Gravitational Wave Astronomy
The existence of gravitational waves (GWs) was predicted by Albert Einstein in his general theory of relativity in 1916. He showed that accelerating masses emit gravitational waves as the perturbations propagating on the fabric of space-time due to time-varying mass multipole moments of the source. GWs interact extremely weakly with the matter making them challenging to detect. The most promising known sources of GWs are the compact binary mergers (binary black holes, neutron star-black hole and binary neutron stars). Laser Interferometer Gravitational Wave Observatory (LIGO), at Livingston and Hanford, USA, made the first direct detection of GWs in 2015 opening a new window of astronomy to study the otherwise dark universe. These GWs were produced by the merger of two stellar-mass black holes in a binary system. This was the first ever direct confirmation of Einstein’s theory of general relativity (GR) in strong and relativistic regime of gravity. It was also the first observation of binary black hole (BBH) merger.
Since the first detection, LIGO in collaboration with Virgo interferometer has observed a plethora of events in various observing runs. This includes many BBH mergers, two binary neutron star (BNS) mergers, and two candidate neutron star-black hole (NSBH) mergers. Among the two BNS mergers, one was detected with its electromagnetic (EM) counterpart almost in the whole range of electromagnetic spectrum. This unprecedented joint gravitational and electromagnetic observation provided first direct evidence of a link between these BNS mergers and short γ-ray bursts and offered some hints on the formation of heavy elements in stars. It also provided new tools to study dense matter and cosmology. To realize the full scientific potential of such events, one would need to detect and identify the source location promptly. This will enable astronomers to point their telescopes to the source location before transient EM emission fades away. A significant part of my research focuses on improving these GW early-warning methods.