//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12256 SUBJECT: GRB 110808A: Swift detection of a burst with optical counterpart DATE: 11/08/08 06:36:32 GMT FROM: Giulia Stratta at ASDC G. Stratta (ASDC), W. H. Baumgartner (GSFC/UMBC), M. M. Chester (PSU), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), A. Melandri (INAF-OAB), K. L. Page (U Leicester) and C. J. Saxton (UCL-MSSL) report on behalf of the Swift Team: At 06:18:54 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110808A (trigger=458918). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 57.264, -44.179 which is RA(J2000) = 03h 49m 03s Dec(J2000) = -44d 10' 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 10 sec. The peak count rate was ~400 counts/sec (15-350 keV), at ~4 sec after the trigger. The XRT began observing the field at 06:20:45.1 UT, 110.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 57.2666, -44.1944 which is equivalent to: RA(J2000) = 03h 49m 3.97s Dec(J2000) = -44d 11' 40.0" with an uncertainty of 2.6 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.04 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 3 (+3.41/-2.82) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 5.42e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 120 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 03:49:04.28 = 57.26782 DEC(J2000) = -44:11:40.3 = -44.19452 with a 90%-confidence error radius of about 0.83 arc sec. This position is 5.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.93 with a 1-sigma error of about 0.19. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. Burst Advocate for this burst is G. Stratta (giulia.stratta AT asdc.asi.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: 12257 SUBJECT: GRB 110808A: Enhanced Swift-XRT position DATE: 11/08/08 10:56:19 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 304 s of XRT Photon Counting mode data and 1 UVOT images for GRB 110808A, 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 = 57.26664, -44.19536 which is equivalent to: RA (J2000): 03h 49m 3.99s Dec (J2000): -44d 11' 43.3" with an uncertainty of 3.2 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: 12258 SUBJECT: GRB 110808A: VLT/X-shooter spectroscopy DATE: 11/08/08 11:04:03 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo, J. P. U. Fynbo (DARK/NBI), P. Jakobsson (U. Iceland), B. Milvang-Jensen (ESO, DARK/NBI), A. Melandri (INAF-OABr), D. Malesani (DARK/NBI), S. Schulze (U. Iceland), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), N. R. Tanvir (U. Leicester), H. Flores (Paris Obs.), K. Wiersema (U. Leicester), S. Covino (INAF-OABr), L. Lovisi, B. Lanzoni (U. Bologna) report on behalf of the X-shooter GRB collaboration: We observed the afterglow of GRB 110808A (Stratta et al. GCN 12256) with the ESO VLT equipped with the X-shooter spectrograph on 8 August 2011, beginning 09:19 UT (3 hr after the GRB). The acquisition image shows the UVOT optical afterglow candidate to have R ~ 21.2 mag. We detect several emission lines, including [O II], [O III] and H-alpha at a common redshift of z = 1.348 (based on archival calibration frames). At the same redshift we detect the Mg II doublet and Fe transitions in absorption. We acknowledge the support of the VLT staff, in particular Claudio Melo. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12261 SUBJECT: GRB 110808A: Swift-XRT refined Analysis DATE: 11/08/08 14:49:07 GMT FROM: Giulia Stratta at ASDC G. Stratta and V. D'Elia (ASDC) report on behalf of the Swift-XRT team: We have analysed 3.8 ks of XRT data for GRB 110808A (Stratta et al. GCN Circ. 12256), from 100 s to 18.0 ks after the BAT trigger. The data comprise 91 s in Windowed Timing (WT) mode (the first 9 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 Goad et al. (GCN. Circ 12257). The light curve can be modelled with an initial power-law decay with an index of alpha=3.79 (+0.22, -0.20), followed by a break at T+459 s to an alpha of 0.57 (+0.18, -0.23). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 3.07 (+0.29, -0.25). The best-fitting absorption column is 2.9 (+1.4, -1.3) x 10^21 cm^-2, at a redshift of 1.348 (de Ugarte Postigo et al. GCN Circ. 12258), in addition to the Galactic value of 1.0 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 2.2 x 10^-11 (3.5 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Galactic foreground: 1.0 x 10^20 cm^-2 Intrinsic column: 2.9 (+1.4, -1.3) x 10^21 cm^-2 at z=1.348 Photon index: 3.07 (+0.29, -0.25) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00458918. