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GCN Circular 27149

Subject

LIGO/Virgo S200219ac: No transient candidates in CALET observations

Date

2020-02-20T04:51:24Z (5 years ago)

From

Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@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 S200219ac T0 = 2020-02-19 09:44:15.195 UT (The LIGO Scientific 
Collaboration and Virgo Collaboration, GCN Circ. 27130Not found
 
 
).

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 23 % and 48 %, respectively (and 73 % credible region of the
updated localization map was above the horizon).  The HXM and SGM fields
of view were centered at RA = 294.7 deg, Dec = +61.4 deg and 
RA =298.3 deg, Dec = +51.6 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 S200219ac. 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. There 
was no significant overlap with the LVC high probability localization 
region at T0+-60 sec. The CAL FOV was centered at RA = 298.5 deg,
Dec = +51.6 deg at T0.