[vsnet-grb-info 23787] LIGO/Virgo S190930s: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25886
SUBJECT: LIGO/Virgo S190930s: Upper limits from Fermi-GBM Observations
DATE:    19/09/30 19:52:14 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 S190930s and using the initial bayestar.fits.gz skymap, Fermi-GBM was observing 62.2% 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 S190930s (GCN 25871). 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.

We therefore set upper limits on impulsive gamma-ray emission. 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:   5.7      6.6      10.
1.024 s:   1.6      2.2      3.5
8.192 s:   0.6      0.7      1.0

Assuming the median luminosity distance of 752 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
------------------------------------
0.128 s:   5.94     6.29     15.8
1.024 s:   1.67     2.10     5.53
8.192 s:   0.62     0.65     1.58