//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8169 SUBJECT: GRB 080903: Swift detection of a burst DATE: 08/09/03 01:38:31 GMT FROM: David Burrows at PSU/Swift D. Grupe (PSU), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 01:12:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080903 (trigger=323542). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 86.797, +51.326 which is RA(J2000) = 05h 47m 11s Dec(J2000) = +51d 19' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a broad single-peaked structure with a duration of about 50 sec. The peak count rate was 1250 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 01:13:21.8 UT, 58.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 86.79071, 51.26363 which is equivalent to: RA(J2000) = 05h 47m 9.77s Dec(J2000) = +51d 15' 49.1" with an uncertainty of 3.0 arcseconds (radius, 90% containment). This location is 224 arcseconds from the BAT onboard position, outside the on-board BAT error circle, but within the BAT ground-calculated 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 1.67e+21 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 1.80e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 400 seconds with the V filter starting 75 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 3-sigma upper limit at the location of the XRT candidate is 19.4 mag. No correction has been made for the expected extinction of about 0.7 magnitudes. 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: 8170 SUBJECT: GRB 080903: ROTSE-III Optical Limits DATE: 08/09/03 02:12:02 GMT FROM: Fang Yuan at ROTSE F. Yuan (U Mich), W. Rujopakarn (Steward), H. Swan (U Mich), D.A. Smith (Guilford), T. Guver (U Arizona) report on behalf of the ROTSE collaboration: ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, responded to GRB 080903 (Swift trigger 323542; Grupe et al., GCN 8169), producing images beginning 6.7 s after the GCN notice time. An automated response took the first image at 01:12:47.7 UT, 24.4 s after the burst, and during the gamma-ray emission, under fair conditions. We took 10 5-sec, 10 20-sec and 30 60- sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or the XRT error circle, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 16.5-17.7; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 01:12:47.7 01:14:55.9 128 17.7 24.4 Y 01:15:04.6 01:19:42.4 277 18.3 161.3 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8171 SUBJECT: GRB 080903: TAROT Calern observatory optical observations DATE: 08/09/03 03:45:24 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 080903 detected by SWIFT (trigger 323542) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 29.1s after the GRB trigger (11.4s after the notice). The elevation of the field increased from 38 degrees above horizon and weather conditions were excellents. The date of trigger : t0 = 2008-09-03T01:12:23.3 The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT at the XRT position provided by Grupe et al. (GCNC 8169): t0+29.1s to t0+89.1s : R > 17.1 The second image is 30.0s exposure in tracking mode: t0+95.9s to t0+125.9s : R > 18.2 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=160.7489 lat=+11.6608 and the galactic extinction in R band is 0.6 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8172 SUBJECT: GRB 080903: Optical afterglow candidate DATE: 08/09/03 03:58:28 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo (ESO, Chile), A.J. Castro-Tirado, V. Casanova, J. Gorosabel, M. Jelinek, M. Guerrero (IAA-CSIC, Granada) report on behalf of a larger collaboration: We have observed the field of GRB 080903 (Grupe et al., GCN 8169) using the 1.5m OSN telescope at Sierra Nevada Observatory (Granada) in V, R and I bands begining at 02:30 UT (78 min after the burst). We detect a source of I~21.0 on the edge of the XRT error box at the following coordinates (J2000 +/- 0.5"): R.A.: 05:47:10.08 Dec.: +51:15:50.9 Further observations are ongoing from OSN and NOT to check the colour and variability of this source. