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TITLE:   GCN CIRCULAR
NUMBER:  22653
SUBJECT: GRB 180416B: CALET Gamma-Ray Burst Monitor detection
DATE:    18/04/18 12:47:28 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

Y. Kawakubo, A. Yoshida, T. Sakamoto, V. Pal'shin, A. Tezuka, S. Matsukawa,
H. Onozawa (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:

The long-duration GRB 180416B (Fermi-GBM trigger #545609416; Konus-Wind trigger
time on 22:10:10.60 UT) triggered the CALET Gamma-ray Burst Monitor (CGBM) at
22:10:09.279 UTC on 16 April 2018. The burst signal was seen by all CGBM detectors.

The burst light curve shows a single pulse which starts at T+1.6 sec, peaks at
T+3.1 sec and ends at ~T+14 sec, followed by a weak tail seen up to ~T+62 sec.
The T90 and the T50 durations measured by the SGM data are 51.6 +- 12.7 sec
and 17.4 +- 8.4 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1207951766/

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

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TITLE:   GCN CIRCULAR
NUMBER:  22681
SUBJECT: GRB 180416B: AstroSat CZTI detection
DATE:    18/05/04 17:30:55 GMT
FROM:    Vidushi Sharma at IUCAA  <vidushi@iucaa.in>

V. Sharma (IUCAA), V. Bhalerao (IIT-B), D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed the detection of a long GRB 180416B, which was also detected by CALET (Kawakubo Y. et al., GCN 22653) along with Fermi-GBM (trigger #545609416) and Konus-Wind trigger time on 22:10:10.60 UT.

The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak of emission with peak at 22:10:12.50 UT. The measured peak count rate is 388 cts/s above the background in combined data of four quadrants, with a total of 5491 cts. The local mean background count rate was 526.8 cts/s. Using cumulative rates, we measure a T90 of 56.3 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.