//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8059 SUBJECT: GRB 080805: Swift detection of a burst DATE: 08/08/05 08:13:07 GMT FROM: David Palmer at LANL C. Pagani (PSU), W. H. Baumgartner (GSFC/UMBC), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), D. Grupe (PSU), C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC), J. Mao (INAF-OAB), A. Moretti (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL), J. L. Racusin (PSU), P. Romano (INAF-IASFPA) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 07:41:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080805 (trigger=319036). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 314.231, -62.438 which is RA(J2000) = 20h 56m 55s Dec(J2000) = -62d 26' 16" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a FRED-like structure with a duration of about 50 sec. The peak count rate was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 07:42:38.3 UT, 63.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading uncatalogued X-ray source located at RA, Dec 314.22273, -62.44433 which is equivalent to: RA(J2000) = 20h 56m 53.46s Dec(J2000) = -62d 26' 39.6" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This position is 26.6 arcseconds from the BAT position, within the BAT error circle. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 3.45e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 74 seconds after the BAT trigger. No afterglow candidate is apparent in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle and 100% of the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.043. Burst Advocate for this burst is C. Pagani (pagani 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: 8060 SUBJECT: GRB 080805: GROND detection of possible afterglow DATE: 08/08/05 08:42:10 GMT FROM: Jochen Greiner at MPI T. Kruehler, F. Schrey, J. Greiner, C. Clemens, A. Yoldas (all MPE Garching), A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started observations of the field of GRB 080805 (Pagani et al. 2008, GCN #8059) in g'r'i'z'JHK at 07:45 UT, 3.5 min after the burst. We detect an optical/NIR afterglow candidate in the XRT error circle (Pagani et al. 2008, GCN #8059) in griz at: RA(J2000): 20h 56m 53.44 DEC(J2000): -62d 26' 39.8" with uncertainties of 0.5". We measure the following magnitudes, calibrated against USNO-B1 field stars: g = 21.7 +- 0.2 r = 20.5 +- 0.1 i = 20.1 +- 0.1 z = 19.9 +- 0.1 No statement about fading can be made at the moment. If this is the afterglow of GRB 080805, then its redshift is smaller than 3.5. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8061 SUBJECT: GRB 080805: Afterglow confirmation DATE: 08/08/05 11:17:52 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo (ESO), D. Malesani, P. M. Vreeswijk, J.P.U. Fynbo (DARK/NBI), P. Jakobsson (Univ. Hertfordshire), A.O. Jaunsen (Univ. Oslo), J. Sollerman (DARK/NBI and Univ. Stockholm), report: We observed the field of GRB 080805 (Pagani et al., GCN 8059) with the ESO VLT equipped with FORS2. We clearly identify the candidate afterglow first reported by Kruehler et al. (GCN 8060). From the first image, obtained at 07:50:49 UT (9.3 min after the burst) to 10:00:05 UT (138.5 min after the burst) the object faded by 2.0 magnitudes in the R band. We thus consider the afterglow candidate to be secure. We acknowledge excellent support from the observing staff at Paranal, especially to Patricia Guajardo and Yuri Belestky. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8062 SUBJECT: GRB 080805: VLT redshift DATE: 08/08/05 14:21:31 GMT FROM: Pall Jakobsson at U Hertfordshire P. Jakobsson (U. Hertfordshire), P. M. Vreeswijk (DARK/NBI), A. de Ugarte Postigo (ESO), D. Malesani, J. P. U. Fynbo (DARK/NBI) and J. Sollerman (DARK/NBI; U. Stockholm) report on behalf of a larger collaboration: Using FORS2 on the ESO Very Large Telescope, we have obtained low and medium resolution spectra (grisms 300V, 1200R and 1400V) of the optical afterglow of GRB 080805 (Kruehler et al., GCN 8060; de Ugarte Postigo et al., GCN 8061). The first spectrum was taken approximately an hour after the burst. A firm upper limit of z < 2.2 can be placed on the redshift of GRB 080805 from the lack of Ly-alpha forest lines in the spectrum of the afterglow. This is consistent with the GROND observations (Kruehler et al). The spectra display Fe II (2344,2382,2600) and the Mg II doublet (2796,2803) in absorption corresponding to a redshift of z = 1.20. There is also tentative evidence of an absorption system at z = 1.50 (Fe II and Mg II), but further analysis is required to confirm the reality of this system. We thank the Paranal staff for excellent support, especially Patricia Guajardo and Yuri Belestky. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8063 SUBJECT: GRB080805 optical limit by "Pi of the Sky" DATE: 08/08/05 14:26:10 GMT FROM: Marcin Sokolowski at Soltan Inst. Nuc Studies,Warsaw M.Cwiok, W.Dominik, G.Kasprowicz, A.Majcher, A.Majczyna, K.Malek, L.Mankiewicz, M.Molak, K.Nawrocki, L.W.Piotrowski, D.Rybka, M.Sokolowski, J.Uzycki, G.Wrochna, A.F.Zarnecki on behalf of "Pi of the Sky" collaboration http://grb.fuw.edu.pl "Pi of the Sky" apparatus observed the position of GRB080805. Three 10s images of this field have been taken at 07:37:45 - 07:38:42 ( 3 minutes before the GRB). No new object is seen within the error box and the limit is 12.5 magnitudo. After receiving the trigger from SWIFT, the field was observed 84s after the GRB. No new object has been found within the Swift-BAT error box. The limiting magnitude (unfiltered) on single 10s exposures is : 07:42:58 - 07:43:08 - 12.2 mag 07:43:11 - 07:43:21 - 12.2 mag 07:43:24 - 07:43:34 - 12.2 mag and 12.5 mag on 20 coadded images. