[vsnet-grb-info 24675] LIGO/Virgo S200115j: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26774
SUBJECT: LIGO/Virgo S200115j: Upper limits from Fermi-GBM Observations
DATE:    20/01/15 13:42:25 GMT
FROM:    Adam Goldstein at Fermi-GBM, USRA  <adam.michael.goldstein at gmail.com>

A. Goldstein (USRA) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group

For S200115j and using the latest BAYESTAR skymap, Fermi-GBM was observing
84.4% 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 S200115j (GCN Circ. 26759). 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=137.7, Dec=23.9 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:   4.6      8.3      17.
1.024 s:   1.5      2.8      6.1
8.192 s:   0.5      0.7      2.0

Assuming the median luminosity distance of 331 Mpc from the GW detection,
we estimate the following intrinsic luminosity upper limits over the 1
keV-10 MeV energy range (in units of 10^48 erg/s):

Timescale  Soft     Normal   Hard
---------------------------------
0.128s:    9.2      15.      52.
1.024s:    3.0      5.2      19.
8.192s:    0.9      1.3      6.1