| Name: | Gaurav Waratkar |
| Affiliation: | Indian Institute of Technology Bombay |
| Conference ID : | ASI2023_202 |
| Title : | Sifting for electromagnetic counterparts to LIGO-Virgo Gravitational Wave triggers using AstroSat-CZTI |
| Authors : | Gaurav Waratkar (Indian Institute of Technology Bombay), Varun Bhalerao (Indian Institute of Technology Bombay), Aswin Suresh (Indian Institute of Technology Bombay), Dipankar Bhattacharya (Department of Physics Ashoka University & Inter-University Centre for Astronomy and Astrophysics India), Santosh Vadawale (Physical Research Laboratory). |
| Mode of Presentation: | Poster |
| Abstract Category : | Extragalactic Astronomy |
| Abstract : | The detection of a short GRB associated with GW1708017, along with other unprecedented multi-messenger follow-up observations, provided tremendous amounts of information on these evasive compact object mergers. This joint short GRB with GW detection established that binary neutron star mergers are indeed short GRB progenitors. Certain theoretical models allow for electromagnetic emission associated with binary black hole (BBH) mergers as well - indeed, Fermi-GBM had detected a weak signal temporally coincident with GW150914, the first BBH merger detected. By detecting over 500 GRBs since launch, the Cadmium Zinc Telluride Imager (20-200 keV) onboard AstroSat has been serving as an active all-sky Gamma-Ray Burst monitor. Here we present a review of our searches for GRBs coincident with gravitational wave (GW) triggers from the three LIGO-Virgo-KAGRA (LVK) Gravitational Wave Transient Catalogues (GWTC). Of the 90 LVK triggers, CZTI was in the South Atlantic Anomaly for 16 triggers. For the remaining 74 triggers, we undertook a systematic search for temporally coincident transients that was performed at different timescales and led to the detection of no X-ray counterparts. We evaluate the upper limits on maximum possible flux from the source in a 100s window around each trigger, consistent with the GW localisation of the event. Thanks to the high sensitivity of CZTI, these upper limits are highly competitive with those from other spacecraft. We use these upper limits to constrain the luminosity function of high-energy counterparts to the GW events. |