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8068 SUBJECT: GRB 080805, Swift-BAT refined analysis DATE: 08/08/05 17:26:52 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), C. Pagani (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (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+302 sec from recent telemetry downlinks, we report further analysis of BAT GRB 080805 (trigger #319036) (Pagani, et al., GCN Circ. 8059). The BAT ground-calculated position is RA, Dec = 314.231, -62.433 deg, which is RA(J2000) = 20h 56m 55.3s Dec(J2000) = -62d 25' 58.8" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a FRED-like peak starting at ~T-5sec, peaking at ~T+3 sec, and ending at ~T+140 sec. T90 (15-350 keV) is 78 +- 7 sec (estimated error including systematics). The time-averaged spectrum from T-6.1 to T+93.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.53 +- 0.07. The fluence in the 15-150 keV band is 2.5 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.62 sec in the 15-150 keV band is 1.1 +- 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/319036/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8071 SUBJECT: GRB 080805: Swift/UVOT Upper Limits DATE: 08/08/05 22:48:54 GMT FROM: Paul Ward at MSSL P. Ward (MSSL-UCL) and C. Pagani (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 080805 starting 74 s after the BAT trigger (Pagani et al., GCN Circ. 8059). We do not find a source in any of the UVOT observations inside the XRT error circle or at the position reported by Kruehler et al. (GCN 8060). The 3-sigma upper limits for detecting a source are: Filter T_start T_stop Exp Mag White 76 175 98.5 > 20.70 White 5473 18024 1082 > 22.12 v 182 6083 332 > 19.81 b 5268 17112 1082 > 21.43 u 5061 5260 197 > 20.11 uvw1 4856 5055 197 > 19.99 uvm2 4650 6267 371 > 20.09 uvw2 5680 18053 219 > 20.12 The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627). No correction has been made for the expected extinction corresponding to E(B-V) of 0.043 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8072 SUBJECT: GRB 080805: Swift-XRT Refined Analysis DATE: 08/08/06 03:27:50 GMT FROM: Claudio Pagani at PSU/Swift-XRT C. Pagani, J. Racusin and D. Grupe (PSU) report on behalf of the Swift-XRT team: We have analysed the first four orbits of Swift-XRT data for GRB 080805 (Pagani et al., GCN 8059) beginning at T0+71 s until T0+23.1 ks. Using 728 s of XRT Photon Counting mode data and 2 UVOT images, 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 = 314.22312, -62.44479 which is equivalent to: RA (J2000): 20 56 53.55 Dec (J2000): -62 26 41.2 with an uncertainty of 2.6 arcsec (radius, 90% confidence). The XRT lightcurve shows an initial flare and a steep decay followed by a shallower phase. The decaying lightcurve can be fit with a broken power-law with an initial decay index of 3.5+/-0.3, a break at approximately T0+500 seconds and a later decay index of 0.9+/-0.3. The spectrum of the Windowed Timing mode data from the first orbit can be fit by an absorbed power-law with a photon index of 1.3+/-0.1 and absorption consistent with the Galactic value along the line of sight (3.5e20 cm^-2, Kalberla et al. 2005). The average observed (unabsorbed) flux of the WT mode data is 1.7e-9 (1.9e-10) ergs cm^-2 s^-1. Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10.0 keV XRT count rate of 0.003 counts/s at T+24hr, which corresponds to an observed flux of 1.5e-13 ergs cm^-2 s^-1. This Circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8076 SUBJECT: GRB 080805: Faulkes Telescope South optical observations DATE: 08/08/06 20:03:48 GMT FROM: Cristiano Guidorzi at INAF-OAB C. Guidorzi (INAF-OAB), I. Steele and R.J. Smith (LJMU) on behalf of a larger collaboration report: On 2008 August 05 (10:12:35 UT) we began observing the field of GRB 080805 (Pagani et al. GCN Circ. 8059) with the Faulkes Telescope South using the R and i' filters. In our coadded i' frame we marginally detect the optical afterglow (Kruehler et al. GCN Circ. 8060; de Ugarte Postigo et al. GCN Circ. 8061): Telescope Filter T_mid[hr] Exposure[s] Mag ----------------------------------------------------------- FTS i' 5.410 6x300 22.5 +/- 0.4 ----------------------------------------------------------- The calibration was performed using the I magnitudes of several USNOB-1 catalogue field objects. From the comparison with the value reported by GROND (Kruehler et al. GCN Circ. 8060) we estimate an average power-law decay index of ~0.7, consistent with that inferred in the R band (de Ugarte Postigo et al. GCN Circ. 8061). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8077 SUBJECT: GRB 080805: VLT redshift update DATE: 08/08/08 18:23:14 GMT FROM: Pall Jakobsson at U Hertfordshire P. Jakobsson (U. Hertfordshire), J. P. U. Fynbo, P. M. Vreeswijk (DARK/NBI) and A. de Ugarte Postigo (ESO) report on behalf of a larger collaboration: We have reduced the VLT spectra presented in Jakobsson et al. (GCN 8062) with new calibration files and performed a thorough line search in all four grisms (300V, 1028z, 1200R, 1400V) covering approximately 3700-9500 A. We confirm the existence of a line system at redshift z = 1.505 +/- 0.001 displaying Fe II (2382,2586,2600), the Mg II doublet (2796,2803) and Mg I (2852). In addition, there is a clear bump (flux decrease) present between 5300-5600 A that can be interpreted as the 2175 A extinction feature at z ~ 1.5. Apart from the z = 1.20 redshift system presented in GCN 8062, no other significant lines are visible. We therefore conclude that z = 1.505 is the redshift of GRB 080805.