[vsnet-grb-info 24503] LIGO/Virgo S191222n: No transient candidates in CALET observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26602
SUBJECT: LIGO/Virgo S191222n: No transient candidates in CALET observations 
DATE:    19/12/28 06:20:43 GMT
FROM:    Yuta Kawakubo at Louisiana State U./CALET  <kawakubo1 at lsu.edu>

V. Pal'shin, A. Yoshida, T. Sakamoto, 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), 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 S191222n T0 = 2019-12-22 03:35:37.119 UT (The LIGO Scientific 
Collaboration and Virgo Collaboration, GCN Circ. 26543, 26572).

No CGBM on-board trigger occurred around the event time.  Based on the
LVC high probability localization region, the summed LIGO probabilities
inside the CGBM HXM (7 - 3000 keV) and SGM (40 keV - 28 MeV) fields
of view are 6 % and 30 %, respectively (and 60 % credible region of the
updated localization map was above the horizon).  The HXM and SGM fields
of view were centered at RA = 337.7 deg, Dec = +4.6 deg and 
RA = 330.3 deg, Dec = -2.1 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 S191222n. 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. There 
is no significant overlap with the LVC high probability localization 
region at T0+-60 sec. The CAL FOV was centered at RA = 330.3 deg,
Dec = -2.1 deg at T0.