergers depends on the initial properties (e.g. spin) of black holes formed from stars. I will show how these "second-generation" black holes differ from black holes formed from stellar collapse, and how Advanced LIGO and Virgo can already distinguish these unique astrophysical populations.