LIGO/Virgo G275697: Fermi GBM Upper Limits
Abstract
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.
- Publication:
-
GRB Coordinates Network
- Pub Date:
- March 2017
- Bibcode:
- 2017GCN.20797....1G