//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31343 SUBJECT: GRB 211231A: Fermi GBM Final Real-time Localization DATE: 21/12/31 07:11:46 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 07:00:31 UT on 31 Dec 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 211231A (trigger 662626836.787242 / 211231292). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 292.2, Dec = -24.9 (J2000 degrees, equivalent to J2000 19h 28m, -24d 53'), with a statistical uncertainty of 1.8 degrees. The angle from the Fermi LAT boresight is 62.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211231292/quicklook/glg_skymap_all_bn211231292.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211231292/quicklook/glg_healpix_all_bn211231292.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211231292/quicklook/glg_lc_medres34_bn211231292.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31345 SUBJECT: GRB 211231A: GECAM detection DATE: 21/12/31 14:40:56 GMT FROM: Xiaolu Zhang at IHEP Z. W. Guo, S. L. Xiong, G. Y. Zhao，X. L. Zhang , S. Xiao, C. Cai, J. J. He, Y. Huang,C. Y. Li, X. B. Li, J. C. Liu, X. Y. Song,Y. Zhao, P. Wang, S. L. Xie, W. C. Xue,Q. B. Yi, Y. Q. Zhang, X. Y. Zhao, C. Zheng, Y. Q. Du, D. Y. Guo, J. Liang, F. J. Lu, Q. Luo, X. Ma, W. X. Peng, R. Qiao, L. M. Song, J. Wang, H. Wu, P. Zhang, S. N. Zhang, Z. Zhang,C. W. Wang, S. J. Zheng (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered in-flight by a long bright burst, GRB 211231A, at 2021-12-31T07:00:35.050 UTC (denoted as T0)， which was also observed by Fermi/GBM (GCN #31343). According to the BDS alert data, this burst mainly consists of a broad pulse with a duration of about 15 s. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GRB211231Alc.png 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: 295.1 deg dec: -7.0 deg err: 5.0 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. 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: 31367 SUBJECT: GRB 211231A: AstroSat CZTI detection DATE: 22/01/02 12:16:26 GMT FROM: Gaurav Waratkar at IIT,Bombay V. Prasad (IUCAA), A. Suresh (IITB), G. Waratkar (IITB), A. Vibhute (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., 2021, JApA, 42, 73) showed detection of a long GRB 211231A which was also detected by Fermi-GBM (GCN 31343) and GECAM (Guo et al. GCN 31345). The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2021-12-31 07:00:35.75 UT. The measured peak count rate associated with the burst is 193 (+60, -27) cts/s above the background in the combined data of three quadrants, with a total of 599 (+188, -196) cts. The local mean background count rate was 362 (+4, -4) cts/s. Using cumulative rates, we measure a T90 of 13 (+1, -7) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2021-12-31 07:00:35.88 UT. The measured peak count rate is 562 (+73, -75) cts/s above the background in the combined Veto data of four quadrants, with a total of 1536 (+452, -569) cts. The local mean background count rate was 1590 (+4, -4) cts/s. We measure a T90 of 8 (+3, -6) s from the cumulative Veto light curve. 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.