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GCN Circular 26645

Subject
LIGO/Virgo S200105ae: Upper limits from Fermi-GBM Observations
Date
2020-01-06T20:30:43Z (4 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres (UAH) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group

For S200105ae and using the latest BAYESTAR skymap, Fermi-GBM was observing
82.3% 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 S200105ae (GCN Circ. 26640). 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=255.8, Dec=22.4 with a radius of 67.4 degrees. We therefore set upper
limits on impulsive gamma-ray emission for the LVC localization region
visible to Fermi at merger time. 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:    4.0    6.3    11
1.024 s:    1.1    1.8    4.4
8.192 s:    0.40    0.63    1.3

Assuming the median luminosity distance of 265 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:     5.1        7.5    21
1.024s:     1.4       2.1    8.6
8.192s:    0.51    0.75    2.5
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