[vsnet-grb-info 25294] LIGO/Virgo S200316bj: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27394
SUBJECT: LIGO/Virgo S200316bj: Upper limits from Fermi-GBM Observations
DATE:    20/03/17 03:24:48 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood at nasa.gov>

J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group

For S200316bj and using the initial bayestar.fits.gz,1 skymap, Fermi-GBM was observing 33.4% 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 S200316bj (GCN 27388). 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=58.3, Dec=19.5 with a radius of 67.2 degrees. We therefore set upper limits on impulsive gamma-ray emission for the LVC localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:   1.7      2.5      5.3
1.024 s:   0.4      0.8      1.8
8.192 s:   0.2      0.3      0.5

Assuming the median luminosity distance of 1222 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^49 erg/s):

Timescale  Soft     Normal   Hard
------------------------------------
0.128s:    4.7      6.2      22.
1.024s:    1.1      2.0      7.5
8.192s:    0.5      0.7      2.2