//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22423 SUBJECT: IPN Triangulation of GRB 180218A (long/bright) DATE: 18/02/19 16:54:13 GMT FROM: Dmitry Svinkin at Ioffe Institute D.Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, K. Hurley, on behalf of the IPN, V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, on behalf of the Fermi GBM team, and A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report: The long-duration, very bright GRB 180218A has been detected by Fermi(GBM; trigger 540659650), Konus-Wind, INTEGRAL(SPI-ACS), and Swift(BAT) at about 54845 s UT (15:14:05). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 46.279 (03h 05m 07s) +52.589 (+52d 35' 20") Corners: 49.798 (03h 19m 12s) +45.859 (+45d 51' 34") 50.993 (03h 23m 58s) +46.050 (+46d 03' 00") 41.217 (02h 44m 52s) +59.126 (+59d 07' 35") 39.654 (02h 38m 37s) +58.828 (+58d 49' 40") --------------------------------------------- The error box area is 12.13 sq. deg, and its maximum dimension is 14.48 deg (the minimum one is 51 arcmin). The Sun distance was 89 deg. This box may be improved. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB180218_T54845/IPN/ The time history and spectrum will be given in forthcoming GCN Circulars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22424 SUBJECT: GRB 180218A: Fermi GBM Detection DATE: 18/02/19 21:26:35 GMT FROM: Suraj Poolakkil at UAH S. Poolakkil (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 15:14:05.49 UT on 18 February 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180218A (trigger 540659650 / 180218635). This GRB was also triangulated by IPN (Svinkin et al., GCN 22423). The on-ground calculated location, using the GBM trigger data, is RA = 47.23, DEC = 46.65, with an uncertainty of 4 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ). The GBM light curve consists of a single bright peak with a duration (T90) of about 6 s (50-300 keV). The time-averaged spectrum from T0-1.02 s to T0+10.24 s is best fit by a Band function with Epeak= 388 +/- 13 keV, alpha = -0.62 +/- 0.03 and beta = -2.36 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (5.51 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.28 s in the 10-1000 keV band is 65.9 +/- 0.86 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: 22425 SUBJECT: GRB 180218A CALET Gamma-Ray Burst Monitor detection DATE: 18/02/20 06:02:34 GMT FROM: Takanori Sakamoto at AGU W. Ishizaki (ICRR), A. Yoshida, T. Sakamoto, V. Pal'shin, Y. Kawakubo, M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (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), M. L. Cherry (LSU), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The bright GRB 180218A (Svinkin et al., GCN circ. 22423; Poolakkil et al., GCN circ. 22424) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 15:14:05.326 UTC on 18 February 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows a single multi-peaked pulse which starts at T+0.5 sec, peaks at T+4.6 sec and ends at T+8.5 sec. The T90 and the T50 durations measured by the SGM data are 4.75 +- 1.27 sec and 1.88 +- 0.13 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1203001776/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22426 SUBJECT: Konus-Wind observation of GRB 180218A DATE: 18/02/20 13:20:00 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 180218A (IPN Triangulation: Svinkin et al., GCN 22423; Fermi-GBM detection: Poolakkil et al., GCN 22424; CALET Gamma-Ray Burst Monitor detection: Ishizaki et al., GCN 22425) triggered Konus-Wind at T0=54845.382 s UT (15:14:05.382) The burst light curve shows a single, bright, multi-peaked pulse. The total duration of the burst is ~17 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of (7.6 ± 0.6)x10^-5 erg/cm2 and a 64-ms peak energy flux, measured from T0+3.648, of (3.2 ± 0.3)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+14.080 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.52 (-0.08,+0.09), the high energy photon index beta = -2.27 (-0.15,+0.11), the peak energy Ep = 361 (-31,+33) keV, chi2 = 82/97 dof. The spectrum near the peak count rate (measured from T0 to T0+4.096 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.40 (-0.11,+0.12), the high energy photon index beta = -2.39 (-0.24,+0.16), the peak energy Ep = 384 (-39,+43) keV, chi2 = 88/95 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180218_T54845/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22441 SUBJECT: GRB 180218A: AstroSat CZTI detection DATE: 18/02/24 15:17:31 GMT FROM: Vidushi Sharma at IUCAA V. Sharma (IUCAA), 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 bright GRB 180218A, which was also detected by IPN Triangulation(Svinkin D. et al., GCN 22423), Fermi-GBM (Poolakkil S. et al., GCN 22424), CALET (Ishizaki W. et al., GCN 22425) and Konus-Wind (Frederiks D. et al., GCN 22426). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 15:14:10.5 UT. The measured peak count rate is 1360.5 cts/s above the background in combined data of four quadrants, with a total of 4651 cts. The local mean background count rate was 491.4 cts/s. Using cumulative rates, we measure a T90 of 4.9 s. In Preliminary analysis, we find that 380.4 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.