TITLE: GCN CIRCULAR NUMBER: 24605 SUBJECT: LIGO/Virgo S190519bj: Fermi GBM Observations DATE: 19/05/19 20:05:57 GMT FROM: Suraj Poolakkil at UAH S. Poolakkil (UAH) and R. Hamburg (UAH) report on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group: For S190519bj, and using the initial BAYESTAR skymap, Fermi-GBM was observing 32.0% of the localization probability at event time. There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo detection of GW trigger S190519bj (GCN 24598). An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. Part of the LVC localization region is behind the Earth for Fermi, located at RA = 53.1 and Dec = 15.4 with a radius of 67.5 degrees. We therefore set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like spectral templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by the remaining visible GW localization probability (in units of erg/s/cm^2): Timescale soft norm hard -------------------------------------- 0.128 s: 1.3e-07 2.1e-07 4.6e-07 1.024 s: 3.9e-08 6.2e-08 1.4e-07 8.192 s: 1.4e-08 1.6e-08 3.8e-08 Assuming the median luminosity distance of ~3154 Mpc from the GW detection, we estimate intrinsic luminosity upper limits of (2.6-24.3)E49 erg/s for the soft template, (2.5-34.0)E49 erg/s for the normal template, and (1.0-12.6)E50 erg/s for the hard template over the 1 keV-10 MeV energy range.