[vsnet-grb-info 22829] LIGO/Virgo S190630ag: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24928
SUBJECT: LIGO/Virgo S190630ag: Upper limits from Fermi-GBM Observations
DATE:    19/07/01 00:42:27 GMT
FROM:    Cori Fletcher at USRA  <cfletcher at usra.edu>

C.A. Wilson-Hodge (NASA/MSFC) & R. Hamburg (UAH) on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group

For S190630ag and using the initial bayestar.fits skymap, Fermi-GBM was observing 87.7% 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 S190630ag (GCN 24922). 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 = 169.7 and Dec = -3.8 with a radius of 67.5 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
------------------------------------
0.1 s:     4.4        5.8     17.0
1.0 s:     1.1      1.9      4.4
10  s:     0.47     0.56     1.0

Assuming the median luminosity distance of 1059 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
------------------------------------
0.1 s:     9.2      10.       53.
1.0 s:     2.3      3.6       14.
10  s:     1.0      1.1       3.1