TITLE: GCN CIRCULAR NUMBER: 26654 SUBJECT: LIGO/Virgo 200105ae: No counterpart candidates in Fermi-LAT observations DATE: 20/01/07 11:11:50 GMT FROM: Francesco Longo at U of Trieste,INFN Trieste F. Longo (University and INFN, Trieste), D. Kocevski (NASA/MSFC), 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 January 5th, 2020, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo sub threshold trigger S200105ae (GCN 26640). 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 time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had an instantaneous coverage of ~40% of the LIGO probability at the time of the trigger (T0 =2020-01-05 16:24:26 UTC), and reached ~75% cumulative coverage after about 5 ks. The remaining area was not observed within 10 ks following the trigger time of the event. We performed a search for a transient counterpart within the observed region of the 90% contour of LIGO map in a fixed time window from T0 to T0 + 10 ks. One significant excess (with TS>25) was found at R.A., Dec. = 215.6, 32.3, but it is likely associated with the known and currently active source OQ 334 (lies within the 90% uncertainty region). We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky, and no additional excesses were found. Energy flux upper bounds for the fixed time interval between 100 MeV and 1 GeV for this search vary between 1.1e-10 and 3.5e-07 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is F.Longo (francesco.longo@ts.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.