Bright, Electromagnetic Counterparts to Supermassive Black Hole Mergers by Eric Coughlin

Room: 202/204 Physics Bldg.

Recent observations of a neutron star-neutron star merger verified -- in striking agreement with theoretical predictions -- that the gravitational waves emitted from such a merger are accompanied by an electromagnetic signature, which itself is bright from gamma-rays (the gamma-ray burst), to optical/UV (the kilonova), to radio (the afterglow). The corresponding electromagnetic signature from the inspiral of two supermassive black holes, the gravitational waves from which will be detectable in the upcoming era of space-based interferometry, is less clear. However, any potential signature and its detectability are likely determined by the distribution of gas around the black holes, and the dynamic response of that gas to the mass lost to gravitational waves during the final coalescence. In this talk, I will describe a mechanism responsible for generating a quasi-spherical, pressurized ``bubble'' of gas that enshrouds a supermassive black hole binary during the final years of its merger. I will show that the mass lost to gravitational waves initiates the formation of a pressure wave within this bubble, which steepens into a shock very near its surface. The breakout of this shock then powers a luminous, electromagnetic transient that can peak and fade on timescales of months to years. I will discuss these results in the context of the electromagnetic detectability of supermassive black hole binary mergers. 

 

Eric Coughlin, Columbia University

Host: Prof. Duncan Brown, Contact: Yudaisy Salomon Sargenton - phyadmin@syr.edu