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GCN Circular 24735

Subject
LIGO/Virgo S190602aq: Upper limits from CALET observations
Date
2019-06-04T03:25:42Z (5 years ago)
From
Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>
S. Torii (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, 
S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa (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),

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the
trigger time of S190602aq T0 = 2019-06-02 17:59:27.089 UT (The
LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ.
24717).

No CGBM on-board trigger occurred around the event time.  Based
on the LIGO-Virgo localization sky map, most 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 11% and 70%, respectively
(and 99% credible region of the initial localization map was above
the horizon).  The HXM and SGM fields of view were centered at
RA = 118.5 deg, Dec = 53.8 deg and  RA = 127.2 deg, Dec = 45.5 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 high energy
trigger mode at the trigger time of S190602aq. Using the CAL data,
we have searched for gamma-ray events in the 10-100 GeV
band from -60 sec to +60 sec from the GW trigger time and
found no candidates.
The 90% upper limit of CAL is 2.9x10^-4 erg/cm^2/s (10-100 GeV) when
the summed LIGO-Virgo probability reaches 5%.
The CAL FOV was centered at RA= 127.5 deg, DEC= 45.1 deg at T0.
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