GCN Circular 24185
Subject
LIGO/Virgo S190425z: Fermi GBM Observations
Date
2019-04-25T15:35:23Z (5 years ago)
From
Cori Fletcher at USRA/NASA <corinne.l.fletcher@nasa.gov>
C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group:
For S190425z and using the initial BAYESTAR skymap, Fermi-GBM was
observing 55.6% of the probability region at event time.
There was no Fermi-GBM onboard trigger around the event time of
the LIGO/Virgo detection of GW trigger S190425z (GCN 24168).
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.
Assuming a detectable relativistic jet, it likely originated from the
44% of the LVC localization behind the Earth for Fermi, located at
RA=194.64, Dec=22.47 with a radius of 67.2 degrees. This region is
also consistent with the highest probability density region of the
BAYESTAR map. Otherwise, we set the following upper limits for the
remaining 90% localization region not blocked by the Earth. Using
the representative soft, normal, and hard GRB-like spectral 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
------------------------------------
0.1 s: 4.2-117 8.8-84. 27.-93.
1.0 s: 1.3-35. 2.7-25. 7.8-28.
10 s: 0.4-11. 0.9-7.7 2.4-8.7
Assuming the mean luminosity distance of ~155 Mpc from the GW
detection, we estimate intrinsic luminosity upper limits of
(0.03-5.1)E49 erg/s for the soft template, (0.04-3.4e)E49 erg/s
for the normal template, and (0.2-6.2)E49 erg/s for the hard template
over the 1 keV-10 MeV energy range.