[vsnet-grb-info 27786] GRB 210421A: GECAM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29889
SUBJECT: GRB 210421A: GECAM detection
DATE:    21/04/23 06:37:40 GMT
FROM:    QiBin Yi at IHEP, HXMT  <yiqb at ihep.ac.cn>

S. L. Xie, X. Y. Song, Q. B. Yi, X. Y. Zhao, Y. Huang, S. L. Xiong,
S. Xiao, C. Cai, Y. Zhao, J. C. Liu, Y. Q. Zhang, W. C. Xue, C. Zheng,
Z. W. Guo, C. W. Wang, D. Y. Guo, P. Wang, X. B. Li, W. X. Peng, R. Qiao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. 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,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, 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 triggered a long burst,
GRB 210421A, at 2021-04-21T00:27:32.000 UTC (denoted as T0),
which was also detected by Swift/BAT(GCN #29849). 

According to the GECAM-B light curves in about 8 keV - 115 keV, 
this burst mainly consists of multiple pulses with duration of about 20 s.

Although in-flight calibration has not been finalized yet, 
GECAM-B localized this burst to the following position (J2000):
Ra: 103.56 deg 
Dec: 2.26 deg 
Err: 3.46 deg (1-sigma,statistical only) 

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

GECAM location is consistent with the Swift/BAT(GCN #29849) position
within the error.

The GECAM light curve could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_2021-04-21T003A273A32.950_.pdf

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).