//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20283 SUBJECT: GRB 161218A: Swift detection of a burst DATE: 16/12/18 04:01:36 GMT FROM: David Palmer at LANL A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), H. A. Krimm (CRESST/NSF/USRA), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 03:47:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 161218A (trigger=727288). Swift could not slew to the burst do to an observing constraint. The BAT on-board calculated location is RA, Dec 245.257, -4.114 which is RA(J2000) = 16h 21m 02s Dec(J2000) = -04d 06' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single complex structure with a duration of about 10 sec. The peak count rate was ~20000 counts/sec (15-350 keV), at ~1 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 15:54 UT on 2017 January 08. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is A. D'Ai (antonino.dai AT ifc.inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20287 SUBJECT: GRB 161218A: POLAR observation DATE: 16/12/18 18:58:48 GMT FROM: Zhengheng Li at POLAR Z. H. Li (IHEP), Y. H. Wang (IHEP), S. L. Xiong (IHEP) report for the POLAR collaboration: At 2016-12-18T03:47:34.634 UT (T0), during a routine on-ground  search of data, POLAR detected the GRB 161218A,  which was also detected by the Swift/BAT (trigger #727288). The POLAR light curve consists of a single peak, with a duration (T90) of 6.76 s measured from T0+0.25 s . The 0.25s peak rate measured from T0+1.25 s is 2660 cnts/s, The total counts is about 6644 cnts. The above measurements are in the energy range of about 80-500 keV. The preliminary estimation of minimum detectable polarization (MDP) is 32.5%[3-sigma, statistical only]. Follow-up observations are strongly encouraged. LC_URL: http://polar.ihep.ac.cn/grb/2016/GRB161218A/lc/POLAR_lc_grb161218158.png Using the best location from the Fermi/GBM, which is (J2000): RA:    245.257   [deg] Dec:   -4.114   [deg] Err:     3.00 [arcmin] the incident angle in POLAR coordinate at T0 is: theta:  24.327  [deg] phi:   356.614  [deg] The analysis results presented above are preliminary. POLAR is a dedicated Gamma-Ray Burst polarimeter (50-500 keV) on-board the Chinese space laboratory Tiangong-2 launched on Sep 15, 2016. More information about POLAR can be found at http://polar.ihep.ac.cn/en/ , http://isdc.unige.ch/polar/ and http://polar.psi.ch/html/ . //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20290 SUBJECT: GRB 161218A: TAROT Calern observatory optical observations DATE: 16/12/18 20:58:27 GMT FROM: Alain Klotz at IRAP-CNRS-OMP Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Laugier, R. (CNRS-ARTEMIS), Gendre B. (UVI - Etelman Obs.) report: We imaged the field of GRB 161218A detected by SWIFT (trigger 727288) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 49 min after the GRB trigger at the end of the night. The elevation of the field increased from 3 degrees above horizon and weather conditions were good. We co-added a series of exposures. We do not detect any OT with a limiting magnitude of: t0+49 min to t0+68 min : Rlim = 17.3 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20292 SUBJECT: Konus-Wind observation of GRB 161218A DATE: 16/12/19 12:03:31 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 161218A (Swift-BAT detection: D'Ai et al., GCN 20283; POLAR observation: Li et al., GCN 20287) triggered Konus-Wind at T0=13651.970 s UT (03:47:31.970). The burst light curve shows a single pulse with a total duration of ~7 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of (1.24 ± 0.10)x10^-5 erg/cm2 and a 64-ms peak energy flux, measured from T0+0.640, of (4.6 ± 0.4)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+10.496 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 = -0.28 (-0.21,+0.25), the high energy photon index beta = -3.40 (-1.17,+0.43), the peak energy Ep = 128 (-8,+8) keV, chi2 = 110/97 dof. The spectrum near the peak count rate (measured from T0+0.256 to T0+2.304 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 = +0.08 (-0.26,+0.29), the high energy photon index beta = -3.18 (-0.59,+0.31), the peak energy Ep = 135 (-9,+10) keV, chi2 = 84/74 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB161218_T13651/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20293 SUBJECT: GRB 161218A: Swift-BAT refined analysis DATE: 16/12/19 13:48:29 GMT FROM: Takanori Sakamoto at AGU C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA), N. Gehrels (GSFC),H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-352 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 161218A (trigger #727288) (D'Ai, et al., GCN Circ. 20283). The BAT ground-calculated position is RA, Dec = 245.250, -4.113 deg which is RA(J2000) = 16h 21m 00.1s Dec(J2000) = -04d 06' 46.3" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 60%. The mask-weighted light curve shows a bright FRED-like peak starting from T-2 sec, peaking at T+1 sec and ending at T+14 sec. A possible extended emission is evident in the 10-sec binning light curve lasting until T+80 sec. T90 (15-350 keV) is 7.1 +- 0.6 sec (estimated error including systematics). The time-averaged spectrum from T-1.4 to T+14.5 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.56 +- 0.16, and Epeak of 117 +- 13 keV (chi squared 38.16 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 6.7 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+0.27 sec in the 15-150 keV band is 17.6 +- 0.5 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.29 +- 0.03 (chi squared 111.22 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/727288/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20294 SUBJECT: GRB 161218A: CALET Gamma-Ray Burst Monitor detection DATE: 16/12/19 13:57:59 GMT FROM: Takanori Sakamoto at AGU S. Torii (Waseda U), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration: The long-duration GRB 161218A (D'Ai et al., GCN Circ. 20283) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 03:47:31.89 on 18 December 2016. No real time CGBM GCN notice was distributed about this trigger because the real time communication from the ISS was off (loss of signal) between 3:43 and 3:52. The burst signal was seen by all CGBM instruments. The light curve of the SGM shows a FRED-like structure starting at T+3 sec, peaking at T+5 sec and ending at T+10 sec. The T90 duration measured by the SGM data is 5.1 +- 0.2 sec (40-1000 keV). The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1166067870/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.