//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23547 SUBJECT: GRB 181222A: MAXI/GSC detection DATE: 18/12/22 07:43:15 GMT FROM: H. Negoro at Nihon U. A. Sakamaki, H. Negoro, M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita, T. Oeda, K. Shiraishi (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, T. Midooka (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, S. Ogawa (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source at 06:44:09 UT on December 22, 2018. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (270.731 deg, -38.848 deg) = (18 02 55, -38 50 52) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.13 deg and 0.12 deg, respectively. The roll angle of long axis from the north direction is 132.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 350 +- 34 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (270.981, -38.395) deg = (18 03 55, -38 23 42) (J2000) (R.A., Dec) = (270.687, -38.351) deg = (18 02 44, -38 21 03) (J2000) (R.A., Dec) = (270.409, -39.448) deg = (18 01 38, -39 26 52) (J2000) (R.A., Dec) = (270.708, -39.494) deg = (18 02 49, -39 29 38) (J2000) There was no significant excess flux in the previous transit at 05:11 UT with an upper limit of 20 mCrab. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23548 SUBJECT: GRB 181222A: Fermi GBM observation DATE: 18/12/22 17:37:52 GMT FROM: Peter Veres at UAH P. Veres (UAH) and E. Bissaldi (Politecnico & INFN Bari) report on behalf of the Fermi GBM Team: "At 06:41:34.25 UT on 22 December 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 181222A (trigger 567153699 / 181222279) which was also detected by MAXI/GSC (Sakamaki et al., GCN 23547). The GBM on-ground location is consistent with the MAXI position. The angle from the Fermi LAT boresight at the GBM trigger time is 89 degrees. The GBM light curve shows four separate pulses with a duration (T90) of about 131 s (50-300 keV). The time-averaged spectrum from T0-1 s to T0+151 s is adequately fit by a Band function with Epeak = 264 +/- 32 keV, alpha = -0.95 +/- 0.04, and beta = -1.47 +/- 0.01. The event fluence (10-1000 keV) in this time interval is (1.83 +/- 0.01)E-4 erg/cm^2. The 1-sec peak photon flux measured starting from T0+94.9 s in the 10-1000 keV band is 74.7 +/- 0.7 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23553 SUBJECT: GRB 181222A: CALET Gamma-Ray Burst Monitor detection DATE: 18/12/24 05:13:55 GMT FROM: Valentin Pal'shin at AGU T. Sakamoto, A. Yoshida, V. Pal'shin, S. Sugita, Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 181222A (MAXI/GSC detection: Sakamaki et al., GCN Circ. 23547; Fermi-GBM observation: Vere & Bissaldi, GCN Circ. 23548) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 06:41:33.811 UTC on 22 December 2018. The burst signal was seen by all CGBM detectors. Since the burst incident direction was nearly perpendicular to the HXM detector axes, the signal in these detectors was heavily attenuated. The burst light curve shows two main emission episodes which start at T+1.5 sec and end at T+105.8 sec. The T90 and the T50 durations measured by the SGM data are 98.3 +- 5.3 sec and 44.6 +- 39.7 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1229496031/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23559 SUBJECT: Konus-Wind observation of GRB 181222A DATE: 18/12/25 11:35:12 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 181222A (MAXI/GSC detection: Sakamaki et al., GCN Circ. 23547; Fermi/GBM observation: Veres & Bissaldi, GCN Circ. 23548; CGBM detection: Sakamoto et al., GCN Circ. 23553) triggered Konus-Wind at T0=24090.989 s UT (06:41:30.989). The burst light curve shows a multipeaked structure started at ~T0-1.3 s with a total duration of ~171.5 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of 3.97(-0.33,+0.32)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+94.208 s, of 6.71(-0.66,+0.66)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+146.688 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.05(-0.08,+0.08), the high energy photon index beta = -1.90(-0.12,+0.09), the peak energy Ep = 570(-100,+133) keV (chi2 = 79/84 dof). The spectrum near the maximum count rate (measured from T0+93.440 to T0+96.000 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.87(-0.06,+0.06), the high energy photon index beta = -2.01(-0.10,+0.08), the peak energy Ep = 850(-114,+136) keV (chi2 = 115/77 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB181222_T24090/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23566 SUBJECT: GRB 181222A: AstroSat CZTI detection DATE: 18/12/27 09:35:44 GMT FROM: Vidushi Sharma at IUCAA V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of a long GRB 181222A, which was also detected by MAXI/GSC (Negoro H. et al., GCN 23547), Fermi/GBM (Veres P. et al., GCN 23548), CALET (Sakamoto T. et al., GCN 23553) and Konus-Wind (Kozlova A. et al., GCN 23559). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 06:43:09.500 UT. The measured peak count rate is 1720 cts/s above the background in combined data of four quadrants, with a total of 14364 cts. The local mean background count rate was 522 cts/s. Using cumulative rates, we measure a T90 of 117 s. In preliminary analysis, we find that 1258 compton events are associated with this event. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. 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.