//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7753 SUBJECT: GRB 080520: Swift detection of a burst with optical afterglow DATE: 08/05/20 22:49:07 GMT FROM: David Palmer at LANL D. Grupe (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), V. Mangano (INAF-IASFPA), K. M. McLean (GSFC/UMD), J. P. Osborne (U Leicester), D. M. Palmer (LANL), D. Perez (U Leicester), T. Sakamoto (NASA/UMBC), M. Stamatikos (NASA/ORAU), M. C. Stroh (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 22:20:24 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080520 (trigger=312047). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 280.192, -55.004 which is RA(J2000) = 18h 40m 46s Dec(J2000) = -55d 00' 13" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two peaks with a duration of about 15 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 22:22:04.3 UT, 99.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright uncatalogued X-ray source. The position, astrometrically enhanced by aligning promptly available UVOT field source positions to the USNO-B1 catalogue, is RA,Dec = 280.19337, -54.99181 (degrees) which is equivalent to: RA (J2000.0) = 18 40 46.41 DEC (J2000.0) = -54 59 30.5 with an uncertainty of 2.8 arcsec (radius, 90% containment). This position is 44.0 arcsec from the BAT position, inside the BAT error circle. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 106 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA (J2000.0) = 18:40:46.41 Dec (J2000.0) = -54:59:31.1 with an estimated uncertainty of 0.6 arcsec (90%, radius). The estimated magnitude is white = 19.8 +/- 0.1 mag. No correction has been made for Galactic extinction. Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 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: 7754 SUBJECT: GRB 080520: Swift XRT Refined Analysis DATE: 08/05/21 04:32:15 GMT FROM: Dirk Grupe at PSU/Swift-XRT Dirk Grupe reports on behalf of the Swift-XRT team: The XRT began observing the field of GRB 080520 (trigger=312047; Grupe et al., GCN Circ 7753) on 2008-May-20 at 22:22:04.3 UT, 99.5 seconds after the BAT trigger. The 0.3-10 keV X-ray light curve of the first two orbits displays a single decay with a slope alpha=1.04+/-0.07. The spectrum of the Photon Counting data of the first two orbits can be well fitted by an absorbed single powerlaw model with a photon index Gamma = 2.12 +/- 0.20 and a column density consistent with the Galactic value of 6.48e20 cm-2 If the underlying powerlaw decay continues as is, we predict an XRT count rate of 1e-3 counts/s at T+24 hours or 5e-14 ergs/s/cm2 and at T+48 hours 4e-4 counts/s or 2e-14 ergs/s/cm2. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7755 SUBJECT: GRB 080520: Enhanced Swift-XRT position DATE: 08/05/21 04:32:43 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 497 s of overlapping XRT Photon Counting mode and UVOT data for GRB 080520, 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 = 280.19385, -54.99160 which is equivalent to: RA (J2000): 18h 40m 46.52s Dec (J2000): -54d 59' 29.8" with an uncertainty of 1.9 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: 7756 SUBJECT: GRB 080520, GROND observations DATE: 08/05/21 06:24:35 GMT FROM: Andrea Rossi at TLS Tautenburg This is a multi-part message in MIME format. --bound1211350827 Content-Type: text/plain Content-Transfer-Encoding: 7bit A.Rossi, R. Filgas (Tautenburg), T. Kruehler, J. Greiner (MPE Garching), S. Klose (Tautenburg), A. Kupcu-Yoldas, A. Yoldas, and G. Szokoly (Eoetvoes Univ. Budapest and MPE) report on behalf of the GROND team: We observed the field of GRB 080520 observed by SWIFT (D. Grupe et al. GCN 7753) simultaneously in grizJHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPI/ESO telescope at La Silla (Chile). Observations started at 01:19 UT, about 2.9 hrs after the GRB. At this time, the GRB location was becoming visible at 20 degrees above horizon. Observations were performed at relatively high airmass and under challenging sky conditions with cirrus and a bright moon. The afterglow candidate detected by UVOT, reported by D.Grupe et al. (GCN 7753) is detected in g'r'i'z' J , implying a redshift smaller than 3.5. We estimate a rough magnitude of i'=21.38 +/-0.4 at 3.25 hrs after the GRB, calibrated against USNO-B field stars. We stop observations due to bad sky conditions. --bound1211350827-- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7757 SUBJECT: GRB 080520: VLT redshift DATE: 08/05/21 11:38:56 GMT FROM: Pall Jakobsson at U Hertfordshire Pall Jakobsson (U. Hertfordshire), Johan P. U. Fynbo, Daniele Malesani, Jens Hjorth and Bo Milvang-Jensen (DARK, NBI) report on behalf of a larger collaboration: Using FORS2 