TITLE:   GCN CIRCULAR
NUMBER:  29338
SUBJECT: GECAM In-Flight Trigger of GRB 210120A
DATE:    21/01/20 14:43:51 GMT
FROM:    Shaolin Xiong at IHEP  <xiongsl@ihep.ac.cn>

Z. H. An, C. Cai, G. Chen, W. Chen, M. Gao, M. Y. Ge, K. Gong, D. Y. Guo,
J. J. He, Y. Huang, B. Li, C. Li, C. Y. Li, J. H. Li, M. S. 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, J. Y. Shi,
D. L. Shi, L. M. Song, X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, C. W. Wang, P. Wang, W. S. Wang, X. Y. Wen, S. Xiao,
S. L. Xiong, Y. B. Xu, Y. P. Xu, W. C. Xue, S. Yang, M. Yao, Q. B. Yi,
K. Zhang, P. Zhang, D. L. Zhang, F. Zhang, H. M. Zhang, S. N. Zhang,
Y. Q. Zhang, Z. Zhang, S. Y. Zhao, X. Y. Zhao, Y. Zhao, C. Zheng,
S. J. Zheng (IHEP), L. Chang, W. W. Chen, Y. M. Chen, L. Dong, X. B. Han,
J. Huang, J. Huang, C. Y. Ji, Y. C. Ji, F. Li, M. Y. Li, Z. D. Li,
Y. F. Lu, Y. Pang, J. L. Qi, J. G. Rong, Q. Q. Wang, Z. Wang, Y. Yang,
J. P. Yu, S. M. Yu, K. K. Zhang, D. K. Zhou (IAMCAS), M. Bai, T. Hu, Z. Ji,
Y. R. Liu, J. Su, C. X. Tian, J. Z. Tong, H. Y. Wu, Q. S. Yu, J. Zhong,
Z. M. Zou (NSSC), X. X. Feng (AIR),
(The GECAM Mission Team) report:

During the commissioning phase, one satellite of GECAM mission, GECAM-B,
was triggered by a long GRB 210120A at 2021-01-20T07:10:48.550 (T0),
which was also observed by Fermi/GBM (GCN #29334, 29335).

This burst was triggered, localized and classified as unknown source by
the GECAM In-Flight Trigger and Localization Software and
then 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 (including in-flight trigger
and location results) relative to the trigger time is about 60 seconds.
All other messages (including light curves data) for this trigger arrived
within about 10 minutes.

We made the quick-look light curve and the on-ground localization using the
alert data. The quick-look light curve shows that this burst mainly consists
of a single peak with a duration of about 20 s.
Although the in-flight calibration of energy response and localization
has not been finalized yet, the quick-look location is generally consistent
with the position given by Fermi/GBM within the error.
As the detailed science data are downloaded, all analyses including
localization would be further improved.

The GECAM quick-look light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210120_071048_GECAMb.png

The GECAM quick-look location (preliminary) could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210120_071048_GECAMb_Localization.png

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

This is the first GECAM GRB which was triggered and localized in-flight
with alert data promptly downlinked to ground successfully.

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).