Special Astronomy & Astrophysics Seminar: Electromagnetic Counterparts to Gravitational Waves

Abstract:

Direct detection of gravitational waves (GWs) is on the horizon, with the most promising sources being the mergers of two neutron stars (NS-NS) or a black hole and a neutron star (BH-NS). Maximizing the scientific return of this new window into the universe requires identifying a coincident electromagnetic (EM) counterpart. One probable EM counterpart is a short gamma-ray burst (GRB) but the emission is highly collimated. Isotropic EM emissions are also suggested by the general relativistic simulation results that the compact binary mergers eject substantial material in every direction, and may have been already observed as a macronova associated with the short GRB 130603B. We will first discuss the mass ejection mechanisms, such as anisotropic ejection from BH-NS and ultra-relativistic ejection from the NS-NS merger shock. We will then move on to the energy sources, such as radioactivity of r-process elements synthesized in the ejecta, the central engine activity (for heating or scattering), and interaction with the interstellar medium. We also present new pictures of short GRBs, such as the jet collimation by the merger ejecta, and a BH engine producing long-lasting plateau emission up to ~10,000 s via Blandford-Znajek process with ordinary NS magnetic field of 10^{12} G. If time permits, we will touch on topics related to fast radio bursts, population III GRBs, IceCube neutrinos, and AMS-02 cosmic rays.

Seminar Organizer: Prof. Rennan Barkana