TITLE: GCN CIRCULAR NUMBER: 24115 SUBJECT: LIGO/Virgo S190412m: Fermi-LAT search for a high-energy gamma-ray counterpart DATE: 19/04/13 09:48:33 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (INFN & Politecnico Bari), M. Axelsson (KTH & Stockholm Univ.) and N. Omodei (Stanford Univ.) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on April 12, 2019, for possible high-energy (E>100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190412m. We define "instantaneous coverage" as the integral over the region of the LIGO probability map that is within the LAT field of view at a given a time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had instantaneous coverage of ~99% of the LIGO probability at the time of the trigger (T0 = 2019-04-12 05:30:44 UTC), and reached 100% cumulative coverage after ~7 ks. We performed a search for a transient counterpart within the 90% contour of the LIGO map in a fixed time window from T0 to T0+10 ks. No significant new sources are found. We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky. Again, no significant candidate counterpart was found. Energy flux upper bounds for the fixed time interval between 100 MeV and 100 GeV for this search vary between 2e-10 and 3e-09 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Elisabetta Bissaldi (Elisabetta.Bissaldi@ba.infn.it). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.