TITLE: GCN CIRCULAR NUMBER: 20797 SUBJECT: LIGO/Virgo G275697: Fermi GBM Upper Limits DATE: 17/03/02 20:48:23 GMT FROM: Adam Goldstein at Fermi/GBM Adam Goldstein (USRA) and Colleen Wilson-Hodge (NASA/MSFC) report on behalf of the GBM-LIGO Group: Lindy Blackburn (CfA), Michael S. Briggs (UAH), Jacob Broida (Carleton College), Eric Burns (UAH), Jordan Camp (NASA/GSFC), Tito Dal Canton (NASA/GSFC), Nelson Christensen (Carleton College), Valerie Connaughton (USRA), Rachel Hamburg (UAH), C. Michelle Hui (NASA/MSFC), Pete Jenke (UAH), Dan Kocevski (NASA/MSFC), Nicolas Leroy (LAL), Tyson Littenberg (NASA/MSFC), Julie McEnery (NASA/GSFC), Rob Preece (UAH), Judith Racusin (NASA/GSFC), Peter Shawhan (UMD), Karelle Siellez (GA Tech), Leo Singer (NASA/GSFC), John Veitch (Birmingham), Peter Veres (UAH) Fermi GBM observed 69% of the bayestar sky map at the time of the LIGO trigger, and we set the following flux upper limits for the entire visible sky map (excluded region is a circle with radius of 68 degrees centered on RA, Dec = 326.9, -22.8). Using a hard Band function with (Epeak, alpha, beta) = (500 keV, -0.5, -2.5), we set a 3 sigma, 1-second-averaged flux upper limit for any transient within 30 s of the LIGO trigger time in the 10-1000 keV band ranging from 4.6e-7 to 6.0e-7 erg/s-cm^2. Using an exponentially cutoff power law parametrized with (Epeak, index) = (566 keV, -0.42), which represents the average GBM-triggered short GRB, the upper limit ranges from 5.0e-7 to 6.4e-7 erg/s-cm^2. Using the Earth Occultation technique (Wilson-Hodge et al. 2012, ApJS, 201, 33) to estimate the amount of persistent emission during a 48-hour period centered on the LIGO trigger time, we place the following range of 3-sigma day-averaged flux upper limits based on observed sources over the entire LIGO sky map: Energy min max median -------------------------------- 12- 27 keV: 0.08 0.45 0.12 Crab 27- 50 keV: 0.14 0.66 0.20 Crab 50-100 keV: 0.17 0.80 0.24 Crab 100-300 keV: 0.34 1.67 0.49 Crab 300-500 keV: 1.85 10.2 2.55 Crab These limits are based on the minimum requirement that each source in the Earth Occultation catalog was Earth-occulted at least 6 times in each of the 24 hour periods preceding and following the LIGO trigger and that the occultations were well separated from nearby bright sources.