ElectroMagnetic follow-up observation for gravitational wave event with Subaru/HSC

speaker: Takayuki Ohgami

Gravitational wave (GW) astronomy was pioneered by the first detection of gravitational wave in 2015, and the first identification of electromagnetic counterpart of GW source opened a door of multimessenger astronomy. In Japan, J-GEM (Japanese Collaboration for Gravitational-Wave Electro-Magnetic Follow-up) is organized to perform immediate follow-up observations of GW with optical and near-infrared telescopes in Japan and overseas. Deepest and widest imaging capabilities of the Subaru telescope/Hyper Suprime-Cam (HSC) with an FoV of 1.8 deg^2 attract attention since more and more distant GW events and fainter EM emission in a larger survey volume as GW sensitivity improves are expected. The LIGO/Virgo began their 3rd observing run (O3) in April 2019, and they reported 56 events were detected. We conducted survey observation for three events, S190510g, S191216ap and S200224a with Subaru/HSC. In S190510g, we made the quick turnaround observation 1.7 hr after receiving the preliminary alert, which demonstrated early identification possible. In S200224ca, we made the deepest optical observation over 80% of the 90% credible localization. In this talk, we will report the observations, data analysis, and the candidates of optical counterpart of the GW events.