//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14105 SUBJECT: GRB 121226A: Swift detection of a burst DATE: 12/12/26 19:24:11 GMT FROM: Hans Krimm at NASA-GSFC H. A. Krimm (CRESST/GSFC/USRA), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), S. T. Holland (STScI), K. L. Page (U Leicester), T. Sakamoto (AGU), M. H. Siegel (PSU) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 19:09:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 121226A (trigger=544027). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 168.658, -30.414 which is RA(J2000) = 11h 14m 38s Dec(J2000) = -30d 24' 51" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak with a duration of about 2 sec. The peak count rate was ~2700 counts/sec (15-350 keV), at ~0 sec after the trigger. Although the duration of this burst is moderately short, it has a fairly soft spectrum. Therefore we must wait for further data to determine whether to classify GRB 121226A as a short or long burst. The XRT began observing the field at 19:11:24.4 UT, 100.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 168.6424, -30.4066 which is equivalent to: RA(J2000) = 11h 14m 34.17s Dec(J2000) = -30d 24' 23.8" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 55 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (6.11 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 6.4 (+3.77/-3.06) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 104 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 0.05. Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). 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: 14106 SUBJECT: GRB 121226A: BOOTES-4/MET optical observations DATE: 12/12/26 22:35:11 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia S. Guziy (Mykolaiv Nat. Univ.), O. Lara-Gil, R. Cunniffe, J. Gorosabel, M. Jelinek (IAA-CSIC), P. Kubanek (IP AS CR), Y. Fan, X. Zhao, J. Bai, C. Wang, Y. Xin (Yunnan Nacional Astronomical Observatory), Ch. Cui (Beijing National Astronomical Observatory) and A. J. Castro-Tirado (IAA-CSIC), on behalf of a larger collaboration, report: “Following the detection of GRB 121226A by Swift (Krimm et al. GCNC 14105), the 0.6m BOOTES-4/MET robotic telescope at the Lijiang Astronomical Observatory (China) responded automatically to the trigger alert at 19:10:21 UT, 9 s after the GCN reception (i.e. 36 s after the onset of the event). After initial 0.5 s exposures, the first 19 unfiltered images (5 s exposure time each) starting 6 m 24 s postburst, show no optical afterglow at the refined XRT position down to 19th mag limiting magnitude (for the combined image). Observations are ongoing.” [GCN OPS NOTE(26dec12): Per author's request, "Lara" was changed to "Lara-Gil".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14107 SUBJECT: GRB 121226A: Zadko observatory - Gingin optical observations DATE: 12/12/26 23:18:31 GMT FROM: Alain Klotz at CESR-CNRS A. Klotz (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR), D. Coward (UWA), B. Gendre (ASDC/INAF-OAR), M. Boer (UNS-CNRS-OCA), A. Williams (PO-UWA), R. Martin (PO-UWA) report: We imaged the field of GRB 121226A detected by SWIFT (trigger 544027) with the Zadko robotic telescope (D=100cm) located at the observatory - Gingin, Australia. The observations started 62.8s after the GRB trigger (38.6s after the notice). The elevation of the field increased from 64 degrees above horizon and weather conditions were good. The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT in the XRT error box with a limiting magnitude of: t0+62.8s to t0+122.8s : Rlim 17.5 The second image is 30.0s exposure in tracking mode: t0+138s to t0+168s : Rlim 18.7 We co-added a series of exposures: t0+138s to t0+335s : Rlim 19.4 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14108 SUBJECT: GRB 121226A: MITSuME Okayama Optical upper limits DATE: 12/12/26 23:55:05 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 the MITSuME collaboration: We observed the field of GRB 121226A (Krimm et al., GCNC 14105) 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 2012-12-26 19:11:59 UT (~2.3 min after the burst). We did not find any new point source within the XRT circle (Krimm et al., GCNC 14105) 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 ------------------------------------------------------ 0.04333 20:12:06 6360.0 >20.2 >20.2 >19.5 ------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14109 SUBJECT: GRB 