Title: "Learning about compact objects using gravitational-wave and electromagnetic observations"
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 and its European partner Virgo observed GWs from four additional black-hole mergers during their first two observing runs, as well as GWs from a binary neutron-star merger (GW170817). Although astrophysical black holes are vacuum spacetime objects fully characterized by their masses and spins, neutron stars are composed of baryonic matter and can therefore produce electromagnetic emission as well. I will briefly summarize the LIGO observations of these sources along with electromagnetic observations of the binary neutron-star merger GW170817. These observations can be used to learn about both fundamental physics and the astrophysical origin of these systems. Comparing theoretical predictions of gravitational waveforms to observations tests general relativity in a variety of ways and also probes the equation of state of nuclear matter at high densities in the case of binary neutron-star mergers. Unlike neutron-stars, black holes may have large spins that imprint distinctive signatures on the GWs emitted prior to merger. Observation of these signatures in future high signal-to-noise events will allow us to determine whether binary black holes evolve from binary stellar progenitors, or isolated black holes subsequently form binaries in dense stellar environments like globular clusters.
*Refereshments will be served prior to the colloquium*