GCN Circular 25647
Subject
LIGO/Virgo S190901ap: Upper limits from CALET observations.
Date
2019-09-04T07:06:55Z (6 years ago)
From
Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>
N. Cannady (GSFC/UMBC), A. Yoshida, T. Sakamoto, V. Pal'shin,
S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), Y. Asaoka, S. Torii (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger
time of S190901ap T0 = 2019-09-01 23:31:01.838 UT (The LIGO Scientific
Collaboration and Virgo Collaboration, GCN Circ. 25606 and 25614).
No CGBM on-board trigger occurred around the event time. Based
on the LIGO-Virgo localization sky map, the summed LIGO probabilities
inside the CGBM HXM (7 - 3000 keV) and SGM (40 keV - 28 MeV) fields
of view are 6 % and 61 %, respectively (and 82 % credible region
of the updated localization map was above the horizon). The HXM and
SGM fields of view were centered at RA = 345.1 deg, Dec = 22.4 deg
and RA = 353.8 deg, Dec = 16.7 deg at T0, respectively.
Based on the analysis of the light curve data with 0.125 sec
time resolution from T0-60 sec to T0+60 sec, we found no
significant excess (signal-to-noise ratio >= 7) around the trigger
time in either the HXM or the SGM data.
The CALET Calorimeter (CAL) was operating in the low energy trigger
mode at the trigger time of S190901ap. Using the CAL data, we have
searched for gamma-ray events in the 1-10 GeV band from -60 sec
to +60 sec from the GW trigger time and found no candidates
in the overwrap region with the LIGO-Virgo probability map.
The 90% upper limit of CAL is 6.3x10^-5 erg/cm^2/s (1-10 GeV) when
the summed LIGO-Virgo probability reaches 5%.
The CAL FOV was centered at RA= 353.8 deg, Dec= 16.6 deg at T0.