TITLE:   GCN CIRCULAR
NUMBER:  24593
SUBJECT: LIGO/Virgo S190517h: CALET Observations
DATE:    19/05/19 05:01:13 GMT
FROM:    Yuta Kawakubo at Louisiana State U./CALET  <kawakubo1@lsu.edu>

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

The high-voltage of the CALET Gamma-ray Burst Monitor (CGBM)
detectors were turned on around the  trigger time of S190517h, 
T0 = 2019-05-17 05:51:01.831 UT (The LIGO Scientific Collaboration
and Virgo Collaboration, GCN Circ. 24570): at T0-8 sec, T0, and
T0+8 sec for HXM1, HXM2, and SGM detector respectively. 

No CGBM on-board trigger occurred around the event time.  Based 
on the LIGO-Virgo localization sky map, the high probability area 
was out of the FOV of the HXM detectors, and partially in the FOV
of the SGM detector (the summed LIGO probabilities inside FOVs
are 0% and 61% respectively), 11% credible region of the initial
localization map  was Earth-occulted.  At T0, the HXM and SGM
FOVs were centered at RA  = 117.0 deg, Dec = -25.4 deg and 
RA = 126.0 deg, Dec = -31.6 deg, respectively.

Based on the analysis of the light curve data with 0.125 sec time 
resolution from T0-8 sec to T0+60 sec, we found no significant excess 
(signal-noise-ration >= 7) around the trigger time in either the HXM 
(7-3000 keV) or the SGM (40 keV - 28 MeV) data  (for the SGM, the 
interval is from T0+8 sec to T0+60 sec).  Also, there is no sign of the
weak excess reported by INTEGRAL SPI-ACS  at ~T0+37 s 
(Doyle et al., GCN Circ. 24571) 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 S190517h. 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. There is no significant overlap with the LVC
location probability map.  The CAL FOV was centered
at RA=126.2 deg, Dec=-31.9 deg at T0.