GRB 180221B

S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, V. Pal'shin,
Y. Kawakubo, M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (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), A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The long GRB 180221B (Konus-Wind trigger time on 12:30:00.79) triggered
the CALET Gamma-ray Burst Monitor (CGBM) at 12:29:59.616 UTC on
21 February 2018.  The burst signal was seen by all CGBM detectors.

The burst light curve shows a multi-peaked structure which starts at T0,
peaks at T0+16 sec and ends at T0+78 sec.  The T90 and the T50 durations
measured by the SGM data are 66.6 +- 6.8 sec and 21.1 +- 6.3 sec
(40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1203251126/

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

Y. Zhu, X. Ma, S. L. Xiong, X. B. Li, C. K. Li, Y. Huang, J. Y. Liao,
C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, X. F. Lu, J. L. Zhao, A. M. Zhang, 
Y. F. Zhang, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU),
F. J. Lu, L. M. Song, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP),
report on behalf of the Insight-HXMT team:

At 2018-02-21T12:30:01.000 (T0), the Insight-HXMT detected 
GRB 180221B (trigger ID: HEB180221520) in a routine search of the data, 
which was also observed by CALET/CGBM (GCN Circ. 22438
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 ).

The Insight-HXMT light curve mainly consists of multi-pulses 
with a duration (T90) of 65.8 s measured from T0+1.05 s.  
The 1-second peak rate, measured from T0+13.0 s, is 2888.2 cnts/sec. 
The total counts from this burst is 44805.8 counts. 

URL_LC: http://www.hxmt.org/images/GRB/HEB180221520_lc.jpg 

All measurements above are made with the CsI detectors operating in the 
regular mode with the energy range of about 80-800 keV (record energy). 
Only gamma-rays with energy greater than about 200 keV can penetrate 
the spacecraft and leave signals in the CsI detectors installed inside 
of the telescope. 

The analysis results presented above are preliminary; 
final results will be published elsewhere.

Insight-HXMT is the first Chinese space X-ray telescope, which was funded 
jointly by the China National Space Administration (CNSA) and the Chinese 
Academy of Sciences (CAS). More information about it could be found at: 
http://www.hxmt.org/index.php/enhome .