//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31534 SUBJECT: GRB 220131B: GECAM detection DATE: 22/01/31 08:34:33 GMT FROM: Zhao Yi at POLAR 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). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31541 SUBJECT: GRB 220131B: Swift/BAT-GUANO detection outside the coded FOV DATE: 22/02/01 18:46:38 GMT FROM: Aaron Tohuvavohu at U Toronto 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/