//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5394 SUBJECT: GRB 060804: Swift detection of a burst with a possible UVOT counterpart DATE: 06/08/04 08:10:13 GMT FROM: Scott Barthelmy at NASA/GSFC H. Z. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMD), N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU), C. B. Markwardt (GSFC/UMD), M. J. Page (UCL-MSSL), K. L. Page (U Leicester), D. M. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU) and G. Tagliaferri (INAF-OAB) report on behalf of the Swift Team: At 07:28:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060804 (trigger=222546). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 112.201, -27.231 {07h 28m 48s, -27d 13' 52"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 10 sec. The peak count rate was ~600 counts/sec (15-350 keV), at ~5 sec after the trigger. The XRT began taking data at 07:30:21 UT, 121 seconds after the BAT trigger. Although the XRT on-board centroid algorithm did not find a source in the image, ground analysis revealed an uncatalogued point source at a position of RA(J2000) = 07h 28m 49.40s, Dec(J2000) = -27d 12' 58.9", with an estimated error of 3.9 arcsec radius (90% containment). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 128 seconds after the BAT trigger. A possible afterglow candidate is seen in the 2.7'x2.7' sub-image with an estimated magnitude of V=17 at position RA(J2000) = 07h 28m 49.36s Dec(J2000) = -27d 12' 56.7" with an estimated error of 1". The Be star SPH 10 is in the BAT error circle. However, it is inconsistent with the XRT and UVOT source location (2 arcminutes) and is therefore unlikely to be associated with the burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5395 SUBJECT: GRB 060804: Refined analysis of the Swift-BAT burst DATE: 06/08/04 18:00:12 GMT FROM: Scott Barthelmy at NASA/GSFC J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (GSFC/UMD), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), H. Z. Ziaeepour (UCL-MSSL) on behalf of the Swift-BAT team: Using the data set from T-240 to T+800 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060804 (trigger #222546) (Ziaeepour, et al., GCN Circ. 5394). The BAT ground-calculated position is RA,Dec = 112.216, -27.228 deg {7h 28m 51.8s, -27d 13' 41.8"} (J2000) +- 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 18%. The mask-weighted lightcurve shows two overlapping peaks. The first starts at T-14 sec and peaking at T-10 sec. The second peaks at T+4 sec. T90 (15-350 keV) is 16 +- 2 sec (estimated error including systematics). The time-averaged spectrum from T-12.3 to T+5.5 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.78 +- 0.28. The fluence in the 15-150 keV band is 5.1 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+4.46 sec in the 15-150 keV band is 1.2 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5396 SUBJECT: GRB 060804: Swift-XRT Team Refined Analysis DATE: 06/08/04 19:29:01 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) & H.Z. Ziaeepour (UCL-MSSL) report on behalf of the Swift-XRT team: We have analysed the first 6 orbits of the XRT data obtained for GRB 060804 (trigger 222546). Using these 4340 seconds of data, we find a refined position of: RA(J2000) = 07 28 49.40 Dec(J2000) = -27 12 58.7 with an uncertainty of 3.6 arcsec (90% containment). This is 0.2 arcsec from the initial XRT position stated in GCN 5394 (Ziaeepour et al.) and 53.8 arcsec from the refined BAT position in GCN 5395 (Tueller et al.) The X-ray afterglow was sufficiently faint for the XRT to collect data only in Photon Counting mode. During the first orbit, the count rate remained close to constant, at ~1.5 count s^-1. Orbits 2-6, however, show a power-law decay, with a slope alpha = 0.86 +/- 0.22. There is no evidence for spectral evolution between the first orbit (where the light-curve is flat) and the later decay, with the spectrum being well fitted with a simple power-law of Gamma = 2.24 +/- 0.22, with the Galactic absorbing column of 5.34e21 cm^-2; no excess NH is required. Between 130 and 700 seconds after the burst, the 0.3-10 keV observed (unabsorbed) flux was 6.95e-11 (1.44e-10) erg cm^-2 s^-1. If the afterglow continues to decay at the same rate, the count rate at 24 hours is predicted to be 0.012 count s^-1, corresponding to an observed (unabsorbed) flux of 6.02e-13 (1.25e-12). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5397 SUBJECT: GRB 060804: Swift UVOT observations DATE: 06/08/04 21:44:33 GMT FROM: Mat Page at MSSL/Swift S. B. Pandey, M. De Pasquale, M. J. Page and H.Z. Ziaeepour (UCL-MSSL) report on behalf of the Swift/UVOT team: The Swift UVOT began taking settled exposures on the field of the long duration GRB 060804 (BAT Trigger #222546), 128s after the BAT trigger (Ziaeepour et al., GCN Circ. 5394). The optical afterglow candidate (RA(J2000) = 07h 28m 49.36s Dec(J2000) = -27d 12' 56.7") reported by Ziaeepour et al. 2006 (GCN Circ. 5394) is clearly detected in early frames. The fading behaviour of the candidate before the later frames confirms that it is the afterglow of GRB 060804. Detections in the initial V and White images, and 3-sigma upper limits in the later, coadded images are listed below. Filter T_range(s) Exposure (s) Magnitude White 126-225 98 17.9+-0.1 V 231-631 393 17.7+-0.1 Filter T_range(s) Exposure (s) 3-sigma UL White 5211-12280 253 > 20.1 V 5621-5820 197 > 19.4 B 709-12219 944 > 20.5 U 685-18065 896 > 19.9 UVW1 661-15696 408 > 19.8 UVM2 637-6025 216 > 19.5 UVW2 5417-21845 747 > 19.7 T_range is calculated from the time of the trigger. We caution that photometry of this afterglow is complicated by the presence of a nearby source. These measurements have not been corrected for the estimated Galactic reddening of E_(B-V) = 0.657 mag (Schlegel et al. 1998). We caution that the extinction estimate for this burst, which has |Galactic latitude| < 5 deg, is unreliable.