//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15088 SUBJECT: GRB 130812A: Swift detection of a burst DATE: 13/08/12 22:38:46 GMT FROM: Scott Barthelmy at NASA/GSFC V. D'Elia (ASDC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), V. Mangano (PSU), C. B. Markwardt (NASA/GSFC) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 22:22:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130812A (trigger=566228). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 92.402, -13.295 which is RA(J2000) = 06h 09m 37s Dec(J2000) = -13d 17' 42" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks with a total duration of about 10 sec. The peak count rate was ~4500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 22:24:09.6 UT, 77.0 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 92.3955, -13.2875 which is equivalent to: RA(J2000) = 06h 09m 34.92s Dec(J2000) = -13d 17' 15.1" with an uncertainty of 2.1 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 (1.51 x 10^21 cm^-2, Kalberla et al. 2005), with an excess column of 1.5 (+1.52/-1.37) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 138 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 19.2 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 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.23. Burst Advocate for this burst is V. D'Elia (delia 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: 15089 SUBJECT: GRB 130812A: Enhanced Swift-XRT position DATE: 13/08/13 08:46:24 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 2469 s of XRT Photon Counting mode data and 5 UVOT images for GRB 130812A, 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 = 92.39590, -13.28816 which is equivalent to: RA (J2000): 06h 09m 35.02s Dec (J2000): -13d 17' 17.4" 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: 15090 SUBJECT: GRB 130812A: Swift-XRT refined Analysis DATE: 13/08/13 10:39:04 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), P. D'Avanzo (INAF-OAB), A. Maselli (INAF-IASFPA), V. Mangano (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester) and V. D'Elia report on behalf of the Swift-XRT team: We have analysed 8.9 ks of XRT data for GRB 130812A (D'Elia et al. GCN Circ. 15088), from 62 s to 22.3 ks after the BAT trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 15089). The light curve can be modelled with a power-law decay with a decay index of alpha=0.86 (+/-0.03). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.04 (+0.17, -0.16). The best-fitting absorption column is 3.0 (+/-0.6) x 10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (6.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.0 (+/-0.6) x 10^21 cm^-2 Galactic foreground: 1.5 x 10^21 cm^-2 Excess significance: 4.3 sigma Photon index: 2.04 (+0.17, -0.16) If the light curve continues to decay with a power-law decay index of 0.86, the count rate at T+24 hours will be 7.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.9 x 10^-13 (4.6 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/00566228. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15091 SUBJECT: GRB 130812A: GROND upper limits DATE: 13/08/13 13:19:03 GMT FROM: Jochen Greiner at MPI K. Varela (MPE Garching), D.A. Kann (TLS Tautenburg), J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 130812A (Swift trigger 566228; D'Elia et al. 2013, GCN #15088) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Observations started at 10:13 UT on 13 Aug. 2013, 11.8 hrs after the GRB trigger. They were performed at an average seeing of 2.5" and at an average airmass of 1.4. In 212 sec exposure in g'r'i'z' and 360 sec exposure in JHK we do not detect a source within the 1.8 arcsec Swift-XRT error circle reported by Evans et al. (2013; GCN #15089) down to (all in the AB system) g' > 22.4, r' > 22.6, i' > 21.9, z' > 21.7, J > 20.3, H > 19.4 and K > 18.8 The given limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.23 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15092 SUBJECT: GRB 130812A, Swift-BAT refined analysis DATE: 13/08/13 16:12:20 GMT FROM: Takanori Sakamoto at AGU D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-144 to T+431 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130812A (trigger #566228) (D'Elia, et al., GCN Circ. 15088). The BAT ground-calculated position is RA, Dec = 92.387, -13.285 deg which is RA(J2000) = 06h 09m 32.8s Dec(J2000) = -13d 17' 06.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%. The mask-weighted light curve shows multiple spikes peaking at T0, T0+4 sec and T0+7 sec. T90 (15-350 keV) is 7.6 +- 0.5 sec (estimated error including systematics). The time-averaged spectrum from T-0.3 to T+8.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.52 +- 0.11. The fluence in the 15-150 keV band is 5.9 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.14 sec in the 15-150 keV band is 2.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis will be available at http://gcn.gsfc.nasa.gov/notices_s/566228/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15093 SUBJECT: GRB 130812A: Swift/UVOT Upper Limits DATE: 13/08/13 16:15:52 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130812A 139 s after the BAT trigger (D'Elia et al., GCN Circ. 15088). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 15089) 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 u_FC 139 389 246 >20.3 v 445 12868 1191 >20.5 b 394 11236 1459 >21.7 u 139 7030 884 >20.8 w1 494 6825 491 >20.5 m2 469 6619 452 >20.3 w2 421 12142 1376 >21.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.23 in the direction of the burst (Schlegel et al. 1998).