GRB 220131B
GCN Circular 31534
Subject
GRB 220131B: GECAM detection
Date
2022-01-31T08:34:33Z (3 years ago)
From
Zhao Yi at POLAR <yizhao@ihep.ac.cn>
Y. Zhao, S. L. Xiong, J. C. Liu, Y. Q. Zhang, C. Y. Li, S. L. Xie,
S. Xiao, C. Cai, P. Zhang, X. Y. Zhao, Y. Huang, X. Y. Song,
C. Zheng, Y. Zhao, Z. W. Guo, W. C. Xue, C. W. Wang,
Q. B. Yi, B. X. Zhang, W. X. Peng, R. Qiao, D. Y. Guo, X. B. Li,
X. Ma, L. M. Song, P. Wang, J. Wang, Z. Zhang, S. J. Zheng, W. Chen,
J. J. He, G. Y. Zhao, Y. Q. Du, H. Wu, J. Liang, Q. Luo, X. L. Zhang,
H. M. Zhang, Z. H. An, M. Gao, K. Gong, B. Li, C. Li, J. H. Li,
X. Q. Li, Y. G. Li, X. H. Liang, X. J. Liu, Y. Q. Liu, X. L. Sun,
Y. L. Tuo, J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang,
X. Zhou, F. J. Lu, S. N. Zhang (IHEP)
report on behalf of GECAM team:
During the commissioning phase, GECAM-B was triggered in-flight by a long burst,
GRB 220131B, at 2022-01-31T01:09:16.700 UTC (denoted as T0).
GECAM alert data was downlinked to the ground through the short message
service of BeiDou Navigation Satellite System (BDS) within ~60 s after T0.
According to the BDS alert data, this burst mainly consists of a single pulse
with a duration of about 20 s.
The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GRB220131B_lc.png
Using the automatic on-ground localization pipeline with the BDS alert data,
GECAM-B localized this burst to the following position (J2000):
Ra: 304.6 deg
Dec: 8.6 deg
Err: 3.2 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 preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GRB220131B_loc.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).
GCN Circular 31541
Subject
GRB 220131B: Swift/BAT-GUANO detection outside the coded FOV
Date
2022-02-01T18:46:38Z (3 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), James DeLaunay
(UAlabama), Jamie A. Kennea (PSU), report:
Swift/BAT did not localize GRB 220131B onboard (T0: 2022-01-31T01:09:16.7
UTC, GECAM GCN 31534).
The GECAM notice, distributed in near real-time, triggered the Swift
Mission Operations Center operated Gamma-ray Urgent Archiver for Novel
Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert
Telescope (BAT) to save 90 seconds of BAT event-mode data from [-50,+150]
seconds around the time of the burst. All the requested event mode data was
delivered to the ground.
The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu,
arXiv:2111.01769), detects the burst with a sqrt(TS) of 9.2 in a 2.048 s
analysis time bin.
NITRATES results are consistent with a burst coming from outside the coded
FOV, with DeltaLLHOut of 1.9. The best fit sky position from NITRATES is
consistent with the GECAM localization within the stated error (GCN 31534).
See Section 9.1 and Figure 20 in the NITRATES paper for brief descriptions
and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/