Speaker
Description
The detection of gravitational waves (GWs) from LIGO and Virgo interferometers opened a new era for multi-messenger observations especially with the coincident detection between GW events and gamma-ray burst (GRB) detection. The first GW event detected by LIGO on the $14^{th}$ September 2015 (Abbott et al. 2016) was a binary black hole merger (BBH) until August 2017 nine other mergers of black holes were detected during runs O1 and O2. Exceedingly the most interesting object for multi-messenger astronomy was the merger of binary neutron star (BNS) detected on $17^{th}$ August 2017 (Andreoni et al. 2017). The merger was detected in various electromagnetic waves and allowed to confirm the kilonova model (Metzger et al. 2010). This research started with the analysis of images recorded by the TAROT telescopes during runs O1 and O2 to detect new optical sources associated to black hole mergers; GW150914, GW170104 and GW170814. The analysis pipeline was developed to detect new sources by matching the image data with the Gaia catalog data release 1, the angular distance between objects in the image and in the catalog were used to define new sources. We then process the candidates to validate them as possible new unknown objects. Though several possible candidates were detected in the three gravitational wave source error boxes studied, none of them were confirmed as a viable counterpart. Even though none of optical transient had been detected but the limiting magnitude of the particular BBH event of $14^{th}$ August 2017 gave new constraints about the hypothetical link with gamma ray bursts (Noysena et al. 2019). Three GW events were observed with TAROT allowing us to constrain $\alpha < 10^{-5}$, the fraction of energy emitted by gravitational waves converted into optical light. An approximately 100% coverage of localization of GW170814 was observed at 0.6 days after GW triggering with no evidence of optical transient and 65% of 147 optical light curves of GRBs known redshift were excluded. The optical follow up of GW sources by TAROT and a new method to increase the efficiency of the detection pipeline are pioneering experiences forward to the next GW counterpart in the next observing run O4 of GW observatory, we could find more optical evidence from the GW merger events.
