GRB 210126A

D. Nadella (NITK), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), P. Sawant (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA),
A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the
AstroSat CZTI collaboration: 

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a long GRB 210126A, which
was also detected by Fermi-GBM (GCN #29354
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 ) and GECAM-B (GCN #29356
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 ). 

The source was detected in the 20-200 keV energy range in three
quadrants (Quadrant A, C, and D). Quadrant D was noisy, and we excluded
it from further analysis. The light curve showed multiple peaks of
emission with the strongest peak at 2021-01-26 10:00:07 UT. The measured
peak count rate associated with the burst is 56 (+9, -10) cts/s above
the background in the combined data of two quadrants, with a total of
1039 (+412, -454) cts. The local mean background count rate was 248 (+1,
-1) cts/s. Using cumulative rates, we measure a T90 of 67 (+41, -55) s.
These large error bars arise from the presence of a weak second peak
whose association with the burst is ambiguous in our data. 

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.

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

During the commissioning phase, GECAM-B was triggered in-flight by
a long burst at 2021-01-26T10:00:10.600 UTC (denoted as T0).
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
multiple pulses with a duration of roughly 60 s.
An automatic on-ground localization was calculated using the light curves
and spectrum. 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: 112.9 deg Dec: -53.3 deg
Galactic lon: 266.6 deg, lat: -20.6 deg
Err: 6 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.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_5-21-4_65354410.png

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_65354410_V01.png

This burst is temporally and positional coincident with Fermi/GBM trigger
(trigNum 633348010, GCN #29354
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 ).

As the detailed science data are downloaded, all analyses would be improved.

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).

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
 at 10:00:05 on 26 Jan. 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 90.2+/-6.6 deg
Decl.(2000.0) = -66.0+/-3.3 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210126417/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210126417/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210126417/json