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12262 SUBJECT: GRB 110808A: Swift-BAT refined analysis DATE: 11/08/08 14:51:05 GMT FROM: Scott Barthelmy at NASA/GSFC T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (OSU), G. Stratta (ASDC), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-471 to T+639 sec from recent telemetry downlinks, we report further analysis of BAT GRB 110808A (trigger #458918) (Stratta, et al., GCN Circ. 12256). The BAT ground-calculated position is RA, Dec = 57.322, -44.177 deg which is RA(J2000) = 03h 49m 17.2s Dec(J2000) = -44d 10' 35.4" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 76%. The mask-weighted light curve shows a FRED pulse shape starting at ~T+0 sec, peaking at ~T+1 sec, and returning the baseline at ~T+50 sec. T90 (15-350 keV) is 48 +- 23 sec (estimated error including systematics). The time-averaged spectrum from T-7.4 to T+40.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.32 +- 0.43. The fluence in the 15-150 keV band is 3.3 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band is 0.4 +- 0.2 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/458918/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12264 SUBJECT: GRB 110808A: Swift/UVOT Detection DATE: 11/08/08 19:04:03 GMT FROM: Tyler Pritchard at PSU T. A. Pritchard (PSU) and G. Stratta (ASDC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 110808A 120 s after the BAT trigger (Stratta et al., GCN Circ. 12256). A source consistent with the Enhanced Swift-XRT position (Goad et al., GCN Circ. 12257) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 03:49:04.27 = 57.26780 (deg.) Dec (J2000) = -44:11:40.1 = -44.19448 (deg.) with an estimated uncertainty of 0.64 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 120 270 147 19.88 ± 0.14 white 57 559 19 18.48 ± 0.23 white 3996 4196 200 20.17 ± 0.16 v 609 629 19 >18.7 b 535 555 20 18.64 ± 0.32 u 279 528 246 18.28 ± 0.09 u 683 703 19 17.48 ± 0.25 u 6062 6262 196 >20.62 w1 658 678 19 >17.8 w2 585 605 19 >18.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12269 SUBJECT: IPN triangulation of GRB 110808B (short/hard/intense) DATE: 11/08/10 21:29:44 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team, I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team, W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, and D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, and W. Hajdas, on behalf of the RHESSI GRB team, report: GRB 110808B, a very intense short-duration, hard spectrum GRB, was observed by Konus-Wind, Mars Odyssey, MESSENGER, and RHESSI at 56693 s UT. We have triangulated it to a preliminary, 3 sigma error box whose area is about 108 square arcminutes, whose maximum dimension is ~22 arcminutes, and whose coordinates are: RA(2000) Dec(2000) CENTER: 266.1808=17 h 44 m 43.4 s -37.7463=-37 o 44 ' 47 " CORNERS: 266.0492=17 h 44 m 11.8 s -37.7586=-37 o 45 ' 31 " 266.3453=17 h 45 m 22.9 s -37.8732=-37 o 52 ' 24 " 266.0166=17 h 44 m 04.0 s -37.6169=-37 o 37 ' 01 " 266.3123=17 h 45 m 14.9 s -37.7332=-37 o 44 ' 00 " Although this error box lies at Galactic latitude -5 degrees, it does not include any of the known magnetars. A Swift ToO has been requested. Further details of the spectrum and time history will appear in a forthcoming GCN Circular. A map is posted at ssl.berkeley.edu/ipn3/110808B. This error box can be improved. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12271 SUBJECT: Konus-Wind observation of GRB 110808B DATE: 11/08/11 11:15:57 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The short-duration extremely hard GRB 110808B (localized by IPN: Hurley et al., GCN 12269) triggered Konus-Wind at T0=56695.237s UT (15:44:55.237) The burst light curve shows a single bright hard pulse, with a duration of ~0.5 s and much weaker tail of the emission which is detectable till T0+8 s. The emission is seen up to 13 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB110808_T56695/ As observed by Konus-Wind the burst had a fluence of (1.6 ± 0.2)x10-5 erg/cm2, and a 16-ms peak flux, measured from T0+0.112 s, of (1.1 ± 0.2)x10-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The spectrum of the burst (measured from T0 to T0+0.256 s) is best fitted in the 20 keV - 10 MeV range by a power law with exponential cutoff model, for which alpha = -1.13 (-0.08, +0.08), and Ep = 2960(-796, +1217) keV, chi2 = 53.2/45 dof. Fitting this spectrum by the GRB (Band) function yields the following model parameters: the low-energy photon index alpha = -1.13 (-0.08, +0.07), the high energy photon index beta = -2.5 (<-1.9), the peak energy Ep = 2630(-744, +836) keV, chi2 = 54.3/44 dof. The spectrum at the maximum count rate (measured from T0+0.064 to T0+0.128 s) is best fitted in the 20 keV - 10 MeV range by a power law with exponential cutoff model, for which alpha = -1.07 (-0.11, +0.12), and Ep = 4238(-1530, +3270) keV, chi2 = 12.5/16 dof. All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.