GCN Circular 25033
Subject
LIGO/Virgo S190707q: Upper limits from CALET observations
Date
2019-07-08T17:54:52Z (5 years ago)
From
Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu,
T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
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 S190707q T0 = 2019-07-07 09:33:26.181 UT (The
LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ.
25012).
No CGBM on-board trigger occurred around the event time. Based
on the LIGO-Virgo localization sky map, almost half of the high
probability area was within the field-of-view of the CGBM SGM.
The summed LIGO probabilities inside the CGBM HXM (7-3000 keV)
and SGM (40 keV - 28 MeV) fields of view are 26% and 58%, respectively
(and 76% credible region of the initial localization map was above
the horizon). The HXM and SGM fields of view were centered at
RA = 254.1 deg, Dec = 7.8 deg and RA = 262.4 deg, Dec = 2.2 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 S190707q. 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.
The 90% upper limit of CAL is 2.1x10^-6 erg/cm^2/s (1-10 GeV) when
the summed LIGO-Virgo probability reaches 20%.
The CAL FOV was centered at RA= 262.4 deg, DEC= 2.2 deg at T0.