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8173 SUBJECT: GRB 080903: Astrotel-Caucasus optical observations DATE: 08/09/03 05:40:54 GMT FROM: Denis Denissenko at IKI, Moscow S. Korotkiy (Ka-Dar Observatory), T. Kryachko, B. Satovskiy (Astrotel Observatory, KSU/AST) and D. Denisenko (IKI) report: We have observed the error box of Swift gamma-ray burst GRB 080903 (Grupe et al., GCN 8169) with 0.3-m f/7.8 Astrotel-Caucasus telescope (+ Apogee Alta U9000 CCD camera) at Kazan State University Mountain Station (Karachay-Cherkessia, Russia). The first 120-sec unfiltered exposure was taken at 01:18:21 UT, 358 seconds after the burst trigger. Inside the XRT error circle we have found a new source not present on DSS plates at the following coordinates (J2000.0): 05 47 10.05 +51 15 50.9 (astrometry relative to USNO-A2.0 catalogue, accuracy +/-0.2"). Using the nearby USNO-A2.0 1350-06155883 (05 47 16.36 +51 15 56.4) with R=18.1 as a comparison star, we have measured CR (unfiltered with Red zero point) magnitude 19.1 for the afterglow candidate. The limiting magnitude of the image is 20.5. Four additional images were obtained with the approaching twilight and brightening sky background. The object is still present on the second 120-sec exposure obtained at 01:22:09 UT, but not detected on the next images. The crop of Astrotel-Caucasus image is available at: http://www.astroalert.su/files/grb080903_crop_x4_size.jpg Color-combined (BRIR) DSS image of the same area for comparison: http://hea.iki.rssi.ru/~denis/GRB080903-BRIR-crop.jpg //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8174 SUBJECT: GRB 080903: Liverpool Telescope observations DATE: 08/09/03 09:10:06 GMT FROM: Cristiano Guidorzi at INAF-OAB C. Guidorzi (INAF-OAB), R. J. Smith (LJMU), A. Gomboc (U. Ljubljana) on behalf of a larger collaboration report: On 2008 September 03 (03:32:18 UT) we began observing the field of GRB 080903 (Grupe et al. GCN Circ. 8169) with the Liverpool Telescope using the SDSS i filter. We clearly detect the optical afterglow candidate reported by de Ugarte Postigo et al. (GCN Circ. 8172) and Korotkiy et al. (GCN Circ. 8173). We found the following magnitudes: Telescope Filter T_mid[hr] Exposure[s] Mag ------------------------------------------------------------- LT i' 2.59 6x300 21.32 +/- 0.07 LT i' 4.08 6x300 21.52 +/- 0.11 ------------------------------------------------------------- The calibration was performed using the I magnitude of the following nearby USNOB1 catalogue star: 05:47:14.30, +51:15:32.8, using I=14.77. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8175 SUBJECT: GRB 080903: optical observations DATE: 08/09/03 12:39:23 GMT FROM: Alexei Pozanenko at IKI, Moscow Andreev M., Sergeev A., Karpov N. (Terskol Branch of Institute of Astronomy), Khramtsova M. (The Ural State University), Petkov V.(BNO INR RAS), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed the field of GRB 080903 (Grupe et al. GCN 8169) with Z-600 and Celestron 11" telescopes of Mt. Terskol observatory. A set of 60 s exposures in R filter was taken with Z-600 starting 22 minutes after burst onset. In a combined image we clearly detect afterglow candidate (Ugarte Postigo et al. GCN 8172, Korotkiy et al. GCN 8173). Preliminary photometry is based on USNO-A2.0 1350-06155883 star (05 47 16.36 +51 15 56.4) assuming R=18.1: T0+ Exp. R_mag (Mid) 1673 sec. 10x60 sec. 19.35 +/-0.2 The afterglow is also detected in unfiltered combined image (40x10s) taken with Celestron 11" telescope at Tmid = 1280 s. The photometry is underway. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8176 SUBJECT: GRB 080903, Swift-BAT refined analysis DATE: 08/09/03 14:25:14 GMT FROM: Scott Barthelmy at NASA/GSFC J. Tueller (GSFC), 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), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+723 sec from recent telemetry downlinks, we report further analysis of BAT GRB 080903 (trigger #323542) (Grupe, et al., GCN Circ. 8169). The BAT ground-calculated position is RA, Dec = 86.790, 51.256 deg, which is RA(J2000) = 05h 47m 09.6s Dec(J2000) = +51d 15' 22.