//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18678 SUBJECT: GRB 151210A: Swift detection of a burst DATE: 15/12/10 03:35:37 GMT FROM: Scott Barthelmy at NASA/GSFC P. A. Evans (U Leicester), S. D. Barthelmy (GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 03:12:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151210A (trigger=666931). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 65.182, -71.230 which is RA(J2000) = 04h 20m 44s Dec(J2000) = -71d 13' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a couple of peaks with a duration of about 60 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~14 sec after the trigger. The XRT began observing the field at 03:15:26.7 UT, 150.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 65.1177, -71.2509 which is equivalent to: RA(J2000) = 04h 20m 28.25s Dec(J2000) = -71d 15' 03.4" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 105 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 consistent with the Galactic value of 1.30 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 150 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 none of the XRT error circle. 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 0.12. Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 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: 18679 SUBJECT: GRB 151210A: Optical afterglow candidate from LCOGT-Cerro Tololo DATE: 15/12/10 05:33:13 GMT FROM: Dong Xu at NAOC/CAS Yanhui Han (NAOC/CAS, HUST), Thomas Kruehler (ESO), Dong Xu (NAOC/CAS), Youdong Hu (IAA-CSIC), and Yin Qing (Geneva Observatory) report: We observed the field of GRB 151210A (Evans et al., GCN 18678) with the 1-m LCOGT telescope at Cerro Tololo, Chile. Observations started 03:34:06 UT on 2015-12-10 (i.e., 21.2 mins after the GRB), and we obtained 10x240s R-band images. Within the XRT error circle (Evans et al., GCN 18678), an uncatalogued optical source is detected in our stacked image at coordinates: R. A. = 04:20:28.048 Dec. = -71:15:02.53 with an error radius of ~0.5 arcsec. The object roughly has R~21.5 mag, calibrated with the nearby USNO B1 field. We thus consider that the source is very likely the optical afterglow of GRB 151220A. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18680 SUBJECT: GRB 151210A: GROND Afterglow Confirmation DATE: 15/12/10 05:39:43 GMT FROM: Alexander Kann at TLS Tautenburg P. Wiseman, T. Kruehler (both MPE Garching), D. A. Kann (TLS Tautenburg), C. Delvaux, and J. Greiner (both MPE Garching) report on behalf of the GROND team: We observed the field of GRB 151210A (Swift trigger 666931; Evans et al., GCN #18678) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 03:17:35 UT on 10/12/2015, 279 sec after the GRB trigger, and are ongoing. We detect a source not seen in the DSS at the edge of the refined XRT error circle (Evans et al., GCN #18678) at: RA (J2000) = 04:20:27.91 Dec. (J2000) = -71:15:02.6 with an error of 0".5 in each coordinate. We suggest that this is the afterglow of the GRB, as we also detect fading between observations. This source is also seen by LCOGT (Han et al., GCN #18679). Based on observations with an integration time of 594 sec (griz) and 540 sec (JHK) centered 54 min after the GRB trigger, we derive magnitudes g' = 23.9 +/- 0.2 mag, r' = 22.1 +/- 0.1 mag, i' = 21.7 +/- 0.1 mag, z' = 21.2 +/- 0.1 mag, J = 20.3 +/- 0.2 mag, and H = 19.8 +/- 0.2 mag. The given limits are derived based on calibrating the images against GROND zero points and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B- V)= 0.11 in the direction of the burst (Schlafly & Finkbeiner 2011). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18681 SUBJECT: GRB 151210A: Enhanced Swift-XRT position DATE: 15/12/10 07:47:44 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1491 s of XRT Photon Counting mode data and 2 UVOT images for GRB 151210A, 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 = 65.11644, -71.25075 which is equivalent to: RA (J2000): 04h 20m 27.95s Dec (J2000): -71d 15' 02.7" 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: 18682 SUBJECT: GRB 151210A: Swift-XRT refined Analysis DATE: 15/12/10 13:01:19 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), T.G.R. Roegiers (PSU), A.P. Beardmore (U. Leicester), S.L. Gibson (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), L.M. McCauley (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.1 ks of XRT data for GRB 151210A (Evans et al. GCN Circ. 18678), from 137 s to 23.7 ks after the BAT trigger. The data comprise 145 s in Windowed Timing (WT) mode (the first 6 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 Beardmore et al. (GCN Circ. 18681). The light curve can be modelled with an initial power-law decay with an index of alpha=5.1 (+0.9, -0.8), followed by a break at T+280 s to an alpha of 0.56 (+/-0.11). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.89 (+0.23, -0.09). The best-fitting absorption column is consistent with the Galactic value of 1.3 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.3 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 1.3 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.89 (+0.23, -0.09) If the light curve continues to decay with a power-law decay index of 0.56, the count rate at T+24 hours will be 9.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.2 x 10^-13 (4.0 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/00666931. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18683 SUBJECT: GRB 151210A: Swift-BAT refined analysis DATE: 15/12/10 14:08:52 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), 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-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 151210A (trigger #666931) (Evans, et al., GCN Circ. 18678). The BAT ground-calculated position is RA, Dec = 65.080, -71.225 deg, which is RA(J2000) = 04h 20m 19.1s Dec(J2000) = -71d 13' 28.9" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 60%. The mask-weighted light curve shows several peaks starting at ~T-55 sec, with the brightest peaks at ~T+14 and ~T+38 sec, and ending at ~T+60sec. T90 (15-350 keV) is 94.9 +- 10.4 sec (estimated error including systematics). The time-averaged spectrum from T-57.19 to T+48.36 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.82 +- 0.79, and Epeak of 49.4 +- 15.3 keV (chi squared 53.7 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+38.82 sec in the 15-150 keV band is 0.8 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.83 +- 0.15 (chi squared 59.89 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/666931/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18684 SUBJECT: GRB 151210A: Swift/UVOT Upper Limits DATE: 15/12/10 15:12:29 GMT FROM: Samantha Oates at MSSL S. R. Oates (IAA-CSIC/UCL-MSSL) and P. A. Evans (U Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151210A 153 s after the BAT trigger (Evans et al., GCN Circ. 18678). No optical afterglow consistent with the optical position (Han et al., GCN Circ. 18679; Wiseman et al. GCN Circ. 18680) 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 153 302 147 >21.1 u_FC 311 560 246 >20.5 white 153 7227 805 >22.1 v 640 7549 442 >20.3 b 566 7023 510 >20.9 u 311 6817 736 >20.8 w1 690 6613 313 >20.4 m2 840 6407 235 >19.8 w2 616 7433 490 >20.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.12 in the direction of the burst (Schlegel et al. 1998).