[vsnet-grb-info 23071] LIGO/Virgo S190727h: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25170
SUBJECT: LIGO/Virgo S190727h: Upper limits from Fermi-GBM Observations
DATE:    19/07/27 14:13:25 GMT
FROM:    C. Michelle Hui at MSFC/Fermi-GBM  <cmhui.astro at gmail.com>

 C. M. Hui(NASA/MSFC) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group

For S190727h and using the initial BAYESTAR skymap, Fermi-GBM was observing
65% 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 S190727h (GCN 25164). 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=288.0, Dec=21.0 with a radius of 67.2 degrees.  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 (in units of
10^-7 erg/s/cm^2):
Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     3.7     5.7    14.0
1.024 s:     1.2     2.8     5.8
8.192 s:     0.6     1.1     1.9

Assuming the median luminosity distance of 2022 Mpc from the GW detection,
we estimate the following intrinsic luminosity upper limits over the 1
keV-10 MeV energy range (in units of 10^50 erg/s):
Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     3.4          4.5        18.8
1.024 s:     1.1          2.2         7.8
8.192 s:     0.5          0.9         2.5