| Name: | Gaurav Waratkar |
| Affiliation: | Indian Institute of Technology Bombay |
| Conference ID : | ASI2024_334 |
| Title : | Sifting for electromagnetic counterparts to LIGO-Virgo-KAGRA Gravitational Wave triggers using AstroSat-CZTI |
| Authors : | Gaurav Waratkar 1, Varun Bhalerao 1, Dipankar Bhattacharya 2,3, Santosh Vadawale 4 |
| Authors Affiliation: | 1 Department of Physics, IIT Bombay, Powai, Mumbai - 400076, India
2 Inter-University Center for Astronomy and Astrophysics, Pune - 411007, India
3 Ashoka University, Department of Physics, Sonepat, Haryana - 131029, India
4 Physical Research Laboratory, Navrangpura, Ahmedabad - 380009, India |
| Mode of Presentation: | Poster |
| Abstract Category : | High Energy Phenomena, Fundamental Physics and Astronomy |
| Abstract : | The detection of a short Gamma-Ray Burst (GRB) associated with GW1708017, along with other unprecedented multi-messenger follow-up observations, 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 - which was supported by Fermi’s detection of a weak signal temporally coincident with GW150914, the first BBH merger detected. By detecting about 600 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 results from our searches for GRBs coincident with gravitational wave (GW) triggers from the LIGO-Virgo-KAGRA (LVK) Gravitational Wave Transient Catalogs (GWTCs). 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 localization 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. We discuss the probability of non-detections of BBH mergers at different luminosities to estimate the expected rates and the implications of such non-detections in the ongoing observing run O4 of LVK GW detectors.
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