121226A: Optical Observations DATE: 12/12/27 07:29:30 GMT FROM: Shashi Bhushan Pandey at ROTSE V.K. Bhatt, S.B. Pandey and Brajesh Kumar ((ARIES Nainital, India, on behalf of larger Indian GRB collaboration) We observed GRB 121226A (Swift trigger 518731, Krimm et al. 2012, GCNC 14105) field with the 1.04m telescope at ARIES, Nainital starting at 2012-12-26 21:09:09 (UT). Several frames in R_c and I_c pass-bands, with an exposure time of 300 sec each, were obtained. Within the XRT error-circle, we do not detect any optical source down to following limiting magnitudes. Dec 26.9118 UT, 300sx4, I_c ~ 18.8 mag Dec 26.9292 UT, 300sx6, R_c ~ 19.5 mag The nearby USNO stars have been used for calibrate. This massage may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14110 SUBJECT: GRB 121226A: NOT optical upper limit DATE: 12/12/27 07:46:12 GMT FROM: Dong Xu at DARK/NBI D. Xu (DARK/NBI), O. Smirnova, T. Purismo (NOT), J. P. U. Fynbo (DARK/NBI), P. Jakobsson (U. Iceland) report on behalf of a larger collaboration: We observed the field of GRB 121226A (Krimm et al., GCN 14105) using the 2.5m Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained 3x600s R-band and 3x360s z-band images with their median time of 06:14:49 UT on 2012-12-27 (i.e., 11.085 hr after the BAT trigger) and 06:53:54 UT (i.e., 11.736 hr post-trigger), respectively. No optical source was detected within the XRT error circle in both R-and z-bands, down to a 3sigma limit of R~23.0 mag ,calibrated with the USNO B1 catalogue. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14111 SUBJECT: GRB 121226A, Swift-BAT refined analysis DATE: 12/12/27 14:27:06 GMT FROM: Hans Krimm at NASA-GSFC W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-61 to T+111 sec from the recent telemetry downlink, we report further analysis of BAT GRB 121226A (trigger #544027) (Krimm, et al., GCN Circ. 14105). The BAT ground-calculated position is RA, Dec = 168.620, -30.413 deg which is RA(J2000) = 11h 14m 28.7s Dec(J2000) = -30d 24' 47.0" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%. The mask-weighted light curve shows a single peak with duration approximately 1.5 seconds, with no sign of extended emission. T90 (15-350 keV) is 1.00 +- 0.20 sec (estimated error including systematics). The time-averaged spectrum from T-0.36 to T+0.80 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.51 +- 0.29. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.21 sec in the 15-150 keV band is 1.6 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. When plotting GRB 121226A on the T90-hardness diagram (see web link below), we see that it falls within the short-hard region of phase space, with T90 = 1.0 sec and Hardness ratio (energy fluence ratio 50-100 keV/25-50 keV) = 1.4. Therefore we now suggest that GRB 121226A should be classified as a short-hard burst. We do not have a lag analysis available at this time. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/544027/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14112 SUBJECT: GRB 121226A: Swift-XRT refined Analysis DATE: 12/12/27 18:24:04 GMT FROM: Phil Evans at U of Leicester O.M. Littlejohns (U. Leicester), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and H.A. Krimm report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 121226A (Krimm et al. GCN Circ. 14105), from 109 s to 35.4 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The best available XRT position (using the promptly downlinked event data, the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 168.6423, -30.4064 which is equivalent to: RA (J2000): 11 14 34.14 Dec(J2000): -30 24 23.1 with an uncertainty of 2.1 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=0.98 (+/-0.06). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.4 (+/-0.4). The best-fitting absorption column is 8.2 (+2.5, -2.1) x 10^21 cm^-2, in excess of the Galactic value of 6.1 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (1.2 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 8.2 (+2.5, -2.1) x 10^21 cm^-2 Galactic foreground: 6.1 x 10^20 cm^-2 Excess significance: 6.0 sigma Photon index: 2.4 (+/-0.4) If the light curve continues to decay with a power-law decay index of 0.98, the count rate at T+24 hours will be 1.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.7 x 10^-14 (1.9 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00544027. