[vsnet-grb-info 20965] GRB 180701A/MAXI J2119-045: CALET Gamma-Ray Burst Monitor data search

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23063
SUBJECT: GRB 180701A/MAXI J2119-045: CALET Gamma-Ray Burst Monitor data search
DATE:    18/07/31 03:04:31 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

V. Pal'shin, Y. Kawakubo, T. Sakamoto, A. Yoshida, S. Sugita, A. Tezuka,
S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (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:

We have performed a search of hard X-ray/gamma-ray emission
from GRB 180701A/MAXI J2119-045 (Maruyama et al., GCN Circ. 22880)
in the CALET Gamma-ray Burst Monitor (CGBM) data around
the MAXI trigger time at T0=06:47 UT on 2018 July 1.

The source position (RA, Dec (J2000) = 319.919 deg, -4.500 deg)
at the trigger time was in the CGBM FOV at favorable angles (the off-axis
angles 22.1 deg and 12.2 deg for HXM and SGM detector respectively).

No CGBM on-board trigger occurred around T0.
By using the CGBM time-history data (0.125 sec time resolution),
we found no statistically significant signal between +-50 sec from T0.
We estimate 7-sigma upper limit in the 30-1000 keV band as
6x10^-7 erg/cm2/s assuming a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.0 and Ep = 200 keV in 1 s exposure.

At the time of the Konus-Wind event at 06:37:44 UTC (=T0-556 sec)
suggested to be the main part of GRB 180701A (Kozlova et al.,
GCN Circ. 22915), the position of the MAXI source was in the CGBM FoV
at favorable angles (the off-axis angles 44.9 deg and 40.4 deg
for HXM and SGM detector respectively).
For the reported Konus-Wind spectral parameters, the estimated response
in the CGBM detectors for the MAXI position would have a signal-to-noise
ratio up to 15 in individual TH channel and up to 18 in combination
of channels, while we do not see any hint of emission around this time.
Hence, we conclude that the Konus-Wind event is likely not related
to GRB 180701A/MAXI J2119-045.

The CALET data used in this analysis are provided by the Waseda
CALET Operation Center located at the Waseda University.