//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7767 SUBJECT: GRB 080523: Swift detection of a burst DATE: 08/05/23 21:34:28 GMT FROM: David Palmer at LANL M. C. Stroh (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), C. Gronwall (PSU), D. Grupe (PSU), S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), D. Perez (U Leicester), J. L. Racusin (PSU), M. Stamatikos (NASA/ORAU), T. N. Ukwatta (GSFC/GWU) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 21:21:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080523 (trigger=312242). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 20.732, -64.053 which is RA(J2000) = 01h 22m 56s Dec(J2000) = -64d 03' 12" 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 15 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~5 sec after the trigger. The XRT began observing the field at 21:23:17.7 UT, 86.4 seconds after the BAT trigger. XRT found a bright, uncatalogued, fading X-ray source located at RA, Dec 20.7992, -64.0322 which is equivalent to: RA(J2000) = 01h 23m 11.8s Dec(J2000) = -64d 01' 55.9" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 129 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to assess possible redshift constraints using X-ray spectroscopy and the nH-z relation from Grupe et al. (2007). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 110 seconds after the BAT trigger. No 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 18.5 mag. data for the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is M. C. Stroh (stroh AT astroh.org). 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: 7768 SUBJECT: GRB 080523: Enhanced Swift-XRT position DATE: 08/05/24 04:34:35 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 463 s of overlapping XRT Photon Counting mode and UVOT data for GRB 080523, 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 = 20.79796, -64.03081 which is equivalent to: RA (J2000): 01h 23m 11.51s Dec (J2000): -64d 01' 50.9" with an uncertainty of 1.5 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7769 SUBJECT: Swift/UVOT observations of GRB 080523 DATE: 08/05/24 12:02:56 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (MSSL/UCL), and M. C. Stroh (PSU), report on behalf of the Swift UVOT team The Swift UltraViolet/Optical Telescope (UVOT) began observations of GRB 080523, on May 23, 2008, at UT, 112 seconds after the initial Swift BAT trigger (Stroh et al., GCN Circ. 7767). We detect no source at the enhanced Swift XRT position (Osborne, GCN Circ.7768). The 3-sigma limiting magnitudes for GRB080523 are given below for the two initial observations, and for summed observations in each of the UVOT filters: Filter Tstart(s) Tstop(s) Exp(s) Magnitude white 112 211 99.8 > 20.78 v 218 617 399.8 > 19.93 white 112 12001 1211.2 > 21.80 v 218 6037 819.2 > 19.86 uvm2 624 6242 439.2 > 20.15 uvw1 649 6448 439.2 > 20.20 u 673 6649 435.9 > 19.92 b 698 11088 1118.9 > 21.56 uvw2 728 12430 841.6 > 20.77 The values quoted above are on the UVOT Photometric System (Poole et al, 2008, MNRAS 383,627). They are not corrected for the expected galactic reddening of E(B-V) = 0.025 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7770 SUBJECT: GRB 080523: VLT optical observations DATE: 08/05/24 14:32:01 GMT FROM: Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center Johan P. U. Fynbo, Daniele Malesani (DARK), Pall Jakobsson (Univ. Hertfordshire), Bo Milvang-Jensen and Jens Hjorth (DARK), report on behalf of a larger collaboration: We observed the field of GRB 080523 (Stroh et al., GCN 7767) with the ESO VLT equipped with FORS2. Photometric observations were conducted on 2008 May 24, between 8:14 and 8:27 UT (about 10.9 hr after the GRB). Inside the revised XRT error circle (Osborne et al., GCN 7768), we detect a faint source at coordinates (J2000): RA = 01:23:11.61 Dec = -64:01:51.8 Lacking any information on variability, we cannot assess whether this source is associated with GRB 080523. A spectrum of the object shows detection of continuum in the blue down to 4200 AA, implying a redshift limit z < 2.5. Further analysis is underway. We note the presence of two further, faint sources close to, but slightly outside of, the refined XRT error circle at (RA, Dec) = (01:23:11.21, -64:01:53.9) and (01:23:10.88, -64:01:50.4). We acknowledge excellent support and positive initative from the ESO observing staff, particularly Yuri Beletsky and Patricia Guajardo. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7772 SUBJECT: GRB 080523, Swift-BAT refined analysis DATE: 08/05/24 21:16:50 GMT FROM: Scott Barthelmy at NASA/GSFC D. Palmer (LANL), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), M. C. Stroh (PSU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 080523 (trigger #312242) (Stroh, et al., GCN Circ. 7767). The BAT ground-calculated position is RA, Dec = 20.769, -64.060 deg, which is RA(J2000) = 01h 23m 04.4s Dec(J2000) = -64d 03' 36.0" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a FRED-like peak starting at ~T-10 sec, peaking at ~T+4, and ending at ~T+80 sec. There is a weak second peak starting,ending at 80,110 sec, respectively. T90 (15-350 keV) is 102 +- 15 sec (estimated error including systematics). The time-averaged spectrum from T-6.1 to T+111.