GCN Circular 21072

R. Hamburg (UAH) and C. 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), Adam
Goldstein (USRA), 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)

At the time of the G284239, Fermi was passing through the South Atlantic
Anomaly; therefore the GBM detectors were disabled.

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: 0.07 0.56 0.10 Crab
 27- 50 keV: 0.13 0.84 0.17 Crab
 50-100 keV: 0.18 1.16 0.25 Crab
100-300 keV: 0.34 1.98 0.46 Crab
300-500 keV: 2.20 13.15 3.15 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.