[vsnet-grb-info 21989] LIGO/Virgo S190408an: CALET Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24088
SUBJECT: LIGO/Virgo S190408an: CALET Observations
DATE:    19/04/10 11:14:51 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

S. Torii (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU),K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time
of S190408an (The LIGO Scientific Collaboration and Virgo Collaboration,
GCN Circ. 24069).  No CGBM on-board trigger occurred around the event time.
Based on the LIGO-Virgo localization sky map, most of the part of
the high probability area was in the field-of-view of CGBM.  The summed LIGO
probabilities inside the HXM and the SGM field of view are 91% and 95%.

Based on the analysis of the light curve data with 0.125 sec time resolution
from -60 sec to 60 sec from the trigger time, we found no significant excess
around the trigger time in either the HXM (7-3000 keV) or the SGM (40 keV -28 MeV)
data.

The CALET Calorimeter (CAL) was operating in low energy trigger mode at the trigger
time of S190408an.  Using CAL data, we have searched for gamma-ray events in
the 1-10 GeV band from -60 sec to +60 sec from the GW trigger time and found no
candidates.  The 90% upper limit of CAL is 2.3 x 10^-6 erg/cm2/s (1-10 GeV) when
the summed LIGO-Virgo probabilities reaches at 80%.