|Description||2017 Fall Physics Colloquium Series|
Michael Kesden, Ph.D.
Assistant Professor of Physics
University of Texas at Dallas
Constraining Binary Black-Hole Formation with Gravitational-Wave Observations
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On September 14, 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) observed gravitational waves (GWs) from the inspiral and merger of two stellar-mass black holes. LIGO observed GWs from two additional black-hole mergers, GW151226 and GW170104, during its first two observing runs (and potentially other as yet unpublished events). Classical black holes are simple objects, fully characterized by their mass and spin (astrophysical black holes have negligible electric charge). Binary black holes are on circular orbits by the time they emit GWs at frequencies observable by LIGO, so these systems are described by just 7 intrinsic parameters: the two masses, two spin magnitudes, and three angles specifying the spin directions with respect to the orbital angular momentum. This paucity of potentially observable parameters, some of which are poorly constrained by current observations, suggests that it may be difficult to discover the astrophysical origin of binary-black hole systems. There are two competing channels for binary black-hole formation: either the binary black holes evolve from binary stellar progenitors, or isolated black holes subsequently form binaries in dense stellar environments like globular clusters. In this talk, I will discuss how binary black-hole spins precess between formation and merger and argue that this precession allows observations of black-hole spins within the LIGO band to distinguish between the two channels of black-hole formation.
Dr. Anzhong Wang 254-710-2276