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.65 +- 0.18. The fluence in the 15-150 keV band is 8.8 +- 1.0 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+3.89 sec in the 15-150 keV band is 0.5 +- 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/312242/BA/ This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria (Ukwatta et al. arXiv:0802.3815). 1) Power Law photon index = 1.65 (PL photon index < 2) 2) 1-s peak photon flux = 0.51 (1-s peak photon flux < 1.0 ph/cm2/s) 3) Light curve variance = 1.2e-05 (Variance < 0.0001) 4) T90/(Peak photon flux) = 201 (T90/(Peak photon flux) > 100) Based on a limited sample of bursts, these criteria yield an 85% chance it has a redshift greater than 3.5. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7773 SUBJECT: GRB 080523: Swift-XRT refined analysis DATE: 08/05/24 22:00:24 GMT FROM: Michael Stroh at PSU/Swift M. C. Stroh and D. Grupe (PSU) report on behalf of the Swift-XRT Team: We have analyzed the first eight orbits of Swift-XRT data obtained for GRB 080523 (Stroh et al. GCN Circ. 7767), totaling 250 s of Windowed Timing (WT) data and 11.8ks of Photon Counting (PC) data. The light curve can be described as a single broken power-law with an initial decay index of 2.17 +/- 0.04 followed by a shallower decay index of 0.56 +/- 0.27 with a break at T+3.5ks. We predict a count rate at T+48 hours of 3.2e-3 cts/s. The WT data (93 - 343 seconds) can be modeled as an absorbed power law with photon index of 2.17 +/- 0.04 and a total absorbing column density that is consistent with the Galactic value of 2.1e20 cm^-2. The 0.3-10 keV absorbed (unabsorbed) flux during this time is 4.58e-10 (4.99e-10) erg cm^-2 s^-1. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7779 SUBJECT: GRB 080523: afterglow confirmation and redshift constraints DATE: 08/05/29 18:22:30 GMT FROM: Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center D. Malesani, J. P. U. Fynbo (DARK/NBI), A. de Ugarte Postigo (ESO), P. Jakobsson (Univ. Hertfordshire), J. Hjorth, B. Milvang-Jensen (DARK/NBI), report on behalf of a larger collaboration: We observed again the field of GRB 080523 (Stroh et al., GCN 7767) with the ESO VLT equipped with the FORS2 camera. Observations were carried out on 2008 May 28, at mean time 9:35 UT (4.5 days after the GRB) in the R band. The optical source identified by Fynbo et al. (GCN 7770) has clearly faded since our previous observation by at least 1.5 mag. This confirms that the object is the afterglow of GRB 080523. The refined coordinates (J2000, against USNO-B1.0) are RA = 01:23:11.56 Dec = -64:01:51.59 Residual, marginally significant emission is still detected close to the afterglow position. It is unclear whether this is related to the GRB. A finding chart showing the field in the two epochs is posted at http://www.astro.ku.dk/~malesani/GRB/080523/080523_finder.jpg Close inspection of our spectra (Fynbo et al., GCN 7770) fails to reveal any convincing absorption or emission feature. The object has a blue continuum, and flux is detected down to ~4070 AA. A conservative limit to the redshift is set by the absence of Lyman-alpha forest redward of ~4900 AA, which implies z < 3. This limit rules out a high redshift as suggested by the burst gamma-ray properties (Palmer et al., GCN 7772). We acknowledge significant support from the ESO staff at Paranal, particularly Linda Schmidtobreick. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8491 SUBJECT: Radio observation of GRB 080523 with ATCA DATE: 08/11/07 01:47:29 GMT FROM: Aquib Moin at CIRA/ATNF Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope National Facility), Steven Tingay (Curtin Institute of Radio Astronomy), Chris Phillips (Australia Telescope National Facility), Gregory Taylor (University of New Mexico), Mark Wieringa (Australia Telescope National Facility) and Ralph Martin (Perth Observatory) report: We observed the BAT refined position of the GRB 080523 (GCN 7772) at 4.8 GHz with the Australia Telescope Compact Array (ATCA) on June 01, 2008 between 04:12:15 UT and 06:37:35 UT. We did not detect a radio source at the BAT position of the GRB 080523 (GCN 7772). The radio flux density at the GRB position is -0.069 +/- 0.172 mJy at 4.8 GHz (1-sigma). The Australia Telescope Compact Array (/ Parkes telescope / Mopra telescope / Long Baseline Array) is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. See field image at: http://cira.ivec.org/dokuwiki/doku.php/grb/grb_080523_field_image