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14113 SUBJECT: GRB 121226A: Swift/UVOT Upper Limits DATE: 12/12/27 21:17:57 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (MSSL-UCL) and H. A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 121226A 104 s after the BAT trigger (Krimm et al., GCN Circ. 14105). No optical afterglow consistent with the XRT position (Littlejohns et al. GCN Circ. 14112) 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 104 254 147 >20.6 u_FC 317 566 246 >19.6 white 104 18160 1317 >21.6 v 646 10716 1121 >20.4 b 572 17397 1317 >21.3 u 317 16485 1544 >20.9 w1 696 12390 1163 >20.7 m2 671 11621 1298 >21.0 w2 622 6620 351 >20.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.055 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14114 SUBJECT: GRB 121226A: 10.4m GTC optical observations DATE: 12/12/28 01:49:33 GMT FROM: Javier Gorosabel at IAA-CSIC A.J. Castro-Tirado, M. Jelinek, R. Sánchez-Ramírez, J.C. Tello (IAA-CSIC), J.M. González-Pérez (GTC/IAC), S. Guziy (Mykolaiv Nat. Univ.), D. Pérez-Ramírez (Univ. de Jaén), P. Ferrero (IAC), J.M. Castro Cerón (ESAC), A. Fernández-Soto (IFCA-UNICAN) and J. Gorosabel (IAA-CSIC), report: “We have obtained deep r’i’z’ images with the 10.4m GTC telescope at Observatorio del Roque de los Muchachos for GRB 121226A (Krimm et al. GCNC 14105; Baumgartner et al. GCNC 14111) starting on Dec 27.230--27.261 UT (i.e., 10.3--11.1 hr post burst). A faint object is detected at RA(J2000)=11:14:34.14, DEC(J2000)=-30:24:22.9 (0.7" error in each coordinate), consistent with the position of the X-ray afterglow (Littlejohns et al. GCNC 14112). The object shows a magnitude around r'~25. At this stage we cannot conclude whether this is the GRB 121226A optical afterglow or the underlying host galaxy.” //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14126 SUBJECT: GRB 121226A: 5.8 GHz VLA observations DATE: 12/12/30 17:26:03 GMT FROM: Wen-fai Fong at CFA W. Fong, B. A. Zauderer and E. Berger (Harvard) report: "We observed the position of the short-duration GRB 121226A (Krimm et al., GCN 14105; Baumgartner et al. GCN 14111) with the Karl G. Jansky Very Large Array (VLA) beginning on 2012 December 28.54 UT (1.75 days post-burst) at a mean frequency of 5.8 GHz. In 35-min on source, we detect a faint, 3-sigma radio source at: RA (J2000) = 11:14:34.12 DEC (J2000) = -30:24:22.89 with an uncertainty of ~0.2" in each coordinate. This position is coincident with the XRT and optical positions (Littlejohns et al., GCN 14112; Castro-Tirado et al., GCN 14114). Further observations are planned." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 14139 SUBJECT: Short GRB 121226A: TNG observation of the host galaxy DATE: 13/01/14 22:19:49 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK/NBI), P. D'Avanzo (INAF/OABr), A. Melandri (INAF/OABr), S. Covino (INAF/OABr), A. Fiorenzano (INAF/TNG), L. Di Fabrizio (INAF/TNG), and G. Andreuzzi (INAF/TNG) report on behalf of the CIBO collaboration: We observed the optical counterpart (Castro-Tirado et al., GCN 14114) of the short GRB 121226A (Krimm et al., GCN 14105) with the TNG telescope located in the Canary Islands. A total two hour exposure in the SDSS r filter was acquired, with mean time 2013 Jan 11.227 UT (15.4 days after the GRB). Sky conditions were good and the seeing was 1.1", despite the large airmass (around 2). Consistent with the position reported by Castro-Tirado et al. (GCN 14114) and Fong et al. (GCN 14126), we clearly detect an object with r(AB) = 24.68 +- 0.15. Photometric calibration was carried out by observing a standard field at similar airmass (for reference, we find r = 19.35 for the USNO star at RA = 11:14:33.12, Dec = -30:23:51.2). Coupled with the measurement by Castro-Tirado et al. (GCN 14114), obtained ~0.5 days after the GRB, our observation suggests that the object is the host galaxy of the GRB, with negligible afterglow contribution at both epochs. We note that the radio detection (Fong et al., GCN 14126) makes the association with the GRB secure. The coordinates of the object as measured in our image are (J2000, astrometry calibrated against USNO-B1): RA = 11:14:34.125 Dec = -30:24:22.88 with an estimated uncertainty of 0.3". We note the presence of two further, nearby objects, roughly 2" S and 4" NE of the optical/radio counterpart. A finding chart is available at the following URL: http://www.astro.ku.dk/~malesani/GRB/121226A/GRB121226A_finder_TNG.jpg