TITLE:   GCN CIRCULAR
NUMBER:  33897
SUBJECT: LIGO/Virgo/KAGRA S230529ay: Upper limits from CALET observations. 
DATE:    23/05/30 19:42:13 GMT
FROM:    Yuta Kawakubo at Louisiana State University <kawakubo1@lsu.edu>

S. Sugita, A. Yoshida, T. Sakamoto (AGU), Y. Kawakubo (LSU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR),
S. Torii, Y. Akaike, K. Kobayashi (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 
S230529ay T0 = 2023-05-29 18:15:00 UT (The LIGO Scientific 
Collaboration, the Virgo Collaboration, the KAGRA Collaboration, 
GCN Circ. 33889, 33891) the CALET Gamma-ray Burst Monitor
(CGBM) high voltages were off (from T0-2 min to T0+3 min).

The CALET Calorimeter (CAL) was operating in the high energy trigger
mode at the trigger time of S230529ay. Using the CAL data, we 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
LVK high probability localization region.  The 90% upper limit of CAL is 
1.2 x 10^-5 erg/cm^2/s (10-100 GeV) when the summed LVK probability reaches
20%. The CAL FOV was centered at RA = 118 deg, DEC = +47 deg at T0.

The preliminary CGBM analysis for O4 events can be found here:
http://cgbm.calet.jp/cgbm_trigger/O4