//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15082 SUBJECT: GRB 130807A: Swift detection of a GRB or Galactic transient DATE: 13/08/07 10:50:03 GMT FROM: David Palmer at LANL A. Melandri (INAF-OAB), D. N. Burrows (PSU), P. A. Evans (U Leicester), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 10:25:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130807A (trigger=565651). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 269.801, -27.613 which is RA(J2000) = 17h 59m 12s Dec(J2000) = -27d 36' 44" 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 at least 30 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 10:27:08.2 UT, 85.0 seconds after the BAT trigger. Although a bright and variable source is apparent in the promptly downloaded light curve, the instrument did not centroid on the source in the initial 2.5-s promptly downloaded image, and the XRT stayed in WT mode for the remainder of the short first snapshot until Swift slewed away from the target. We therefore will have to wait until the second orbit to localize the XRT counterpart. UVOT took a finding chart exposure of 166 seconds with the U filter starting 145 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 25% of the BAT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain extinction expected. Due to the proximity of this source to the Galactic center (3.3 degrees from the center) it is more likely that this is a Galactic source rather than a cosmological GRB. Determination of the nature of this source will require the full downlinked data. Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.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: 15083 SUBJECT: GRB 130807A, Swift-BAT refined analysis DATE: 13/08/08 14:35:14 GMT FROM: Hans Krimm at NASA-GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), A. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130807A (trigger #565651) (Melandri, et al., GCN Circ. 15082). The BAT ground-calculated position is RA, Dec = 269.801, -27.616 deg, which is RA(J2000) = 17h 59m 12.4s Dec(J2000) = -27d 36' 56.7" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 92%. Based on the currently available event data, the mask-weighted light curve shows an initial FRED-like peak starting at T-10 sec, peaking at T=0 sec and decaying to background by T+50 sec. This is followed by at least two more weaker peaks, one from roughly T+90 sec to T+130 sec and the second beginning at T+160 sec and continuing until the data cuts off at T+243 seconds. The two later peaks are coincident with flares seen in the Swift/XRT data. We note also that the Swift satellite slewed away from the source location at ~T+300 seconds, while an XRT flare was still ongoing. Since we do not have all of the data, we cannot determine T90 at this time. The time-averaged spectrum from T-12.18 to T+163.82 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.31 +- 0.89, and Epeak of 75.9 +- 35.2 keV (chi squared 56.96 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-4.68 sec in the 15-150 keV band is 0.4 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.46 +- 0.17 (chi squared 63.40 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The current analysis of the BAT data does not allow us to distinguish between the interpretations of this event as either a GRB or galactic transient. These results will be updated as more event data becomes available. Examination of archival images from the Swift/BAT transient monitor through 3:03 UT, August 6, 2013 (~31.5 hours before the trigger) shows no sign of earlier emission from the location of trigger 565651. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/565651/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15085 SUBJECT: GRB 130807A: Swift-XRT refined analysis DATE: 13/08/08 19:48:08 GMT FROM: Andrea Melandri at INAF-OAB A. Melandri (INAF/OAB), D.N. Burrows (PSU), P. Romano (INAF-IASFPA), H.A. Krimm (GSFC/USRA), J.P. Osborne, P.A. Evans (U. Leicester), N. Gehrels (GSFC) report on behalf of the Swift team. We have analysed 14.4 ks of XRT data for GRB 130807A (Melandri et al. GCN Circ. 15082), from 88 s to 80 ks after the BAT trigger. The XRT position for this burst is RA, Dec = 269.8007, -27.6159 which is equivalent to: RA (J2000): 17h 59m 12.16s Dec (J2000): -27d 36' 57.5" with an uncertainty of 3.6 arcsec (radius, 90% confidence). In the first orbit (WT mode) the source is initially detected at a rate of ~10 XRT count/s, rising to ~100 c/s at the end of the first orbit. During this period the spectrum can be fit by an absorbed power- law model with a photon index of 1.56 +/- 0.08. The source showed an absorption column of (8.6 +/- 1.0) x 10^21 cm^-2, slightly in excess with respect to the Galactic value of 6 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 8.0 x 10^-11 (1.2 x 10^-10) erg cm^-2 count^-1. In the second orbit (PC mode) the source had become much fainter (~0.03 c/s), and much softer, with a photon index of 2.3 (+0.5, -0.4).The source still showed an absorption column (9.0 +/- 5.0 x 10^21 cm^-2) consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.0 x 10^-11 (1.7 x 10^-10) erg cm^-2 count^-1. Starting with the second orbit, the light curve rose from a count rate of ~0.015 c/s after ~4 ks to a maximum of ~0.06 c/s at ~10 ks (with slope of -1.5 +/- 0.1). After that it decayed with a slope of 0.9 +/- 0.1, reaching the count rate of ~0.012 c/s at ~75 ks. The light curve behaviour (at late times) is unusual, but not unprecedented, for a GRB. The BAT and XRT spectral indices are similar to those observed for GRB 060124 (BAT spectrum gamma = 1.89 +/- 0.19, XRT-WT spectrum gamma = 1.40+/-0.01, XRT-PC spectrum gamma = 2.1+/-0.1; Romano et al., 2006, A&A, 456, 917) and for the transient supermassive black hole Swift J1644+57 (Burrows et al., 2011, Nature, 476, 421), but inconsistent with what generally observed for a Supergiant Fast X-ray Transient. The dynamical range of GRB 130807A (~3300) is similar to what observed for GRB 060124 or for a typical SFXT, but very different from what was observed for Swift J1644+57. The source was not detected in the BAT transient monitor (15-50 keV) before 3:03 UT, August 6, 2013, the most recent monitor epoch currently available. Events like Swift J1644+57 or SFXTs are usually detected in X-rays for several days before the trigger, Swift J1644+57 behaved similarly. It is therefore likely that BAT trigger 565651 was a somewhat unusual GRB rather than a Galactic or extragalactic transient, in spite of its proximity to the Galactic center. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/possible_GRBs/00565651/source1 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15086 SUBJECT: GRB130807A: Swift/UVOT observations DATE: 13/08/08 19:53:04 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (UCL-MSSL) and A. Melandri (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130807A 145 s after the BAT trigger (Melandri et al., GCN Circ. 15082). No optical source consistent with the XRT position (Melandri et al., GCN Circ. 15085) is detected in the 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 summed exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 3572 3722 147 >20.3 white 3572 5573 541 >21.1 v 4348 5984 393 >19.3 b 3732 5369 393 >20.3 u_FC 145 311 163 >19.7 u 145 5164 360 >19.9 w1 4759 4959 197 >19.6 m2 4552 6078 284 >19.7 w2 4143 5780 393 >20.2 The magnitudes in the table are not corrected for the strong Galactic extinction corresponing to the reddening of E(B-V) = 2.03 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15087 SUBJECT: Correction to GCN Circ. 15086 "GRB130807A: Swift/UVOT observations" DATE: 13/08/08 20:08:00 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (UCL-MSSL) reports on behalf of the Swift/UVOT team: In the previous GCN Circ. 15086 "GRB130807A: Swift/UVOT observations", the sentence "No optical source" should be changed into "No uncatalogued optical source". I apologize for the mistake.