//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18745 SUBJECT: GRB 151229A: Swift detection of a short burst DATE: 15/12/29 07:09:40 GMT FROM: Kim Page at U.of Leicester D. Kocevski (NASA/GSFC/ORAU), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and T. N. Ukwatta (LANL) report on behalf of the Swift Team: At 06:50:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151229A (trigger=668689). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 329.380, -20.729 which is RA(J2000) = 21h 57m 31s Dec(J2000) = -20d 43' 42" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 1.5 sec. The peak count rate was ~7000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 06:51:54.9 UT, 86.9 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 329.3703, -20.7325 which is equivalent to: RA(J2000) = 21h 57m 28.87s Dec(J2000) = -20d 43' 56.9" with an uncertainty of 2.0 arcseconds (radius, 90% containment). This location is 35 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (2.71 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 7.6 (+2.59/-2.28) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 90 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is D. Kocevski (dankocevski AT gmail.com). 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: 18750 SUBJECT: GRB 151229A: Enhanced Swift-XRT position DATE: 15/12/29 10:17:20 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 609 s of XRT Photon Counting mode data and 1 UVOT images for GRB 151229A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 329.36981, -20.73203 which is equivalent to: RA (J2000): 21h 57m 28.76s Dec (J2000): -20d 43' 55.3" with an uncertainty of 1.8 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18751 SUBJECT: GRB 151229A: Swift-BAT refined analysis DATE: 15/12/29 14:19:16 GMT FROM: Scott Barthelmy at NASA/GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), D. Kocevski (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), 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-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 151229A (trigger #668689) (Kocevski, et al., GCN Circ. 18745). The BAT ground-calculated position is RA, Dec = 329.363, -20.732 deg, which is RA(J2000) = 21h 57m 27.1s Dec(J2000) = -20d 43' 56.2" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 51%. The mask-weighted light curve shows single peak starting at ~T-0.1 sec, peaking at ~T+0.1 sec, and ending at ~T+1.7 sec. T90 (15-350 keV) is 1.78 +- 0.44 sec (estimated error including systematics). The time-averaged spectrum from T-0.11 to T+2.34 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.84 +- 0.10. The fluence in the 15-150 keV band is 5.9 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band is 7.2 +- 0.4 ph/cm2/sec. 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/668689/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18753 SUBJECT: GRB 151229A: Swift/UVOT observations DATE: 15/12/29 14:37:16 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151229A 90 s after the BAT trigger (Kocevski et al., GCN Circ. 18745). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 18750) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 90 240 147 >20.0 u_FC 302 552 246 >19.3 white 90 5493 378 >20.5 v 632 5904 413 >18.8 b 558 5288 236 >19.5 u 302 6513 653 >19.8 w1 681 6314 413 >19.7 m2 4474 6108 393 >19.9 w2 4064 5699 393 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998). -- Dr. Massimiliano De Pasquale Research associate - Swift UVOT scientist Mullard Space Science Laboratory, University College London //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18756 SUBJECT: GRB 151229A: Fermi GBM observation DATE: 15/12/29 17:07:57 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 06:50:27.95 UT on 29 December 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 151229A (trigger 473064631 / 151229285 ), which was also detected by the Swift/BAT (Kocevski et al. 2015, GCN 18745) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 53.4 degrees. The GBM light curve consists of a single peak with a duration (T90) of about 3.5 s (50-300 keV). The time-averaged spectrum from T0-0.256: s to T0+1.280 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.19 (+0.10/-0.09) and the cutoff energy, parameterized as Epeak, is 97.1 (+10.3/-8.3) keV The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.5)E-07 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0-0.128 s in the 10-1000 keV band is 11.0 +/- 0.3 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: 18757 SUBJECT: GRB 151229A: Swift-XRT refined Analysis DATE: 15/12/29 20:52:00 GMT FROM: Phil Evans at U of Leicester K.L. Page (U. Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester) and D. Kocevski report on behalf of the Swift-XRT team: We have analysed 7.4 ks of XRT data for GRB 151229A (Kocevski et al. GCN Circ. 18745), from 73 s to 32.8 ks after the BAT trigger. The data comprise 67 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 18750). The light curve can be modelled with a power-law decay with a decay index of alpha=0.832 (+/-0.021). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.04 (+0.15, -0.14). The best-fitting absorption column is 7.2 (+1.1, -1.0) x 10^21 cm^-2, in excess of the Galactic value of 2.7 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (7.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.2 (+1.1, -1.0) x 10^21 cm^-2 Galactic foreground: 2.7 x 10^20 cm^-2 Excess significance: 11.4 sigma Photon index: 2.04 (+0.15, -0.14) If the light curve continues to decay with a power-law decay index of 0.832, the count rate at T+24 hours will be 0.023 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.8 x 10^-13 (1.8 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00668689. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18760 SUBJECT: GRB 151229A Swift-BAT Spectral lag analysis DATE: 15/12/29 23:11:56 GMT FROM: Scott Barthelmy at NASA/GSFC J. Norris (BSU), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC) for the Swift-BAT Team: We report the spectral lag analysis for GRB 151229A (Kocevski, et al., GCN Circ. 18745, & Lien 18751) based on the BAT data. Using 8-ms binned light curve, the spectral lag for the 25-50 keV to 100-300 keV bands is -47.6 +/-31 ms and +12 +/-24 for the 15-25 to 50-100 bands. Although the errors are large, the values are marginally consistent with zero, therefore we believe this burst belongs to a short burst category, although we can not rule out the long burst possibility. There is no evidence for extended emission. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18761 SUBJECT: GRB 151229A: MITSuME Okayama upper limits DATE: 15/12/30 00:02:58 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of MITSuME and OISTER collaboration: We observed the field of GRB 151229A (Kocevski et al., GCNC 18745) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2015-12-29 09:07:26 UT (~2.3h after the burst). We did not find any new point source within the enhanced XRT circle (Osborne et al., GCNC 18750) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' Rc Ic ----------------------------------------------------- 0.11774 09:39:59 2940.0 >18.7 >18.7 >18.2 ----------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18765 SUBJECT: GRB 151229A: MITSuME Akeno optical upper limits DATE: 15/12/30 07:08:42 GMT FROM: Taketoshi Yoshii at Tokyo Tech Y.Saito, T.Fujiwara, T. Yoshii, Y. Tano, Y. Tachibana, Y.Ono, S.Harita, Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 151229A (D. Kocevski et al., GCN Circular #18745) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2015-12-29 08:56:00 UT (~2.1 h after the burst). We did not find any new point source within XRT circle in all three bands. We obtained following limits for the magnitudes. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------- 7533 09:20:52 2700 > 19.5 > 19.4 > 18.6 ------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.