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a single FRED peak starting at ~T-5 sec and ending at ~T+80 sec. There appears to be very low level emission out to ~T+500 sec. T90 (15-350 keV) is 66 +- 11 sec (estimated error including systematics). The time-averaged spectrum from T-10.5 to T+68.0 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.84 +- 0.52, and Epeak of 60 +- 15 keV (chi squared 63 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T-2.46 sec in the 15-150 keV band is 0.8 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.72 +- 0.10 (chi squared 73 for 57 d.o.f.). 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/323542/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8177 SUBJECT: GRB 080903: Enhanced Swift-XRT position DATE: 08/09/03 15:05:26 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 3613 s of XRT Photon Counting mode data and 3 UVOT images for GRB 080903, 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 = 86.79206, +51.26433 which is equivalent to: RA (J2000): 05h 47m 10.10s Dec (J2000): +51d 15' 51.6" with an uncertainty of 1.6 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: 8178 SUBJECT: GRB 080903: Swift-XRT Refined Analysis DATE: 08/09/03 18:02:51 GMT FROM: Dirk Grupe at PSU/Swift-XRT Dirk Grupe (PSU) and Phil Evans (U Leicester) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 080903 (trigger=323542; Grupe et al., GCN Circ 8169) at 01:13:21.8 UT, 58.5 seconds after the BAT trigger. The enhanced XRT position given in GCN Circ 8177 (Goad et al) is 30.3" away from the ground-processed BAT position given in GCN Circ. 8176 (Tueller et al.), consistent with that position. The 0.3-10 keV X-ray light curve starts at a level of 2e-9 ergs/s/cm2 (40 counts/s) in the XRT with a rather flat decay slope at these early times of alpha = 1.00+/-0.04. The light curve breaks at about 1 ks after the burst and steepens dramatically to alpha = 2.47+/-0.14. If this decay slope continues as is, we predict an XRT count rate at T0+24 hours of 3e-5 counts/s or 2e-15 ergs/s/cm2, so undetectable for XRT. The spectrum of the Windowed Timing data of the first orbit can be fitted by an absorbed single powerlaw with an unusual flat photon index Gamma = 0.94 +/- 0.06 and column density fixed to the Galactic value of 1.67e21 cm-2 in the direction of the burst. This photon index is consitent with that found by the BAT in the 15-150 keV band (Gamma=0.84+/-0.52; Tueller et al., GCN Circ. 8176). The spectrum becomes slightly steeper at later times. The Photon Counting mode data show an photon spectral slope of Gamma=1.23+/-0.16 with the absorption column density fixed to the Galactic value. This Circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8179 SUBJECT: GRB 080903: Swift/UVOT Observations DATE: 08/09/03 19:06:16 GMT FROM: Frank Marshall at GSFC F.E. Marshall (NASA/GSFC) and D. Grupe (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 080903 starting 75 s after the BAT trigger (Grupe et al., GCN Circ. 8169). A source is detected in the initial exposure in the V filter at the position of the optical afterglow (de Ugarte Postigo et al., GCN Circ. 8172). There is also a marginal (1.8 sigma) detection in the initial exposures with the U filter. A valid detection in the U filter would indicate a redshift of less than 3.3. The magnitudes and 3-sigma upper limits in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for detecting a source in the first finding chart (FC) exposure and subsequent co-added exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag v (FC) 75 475 393 19.8 +/- 0.24 v 595 28705 2596 >21.5 b 555 12429 1307 >21.8 u 530 829 58 20.0 +/- 0.47 u 4906 34528 3049 >21.8 uvw1 506 7268 551 >21.0 uvm2 481 7160 655 >20.7 uvw2 571 6750 452 >21.2 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.22 in the direction of the burst (Schlegel et al. 1998).