//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10130 SUBJECT: GRB 091104: Swift detection of a burst DATE: 09/11/04 09:08:23 GMT FROM: David Palmer at LANL P.A. Curran (MSSL-UCL), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), S. Campana (INAF-OAB), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), J. A. Kennea (PSU), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), A. Rowlinson (U Leicester) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 08:49:22 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091104 (trigger=374875). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 208.742, +47.398 which is RA(J2000) = 13h 54m 58s Dec(J2000) = +47d 23' 55" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is usual for an image trigger, there is no obvious variation in the immediately available light curve. The XRT began observing the field at 08:51:34.2 UT, 131.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 208.75600, 47.41126 which is equivalent to: RA(J2000) = 13h 55m 1.44s Dec(J2000) = +47d 24' 40.5" with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 58 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 1.72e+20 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 1.85e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 139 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 0.01. Burst Advocate for this burst is P.A. Curran (pac AT mssl.ucl.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: 10131 SUBJECT: GRB 091104: Enhanced Swift-XRT position DATE: 09/11/04 15:56:13 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 677 s of XRT Photon Counting mode data and 1 UVOT images for GRB 091104, 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 = 208.75624, +47.41054 which is equivalent to: RA (J2000): 13h 55m 1.50s Dec (J2000): +47d 24' 37.9" with an uncertainty of 1.6 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: 10134 SUBJECT: GRB 091104: Swift/UVOT Upper Limits DATE: 09/11/04 17:13:20 GMT FROM: Peter Curran at MSSL P.A. Curran (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 091104 139s after the BAT trigger (Curran et al., GCN 10130). No optical afterglow consistent with the enhanched XRT position (Osborne et al., GCN 10131) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the finding charts (FC) and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag ------------------------------------------------------- white 139 289 147 >20.56 (FC) u 297 547 246 >19.69 (FC) white 139 993 301 >20.84 v 628 6155 87 >18.53 b 553 746 39 >18.88 u 297 721 265 >19.74 w1 677 870 39 >18.45 m2 652 845 39 >18.26 w2 776 4636 151 >19.71 The values quoted above 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: 10135 SUBJECT: GRB 091104: Swift XRT Refined Analysis DATE: 09/11/04 20:04:49 GMT FROM: Antonia Rowlinson at U.of Leicester A. Rowlinson (U Leicester) and P.A. Curran (MSSL-UCL) report on behalf of the Swift-XRT team: We have analysed 2.7 ks of XRT data for GRB 091104 (Curran et al. GCN Circ. 10130), from 137 s to 16.5 ks after the BAT trigger. The data comprise 162 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 10131). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=0.55 (+0.24, -0.27). At T+226.54 s the decay steepens to an alpha of 4.86 (+0.35, -0.29) before breaking again at T+524.02 s to a final decay with index alpha=1.48 (+1.19, -0.29). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.298 (+0.103, -0.096). The best-fitting absorption column is 1.09 (+0.20, -0.19) x 10^21 cm^-2, in excess of the Galactic value of 1.7 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.31 (+0.22, -0.15) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (3.4 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 1.48, the count rate at T+24 hours will be 1.9 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x 10^-11 (6.5 x 10^-11) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00374875. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10136 SUBJECT: GRB 091104: Swift-BAT refined analysis DATE: 09/11/04 20:26:56 GMT FROM: Scott Barthelmy at NASA/GSFC J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), P.A. Curran (MSSL-UCL), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+903 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091104 (trigger #374875) (Curran, et al., GCN Circ. 10130). The BAT ground-calculated position is RA, Dec = 208.723, 47.391 deg, which is RA(J2000) = 13h 54m 53.6s Dec(J2000) = +47d 23' 25.8" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 82%. The mask-weighted light curve shows a sharp rise at ~T+2, a rather flat top, and ending at ~T+120 sec. T90 (15-350 keV) is 99.3 +- 20 sec (estimated error including systematics). The time-averaged spectrum from T-1.5 to T+120.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.74 +- 0.24. The fluence in the 15-150 keV band is 7.7 +- 1.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+83.34 sec in the 15-150 keV band is 0.4 +- 0.1 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/374875/BA/