TITLE: GCN CIRCULAR NUMBER: 27144 SUBJECT: LIGO/Virgo S200219ac: Fermi GBM transient event not confidently associated with GW signal DATE: 20/02/19 21:57:24 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH) reports on behalf of the Fermi-GBM Team: For S200219ac and using the initial BAYESTAR skymap, Fermi-GBM was observing 46.6% of the localization probability at event time; the southern lobe was Earth-occulted for GBM. There was a Fermi-GBM onboard trigger, GRB 200219B (GCN 27127), approximately 10 min after the LIGO/Virgo detection of the GW trigger (GCN 27130). However due to the temporal offset and spatial inconsistency, we do not consider these two events associated. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates +/- 1 hour around the GW event time. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time for S200219ac. The targeted search identified a transient at approximately T0+11 s that is consistent with a short GRB origin and spatially consistent with the initial S200219ac localization map. The SNR of this event is 5.6, and the False Alarm Rate for signals of this significance in GBM data is 3.0E-4 Hz. However, due to the weak nature of the event, the rate of events of similar significance in GBM, and the presence of multiple galactic transient signals around the time of interest, we are not confident in an association. For the interested observer, the GBM localization HEALPix file can be found on the Gravitational Wave Treasure Map (Wyatt et al. 2020, arXiv:2001.00588) at: http://treasuremap.space/static/S200219ac_GBM_Event1_healpix.fit. The skymap image can be found at: http://treasuremap.space/static/S200219ac_GBM_Event1_skymap.png.