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GCN Circular 26664

Subject
LIGO/Virgo S200105ae: Upper limits from CALET observations.
Date
2020-01-08T06:11:55Z (4 years ago)
From
Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>
K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, V. Pal'shin, 
S. Sugita (AGU), Y. Kawakubo (LSU), 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 S200105ae T0 = 2020-01-05 16:24:26.057 UT (The LIGO Scientific
Collaboration and Virgo Collaboration, GCN Circ.26640).

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 71 % and 82 %, respectively (and 84 % credible region of the
initial sky map was above the horizon).  The HXM and SGM fields of
view were centered at RA = 42.4 deg, Dec =-23.7 deg and RA = 50.5 
deg, Dec = -30.6 deg at T0, respectively.

CGBM high voltages were turning on around T0-60 sec.  Based on the 
analysis of the light curve data with 0.125 sec time resolution from
T0-50 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 S200105ae. 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 6.5x10^-6 erg/cm^2/s (10-100 GeV) when
the summed LIGO-Virgo probability reaches 60%.
The CAL FOV was centered at RA= 50.6 deg, DEC= -30.6 deg at T0.
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