TITLE:   GCN CIRCULAR
NUMBER:  25536
SUBJECT: LIGO/Virgo S190828j: No transient candidates in CALET observations
DATE:    19/08/29 04:10:29 GMT
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),
and the CALET collaboration:


The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger 
time of S190828j T0 = 2019-08-28 06:34:05.756 UT (The LIGO
Scientific Collaboration and Virgo Collaboration, GCN Circ. 25497).

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 both 42 % (and 42 % credible region of the updated localization 
map was above the horizon).  The HXM and SGM fields of view were 
centered at RA = 5.4 deg, Dec = 18.4 deg and RA = 13.9 deg, 
Dec = 12.7 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 high energy
trigger mode at the trigger time of S190828j, but the CAL FOV 
does not have any overlap with the high probability localization region.
The CAL FOV was centered at RA= 13.9 deg, DEC= 12.6 deg at T0.