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GCN Circular 26924

Subject

LIGO/Virgo S200128d: Upper limits from CALET observations

Date

2020-01-29T06:06:04Z (4 years ago)

From

Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>

N. Cannady (GSFC/UMBC),  A. Yoshida, T. Sakamoto,
V. Pal'shin, 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), 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 S200128d T0 = 2020-01-28 02:20:11.903 UT (The LIGO Scientific
Collaboration and Virgo Collaboration, GCN Circ.26906Not found
 
 
).

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 26 % and 49 %, respectively (and 65 % credible region of the
initial sky map was above the horizon).  The HXM and SGM fields of
view were centered at RA = 134.1 deg, Dec = +30.5 deg and RA = 126.1 
deg, Dec = +23.4 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 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 S200128d. 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 in the
overwrap region with the LIGO-Virgo high probability localization
region. 

The 90% upper limit of CAL is 4.6 x 10^-6 erg/cm^2/s (10-100 GeV) 
when the summed LIGO-Virgo probability reaches 10%.
The CAL FOV was centered at RA = 126.1 deg, DEC = +23.4 deg at
T0.