[vsnet-grb-info 20858] GRB 180715A: CALET Gamma-Ray Burst Monitor detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22956
SUBJECT: GRB 180715A: CALET Gamma-Ray Burst Monitor detection
DATE:    18/07/18 06:03:29 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, Y. Kawakubo,
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 (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 short, hard GRB 180715A (Swift-BAT trigger #848048:
Ukwatta, et al., GCN Circ. 22947, 22951; Fermi-GBM detection:
Hamburg and Meegan, GCN Circ. 22952) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 18:07:04.799 UTC on 15 July 2018.
The burst signal was seen by all CGBM detectors.

The burst light curve shows a double-peaked pulse which starts
at T+0.192 sec and ends at T+0.784 sec.
The T90 and the T50 durations measured by the SGM data are
0.53 +- 0.07 sec and 0.34 +- 0.12 sec (40-1000 keV), respectively.

The time-averaged spectrum of the burst (measured by the SGM from
T+0.192 sec to T+0.784 sec) is best fit in the 0.03-10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.64(-0.37, +0.46) and Ep = 707(-195, +337) keV (chi2 = 29.4/32 dof).
The resulting fluence in this energy range is 2.32(-0.50, +0.65)x10^-6 erg/cm2.
The quoted errors are at 90% CL.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1215713118/

All the quoted values are preliminary.

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