[vsnet-grb-info 24362] LIGO/Virgo S191216ap: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26461
SUBJECT: LIGO/Virgo S191216ap: Upper limits from Fermi-GBM Observations
DATE:    19/12/17 02:19:46 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood at nasa.gov>

J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group

For S191216ap and using the initial bayestar.fits.gz skymap, Fermi-GBM was observing 99.8% 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 S191216ap (GCN 26454). 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 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, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:   5.7      8.5      16.
1.024 s:   2.1      3.6      5.7
8.192 s:   0.7      1.0      2.0

Assuming the median luminosity distance of 324 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:    11.      15.      47.
1.024s:    4.0      6.4      17.
8.192s:    1.4      1.8      5.9