TITLE:   GCN CIRCULAR
NUMBER:  24648
SUBJECT: LIGO/Virgo S190521g: Upper limits from CALET observations 
DATE:    19/05/22 03:01:56 GMT
FROM:    Yuta Kawakubo at Louisiana State U./CALET  <kawakubo1@lsu.edu>

Y. Asaoka (Waseda U),  A. Yoshida, T. Sakamoto,
V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU),
K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
S. Ozawa, 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:

At the trigger time of the compact binary merger candidate S190521g,
T0 = 2019-05-21 03:02:29.447 UT (The LIGO Scientific Collaboration 
and  Virgo Collaboration, GCN Circ. 24621), the CALET Gamma-ray
Burst Monitor (CGBM) high voltages were off (from T0-8 min to 
T0+8 min).

The CALET Calorimeter (CAL) was operating in the high energy trigger 
mode at the trigger time of S190521g. Using 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.   The
90% upper limit of CAL is 6.0x10^-6 erg/cm2/s (10-100 GeV) when the
summed LIGO-Virgo probability reaches 30%. The CAL FOV was 
centered at RA=205.7 deg, Dec=49.2 deg at T0.