on the Very Large Telescope, we have obtained 3*30 min spectra (grism 300V) of the optical afterglow of GRB 080520 (Grupe et al., GCN 7753). The acquisition image shows it to have R = 23.0 +/- 0.5 on May 21.235 (7.3 hours post burst). A firm upper limit of z < 2.4 can be placed on the redshift of GRB 080520 from the lack of Ly-alpha forest lines in the spectrum of the afterglow. This is consistent with the GROND observations (Rossi et al., GCN 7756). The combined spectrum shows an emission line, presumably corresponding to [O II] 3727 at z = 1.545. At this redshift we also find the Mg II doublet (2796,2803) and Mg I (2852). We thank the Paranal staff for excellent support, especially Yuri Beletsky and Patricia Guajardo. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7758 SUBJECT: GRB080520: Swift/UVOT observations DATE: 08/05/21 13:12:58 GMT FROM: Samantha Oates at MSSL S.R. Oates (MSSL/UCL) and D. Grupe (PSU) report on behalf of the Swift/UVOT team The Swift/UVOT began settled observations of the field of GRB 080520, 105s after the BAT trigger (Grupe et al., GCN 7753). We detect the afterglow in the white, v filters at the position: RA(J2000.0) = 18:40:46.30 DEC(J2000.0) = -54:59:31.0 with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). This position is consistent with the UVOT enhanced XRT position (Goad et al., GCN 7755). UVOT magnitudes and 3 sigma upper limits are reported below for the single and coadded images: Filter Tstart(s) Tstop Expo(s) Magnitude/3sigUL ----------------------------------------------------- white 105 204 98 19.59 +/- 0.12 white 858 958 98 20.58 +/- 0.28 v 211 610 400 20.26 +/- 0.38 v 964 1299 330 19.96 +/- 0.45 b 691 6273 216 > 20.92 u 666 6068 197 > 20.60 w1 641 5862 236 > 20.33 m2 617 7079 418 > 20.38 w2 720 6684 216 > 20.25 ----------------------------------------------------- These magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E{B-V} = 0.08 mag (Schlegel et al. 1998). The photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7761 SUBJECT: GRB 080520, Swift-BAT refined analysis DATE: 08/05/21 17:04:22 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080520 (trigger #312047) (Grupe, et al., GCN Circ. 7753). The BAT ground-calculated position is RA, Dec = 280.179, -54.964 deg which is RA(J2000) = 18h 40m 42.9s Dec(J2000) = -54d 57' 51.2" with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a single peak starting at T_zero and ending at ~T+3 sec. T90 (15-350 keV) is 2.8 +- 0.7 sec (estimated error including systematics). The time-averaged spectrum from T-0.3 to T+2.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.90 +- 0.51. The fluence in the 15-150 keV band is 5.5 +- 1.4 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.31 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/312047/BA/ We note that the fluence ratio in a simple power-law fit between the 25-50 keV band and the 50-100 keV band is 1.88. This fluence ratio is larger than 1.32 which can be achieved in the Band function of alpha=-1.0, beta=-2.5, and Epeak=30 keV. Thus, preliminary analysis shows that Epeak of the burst is very likely around or below 30 keV. Therefore the burst can be classified as an X-ray flash (e.g. Sakamoto et al. ApJ, 679, 570). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7771 SUBJECT: GRB 080520: VLT host detection DATE: 08/05/24 15:19:17 GMT FROM: Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center D. Malesani (DARK), P. Jakobsson (Univ. Hertfordshire), J. P. U. Fynbo, J. Hjorth, B. Milvang-Jensen (DARK), report on behalf of a larger collaboration: We further inspected our images and spectra (Jakobsson et al., GCN 7757) of the afterglow of GRB 080520 (Grupe et al., GCN 7753). A faint extension is visible in our images (seeing 0.7") underlying the afterglow emission, which may be due to a relatively bright host galaxy. This is consistent with the 2D trace of the spectrum, which reveals the proposed [O II] line to be also spatially extended. Using the relations by Kennicutt (1998, ARA&A, 36, 189), the flux of the [O II] line (not corrected for extinction) corresponds to a star formation rate (SFR) of approximately 15 M_Sun/yr. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8490 SUBJECT: Radio observation of GRB 080520 with ATCA DATE: 08/11/07 01:40:35 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 080520 (GCN 7761) at 4.8 GHz with the Australia Telescope Compact Array (ATCA) on June 01, 2008 between 08:41:15 UT and 09:45:25 UT. We did not detect a radio source at the BAT position of the GRB 080520 (GCN 7761). The radio flux density at the GRB position is 0.297 +/- 0.217 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_080520_field_image