TITLE:   GCN CIRCULAR
NUMBER:  29486
SUBJECT: GRB 210207B: GECAM detection
DATE:    21/02/12 03:32:43 GMT
FROM:    Zhao Yi at POLAR  <yizhao@ihep.ac.cn>

Y. Zhao, X. Y. Song, S. Xiao, C. Cai, S. L. Xiong, Y. Huang, C. Y. Li,
J. J. He, Q. B. Yi, B. X. Zhang, Y. Q. Zhang, S. Y. Zhao, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, 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,
J. C. Liu, 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, W. C. Xue, S. Yang, M. Yao,
C. Y. Zhang,D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, X. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, the ground search of GECAM-B data found
a long burst, GRB 210207B, at 2021-02-07T21:52:14.050 UTC (T0), which
was also reported by Swift/BAT (GCN #29420, #29435), Konus/Wind (GCN #29426),
AGILE (GCN #29428) and Insight-HXMT/HE (GCN #29434). 
The later bright pulse also triggered GECAM-B in-flight.

According to the GECAM-B light curves in about 8 keV-4 MeV, this burst
mainly consists of multiple pulses with a duration (T90) of 45.0 +/- 4.5 s
starting from T0 - 1.8 s. The 1-s peak counts rate is about 1300 cps
while the total counts is about 4600 counts.

Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):

Ra: 275.00 deg Dec: 51.57 deg
Err: 8.23 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.

This position is consistent with Swift (GCN #29420) within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GECAM-B-tn210207_215215.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).