//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22288 SUBJECT: GRB 171227A: AGILE/MCAL detection DATE: 17/12/27 18:34:44 GMT FROM: Francesco Verrecchia at ASDC F. Verrecchia (SSDC and INAF/OAR), A.Ursi (INAF/IAPS), A. Trois (INAF/OA-Cagliari), C. Pittori (SSDC and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Marisaldi (INAF/IASF-Bo and Bergen University), N. Parmiggiani (INAF/IASF-Bo), F. Longo (Univ. Trieste and INFN Trieste), A. Bulgarelli (INAF/IASF-Bo), M. Cardillo, M. Pilia (INAF/OA-Cagliari), G. Piano (INAF/IAPS), I. Donnarumma (ASI), G. Minervini, A. Argan, Y. Evangelista (INAF/IAPS), F. Lucarelli (SSDC and INAF/OAR), V. Fioretti, F. Fuschino (INAF/IASF-Bo), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team: The AGILE Mini-CALorimeter (MCAL) detected a long burst at T0 = 2017-12-27 00:00:30.00 +/- 0.01 UTC in the acquired data interval (following an internal trigger) started at T1=00:00:29.00 UTC and ended at 00:00:46.50 UTC. The MCAL light curve shows a multi-peaked structure, with the main part within T0+0.70 s and T0+5.50 s and a second short peak at T0+10.50 s. The main GRB interval released a total number of ~28190 counts at E>400 keV in the detector, above an average background rate of 23 counts/32ms. The AGILE-MCAL detector has a full solid angle acceptance, and is operational in the range 0.4 - 100 MeV. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22289 SUBJECT: GRB 171227A: Fermi GBM detection DATE: 17/12/27 18:55:27 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM C. M. Hui (NASA/MSFC) reports on behalf of the Fermi GBM Team: At 00:00:13.40 UT on 27 December 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 171227A (trigger 536025618/171227000), also detected by AGILE/MCAL (Verrecchia et al. GCN 22288). The on-ground calculated location, using the GBM trigger data, is RA = 280.7 , DEC = -35.0 (J2000 degrees, equivalent to 18h 42m, -35d 0.0'), with an uncertainty of 1.0 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 with a systematic error of more than 10 deg [Connaughton et al. 2015, ApJS, 216, 32] ). The angle from the Fermi LAT boresight is 120 degrees. The GBM light curve shows several peaks with decreasing amplitudes and a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0+0.0 s to T0+58.2 s is adequately fit by a Band function with Epeak = 771 +/- 14 keV, alpha = -0.87 +/- 0.01, and beta = -2.47 +/- 0.04. The event fluence (10-1000 keV) in this time interval is (305.3 +/- 1.3) E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+19.4 s in the 10-1000 keV band is 90.3 +/- 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: 22290 SUBJECT: IPN Triangulation of GRB 171227A DATE: 17/12/28 15:01:10 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin, 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, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and G. Di Cocco, F. Fuschino, M. Galli, C. Labanti, M. Marisaldi, and A. Ursi on behalf of the AGILE MCAL team, report: The long-duration GRB 171227A (AGILE-MCAL detection: Verrecchia et al., GCN Circ. 22288, Fermi-GBM observation: Hui et al., GCN Circ. 22289) was detected by Konus-Wind, Fermi (GBM trigger 536025618), INTEGRAL (SPI-ACS), and AGILE (MCAL) at about 13 s UT (00:00:13). We have triangulated it to a preliminary, 3-sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 290.998 (19h 24m 00s) -47.012 (-47d 00' 43") Corners: 295.738 (19h 42m 57s) -48.264 (-48d 15' 50") 284.827 (18h 59m 19s) -46.296 (-46d 17' 44") 287.178 (19h 08m 43s) -45.288 (-45d 17' 16") 298.814 (19h 55m 15s) -46.606 (-46d 36' 22") --------------------------------------------- The error box area is 12.8 sq. deg, and its maximum dimension is 9.6 deg (the minimum one is 96.7 arcmin). The Sun distance was 24 deg. This box may be improved. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB171227_T00009/IPN The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22291 SUBJECT: Konus-Wind observation of GRB 171227A DATE: 17/12/29 13:52:39 GMT FROM: Anastasia Tsvetkova at Ioffe Institute A. Tsvetkova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Lysenko, A.Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, hard-spectrum, very intense GRB 171227A (AGILE/MCAL detection: Verrecchia et al., GCN 22288; Fermi GBM detection: Hui, GCN 22289; IPN Triangulation: Kozlova et al., GCN 22290) triggered Konus-Wind at T0=9.491 s UT (00:00:09.491). The burst light curve shows a multi-peaked structure with a total duration of ~56 s. The emission is seen up to ~19 MeV. As observed by Konus-Wind, the burst had a fluence of 6.31(-0.19,+0.19)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+18.880 s, of 1.19(-0.10,+0.10)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+60.416 s) is best fit in the 20 keV - 19 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.87(-0.03,+0.03), the high energy photon index beta = -2.12(-0.06,+0.05), the peak energy Ep = 618(-35,+38) keV (chi2 = 139/97 dof) The spectrum near the maximum count rate (measured from T0+18.176 to T0+18.944 s) is best fit in the 50 keV - 19 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.77(-0.07,+0.08), the high energy photon index beta = -2.38(-0.26,+0.16), the peak energy Ep = 1498(-215,+262) keV (chi2 = 62/73 dof) The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB171227_T00009/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22313 SUBJECT: GRB 171227A: AstroSat CZTI detection DATE: 18/01/10 09:49:08 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 bright GRB 171227A, which was also detected by AGILE/MCAL (Verrecchia F. et al., GCN 22288), Fermi-GBM (Hui C. M. et al., GCN 22289), IPN Triangulation (Kozlova A. et al., GCN 22290) and Konus-Wind (Tsvetkova A. et al., GCN 22291). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 00:00:32.500 UT, ~19 s after the Fermi-GBM trigger. The measured peak count rate is 2066.8 cts/s above the background in combined data of four quadrants, with a total of 15305 cts. The local mean background count rate was 471 cts/s. Using cumulative rates, we measure a T90 of 25.4 s. 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.