[vsnet-grb-info 28297] GECAM detection of a bright short burst from SGR 1935+2154

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30400
SUBJECT: GECAM detection of a bright short burst from SGR 1935+2154
DATE:    21/07/07 03:43:28 GMT
FROM:    Shuo Xiao at IHEP  <xiaoshuo at ihep.ac.cn>

S. Xiao, Y. Huang, X. Y. Zhao, S. L. Xiong, W. C. Xue, X. Y. Song, C. Cai,
S. L. Xie, J. C. Liu, C. Y. Li, Y. Q. Zhang,  Y. Zhao, Z. W. Guo, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, Q. B. Yi,
B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang,
K. Zhang, P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng,
X. Zhou (IHEP), report on behalf of GECAM team:

During the commissioning phase, GECAM-B was triggered in-flight by
a bright short burst (trig# 79317211) at 2021-07-07T00:33:31.700 UTC (T0),
which was also observed by Fermi/GBM (trig# bn210707023).
Its alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of
two overlapping pulses with a duration of about 100 ms.
Using the light curves and spectrum in the BDS alert data, 
GECAM-B localized this burst to the following position (J2000): 
Ra: 291.99 deg 
Dec: 24.30 deg
Err: 3.07 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees.

This location is consistent with SGR J1935+2154 within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/79317211_lc.png

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_bdm_79317211_V01.png

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).