//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9725 SUBJECT: GRB 090728: Swift detection of a burst DATE: 09/07/28 15:00:04 GMT FROM: Scott Barthelmy at NASA/GSFC V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P.A. Curran (MSSL-UCL), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), N. P. M. Kuin (MSSL), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), P. Romano (INAF-IASFPA), T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-IASFPA), M. H. Siegel (PSU), M. Stamatikos (NASA/ORAU) and M. A. Stark (PSU) report on behalf of the Swift Team: At 14:45:45 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090728 (trigger=358574). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 29.660, +41.647 which is RA(J2000) = 01h 58m 38s Dec(J2000) = +41d 38' 49" 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 20 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 14:47:36.5 UT, 110.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 29.65234, 41.63270 which is equivalent to: RA(J2000) = 01h 58m 36.56s Dec(J2000) = +41d 37' 57.7" with an uncertainty of 4.2 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 consistent with the Galactic value of 7.35e+20 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 3.90e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 116 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 3-sigma upper limit is 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 0.07. The XRT position is near a bright (< 6.5 mag) star. Burst Advocate for this burst is V. Mangano (vanessa AT ifc.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: 9726 SUBJECT: GRB 090728A: Faulkes Telescope North Optical Afterglow Candidate DATE: 09/07/28 15:41:48 GMT FROM: Andrea Melandri at Liverpool John Moores U A. Melandri, C.G. Mundell, Z. Cano, R.J. Smith, I.A. Steele, S. Kobayashi, C.J. Mottram, D.F. Bersier (Liverpool JMU),A. Gomboc (Ljubljana), C. Guidorzi (INAF-OAB) report: "The 2-m Faulkes Telescope North robotically followed up GRB090728 (SWIFT trigger 358574; Mangano et al. GCN 9725) beginning about 9.6 min after the GRB trigger time. We identify a rapidly fading optical counterpart at: RA (J2000)=01:58:36.6 Dec(J2000)=+41:37:59.6 This source is not detected in our R-band images, but is detected in SDSS-I band images with i'=19.55+/-0.3 mag (at a mean time of 13.2 min after the burst) wrt USNO-B1 I-mag. Spectroscopic followup is encouraged." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9727 SUBJECT: GRB 090728, RIMOTS optical upper limits DATE: 09/07/28 17:32:46 GMT FROM: Hidenori Hayasi at Miyazaki U Sub:GRB 090728, RIMOTS optical upper limits K.Noda, H.Hayasi, E.Sonoda, N.Ohmori, K.Kono A.Daikyuji, Y.Nisioka, M.Yamauchi (University of Miyazaki) We have observed the field covering the error circle of GRB 090728 (Swift trigger 358574, GCN 9725, V. Mangano et al.) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 14:46:53 UT, about 23 sec after the Swift trigger time. We have compared our data of 30 sec exposures with the USNO-A2.0 catalog, There is no new source at the reported position. (Swift trigger 358574, GCN 9725, V. Mangano et al.) the upper limits are as follows: -------------------------------------------------------------- Start(UT) End(UT) Num. of frames Limit (mag.) -------------------------------------------------------------- 14:59:59 15:00:29 1 13.8 14:46:53 15:00:29 11 15.4 --------------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9729 SUBJECT: GRB 090728: Enhanced Swift-XRT position DATE: 09/07/28 19:59:43 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 2365 s of XRT Photon Counting mode data and 4 UVOT images for GRB 090728, 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 = 29.65290, +41.63313 which is equivalent to: RA (J2000): 01h 58m 36.70s Dec (J2000): +41d 37' 59.3" 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, arXiv:0812.3662). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9730 SUBJECT: GRB 090728: Swift/UVOT Upper Limits DATE: 09/07/28 22:58:42 GMT FROM: Patricia Schady at MSSL/Swift GRB 090728: Swift/UVOT Upper Limits P.A. Curran (MSSL-UCL), V. Mangano (INAF-IASFPA), report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 090728 117s after the BAT trigger (Mangano et al., GCN 9725). No optical afterglow consistent with the refined XRT position (Osborne et al., GCN 9729) or the optical counterpart (Melandri et al. , GCN 9726) is detected in the UVOT exposures. This is consistent with the R-band non-detection of Melandri et al. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the initial finding chart (FC) and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag v 422 6883 479 > 20.70 b 372 6643 491 > 21.45 u 117 366 150 > 20.00 (FC) u 117 6437 842 > 21.34 uw1 472 6233 452 > 21.05 um2 447 6026 452 > 20.75 uw2 398 6849 490 > 20.89 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9734 SUBJECT: GRB 090728: Swift XRT refined analysis DATE: 09/07/29 15:26:40 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano, B. Sbarufatti (INAF IASF Pa) report on beahalf the Swift XRT Team: We have analysed 9.8 ks of XRT data for GRB 090728 (Mangano et al. GCN Circ. 9725), from 116.9 s to 53.1 ks after the BAT trigger. The data comprise 55.3 s in Windowed Timing (WT) mode from T+116.9 s to T+172.2 s, with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 9729). The 0.3-10 keV XRT light curve is well modeled by a doubly broken power law with initial decay slope -5.5 ± 0.5, first break at T+204 ± 10 s, plateau phase slope -0.11 ± 0.14, second break at T+1.8 ± 1.2 ks and final slope -1.7 ± 0.1. Decaying at the present rate the source will reach a level of 2e-4 counts/s on July 30 at 14:45 UT (48 h after the trigger). We extracted the average WT spectrum of the early decay phase (55.3 s exposure), and the average PC spectra of the plateau phase (866 s exposure, from T+174 s to T+1071 s) and the final decay phase (7.4 ks exposure, from T+4383 s to T+18.4 ks). The three spectra are well fitted by an absorbed power law model with NH consistent with the Galactic value of 7.35e20 cm-2 (Kalberla et al. 2005) and photon indices of 2.4 ± 0.4, 1.8 ± 0.2, and 2.0 ± 0.3, respectively. The average 0.3-10 keV observed [unabsorbed] fluxes are 1.6e-10 [2.9e-10] erg cm-2 s-1, 2.7e-11 [3.0e-11] erg cm-2 s-1, and 1.5e-12 [2.3e-12] erg cm-2 s-1, respectively. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00358574. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9736 SUBJECT: GRB 090728: Swift-BAT refined analysis DATE: 09/07/29 20:08:49 GMT FROM: Scott Barthelmy at NASA/GSFC D. M. Palmer (LANL), 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), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), 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-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 090728 (trigger #358574) (Mangano, et al., GCN Circ. 9725). The BAT ground-calculated position is RA, Dec = 29.644, 41.632 deg which is RA(J2000) = 01h 58m 34.5s Dec(J2000) = +41d 37' 53.7" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 37%. The mask-weighted light curve shows a single pulse starting at ~T-10 sec, peaking at ~T+2 sec, and ending at ~T+70 sec. T90 (15-350 keV) is 59 +- 18 sec (estimated error including systematics). The time-averaged spectrum from T-5.0 to T+63.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.05 +- 0.26. The fluence in the 15-150 keV band is 1.0 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.25 sec in the 15-150 keV band is 1.0 +- 0.3 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/358574/BA/