[vsnet-grb-info 23742] LIGO/Virgo S190924h: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25841
SUBJECT: LIGO/Virgo S190924h: Upper limits from Fermi-GBM Observations
DATE:    19/09/24 12:05:42 GMT
FROM:    Eric Burns at GSFC  <erickayserburns at gmail.com>

E. Burns (NASA/GSFC) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group

For S190924h and using the initial bayestar skymap, Fermi-GBM was observing
100% 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 S190924h (GCN 25829). 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 set upper limits on impulsive gamma-ray emission for the LVC
localization region. 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:     5.9     8.9     15.
1.024 s:     1.6     3.0     5.4
8.192 s:     0.3     0.6     1.1

Assuming the median luminosity distance of 514 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:     2.7          3.8         11.
1.024 s:     0.7          1.3         3.8
8.192 s:     0.1          0.3         1.1