/////////////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8186 SUBJECT: GRB 080906: Swift detection of a burst with optical afterglow DATE: 08/09/06 13:52:03 GMT FROM: David Burrows at PSU/Swift L. Vetere (PSU), S. D. Barthelmy (GSFC), P. J. Brown (PSU), D. N. Burrows (PSU), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (CRESST/GSFC/USRA), J. Mao (INAF-OAB), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), J. L. Racusin (PSU), B. Sbarufatti (INAF-IASFPA), M. Stamatikos (NASA/ORAU), G. Tagliaferri (INAF-OAB), E. Troja (INAF-IASFPA) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 13:33:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080906 (trigger=323984). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 227.890, -80.486 which is RA(J2000) = 15h 11m 34s Dec(J2000) = -80d 29' 09" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed one major peak of duration ~50 sec, with possible smaller peaks. The peak count rate was ~2000 counts/sec (15-350 keV), at ~10 sec after the trigger. The XRT began observing the field at 13:34:27.6 UT, 71.3 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 228.0514, -80.5183 which is equivalent to: RA(J2000) = 15h 12m 12.3s Dec(J2000) = -80d 31' 05.8" with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 150 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 82 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 15:12:10.63 = 228.0443 DEC(J2000) = -80:31:04.1 = -80.5178 with a 1-sigma error radius of about 0.5 arc sec. This position is 4.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.7 with a 1-sigma error of about 0.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.30. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8194 SUBJECT: GRB 080906: GROND observations of the optical/NIR afterglow DATE: 08/09/07 09:44:25 GMT FROM: Paulo M. J. Afonso at MPE GRB 080906: GROND observations of the optical/NIR afterglow P.Afonso, T. Kruehler, J. Greiner, C.Clemens, A. Yoldas (all MPE Garching) and A. Kuepcue Yoldas (ESO) report on behalf of the GROND team: We observed the field of GRB 080906 (Swift trigger 323984; L. Vetere et al., GCN #8186), simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 00:12 UT on September 7th, 2008, 10.7 hrs after the GRB trigger.We detect the optical afterglow reported by L. Vetere et al. (GCN #8186) at a position consistent with the UVOT detection in all bands, implying a redshift smaller than 3.5. Preliminary photometry yields the following magnitudes calibrated against USNO-B1 and 2MASS field stars in stacked images: Band Exp(min) Mag g' 24 22.2 +- 0.1 r' 24 21.4 +- 0.1 i' 24 21.2 +- 0.1 z' 24 21.2 +- 0.1 J 20 20.2 +- 0.1 H 20 19.2 +- 0.1 K 20 18.5 +- 0.1 not corrected for the expected Galactic foreground reddening of E(B-V) = 0.30 mag (Schlegel et al., 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8196 SUBJECT: GRB 080906, Swift-BAT refined analysis DATE: 08/09/07 17:40:23 GMT FROM: Scott Barthelmy at NASA/GSFC M. Stamatikos (GSFC/ORAU), 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), D. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. Ukwatta (GWU), L. Vetere (PSU) (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 080906 (trigger #323984) (Vetere, et al., GCN Circ. 8186). The BAT ground-calculated position is RA, Dec = 228.055, -80.540 deg, which is RA(J2000) = 15h 12m 13.3s Dec(J2000) = -80d 32' 24.9" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 58%. The mask-weighted light curve shows a roughly symmetrical peak starting at ~T-100 sec, peaking around T+10 sec, and tailing off to about T+100 sec. T90 (15-350 keV) is 147 +- 21 sec (estimated error including systematics). The time-averaged spectrum from T-105 to T+104 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.59 +- 0.09. The fluence in the 15-150 keV band is 3.5 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.06 sec in the 15-150 keV band is 1.0 +- 0.2 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/323984/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8197 SUBJECT: GRB 080906: Swift-XRT Refined Analysis DATE: 08/09/07 20:20:43 GMT FROM: Loredana Vetere at PSU L. Vetere, J.L. Racusin, C. Pagani (PSU), J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 080906 (trigger=323984; Vetere et al., GCN Circ 8186) at 13:34:27.6 UT, 71.3 seconds after the BAT trigger. Using 1224 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 to the USNO-B1 catalogue): RA, Dec = 228.04211, -80.51787 which is equivalent to: RA (J2000): 15 12 10.11 Dec (J2000): -80 31 04.3 with an uncertainty of 1.8 arcsec (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 position is 80 arcsec away from the ground-processed BAT position given in GCN Circ. 8196 (Stamatikos et al.) inside BAT error circle. The WT mode lightcurve shows a number of flares, with the strongest peaking around 186, 598 and 907 s after the trigger. The PC data in later orbits shows some flaring activity and decays as a single power-law with alpha = 1.25 +/- 0.11. The WT spectrum of the first 80 s (before the first peak) can be fitted with a power-law of Gamma = 1.82 +/-0.08 and absorption consistent with the Galactic value along the line of sight (9.7x10^20 cm^-2). The observed (unabsorbed) flux over this time is 1.98 (2.7)x10^-9 erg cm^-2 s^-1. A spectrum extracted from the PC mode data (11.6-75.6 ks after the trigger) can be fitted with a power-law of Gamma = 2.3 +0.1/-0.2 and total NH = (1.7 +/- 0.5)x10^22 cm^-2, slightly in excess of the Galactic value. The observed (unabsorbed) flux over this time is 1.7 (3.1)x10^-11 erg cm^-2 s^-1. If the decay continues with alpha = 1.25, the predicted count-rate at 48 hours is 0.007 count s^-1, corresponding to an observed (unabsorbed) flux of 2.6 (4.8)x10^-13 erg cm^-2 s^-1. This Circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8198 SUBJECT: GRB 080906: Refined Swift/UVOT Observations DATE: 08/09/07 22:00:22 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/USRA/GSFC) & L. Vetere (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 080906 starting 62 s after the BAT trigger (Vetere et al., 2008, GCNC. 8186). Settled observations started at T + 82 s. We detect the optical afterglow (Vetere et al., GCNC 8186) in the v, b, u, and white filters. The refined UVOT source position is RA (J2000.0) = 15:12:10.65 Dec (J2000.0) = -80:31:03.2 with an estimated uncertainty of 0.64 arcsec (radius, 90% confidence). Magnitudes and upper limits are reported below. Filter TSTART TSTOP Exposure Mag Err Comment white 82 182 98 19.71 0.15 v 188 588 393 18.61 0.12 b 668 6204 216 21.02 0.44 u 643 5998 236 20.37 0.34 uvw1 619 5793 236 >20.9 2-sigma upper limit uvm2 594 5588 236 >20.5 2-sigma upper limit uvw2 698 6614 235 >21.1 2-sigma upper limit The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.30 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383,627). The detection in the u filter, coupled with the non-detections in the uvw1, uvm2, and uvw2 filters, are consistent with a redshift of approximately z < 2.6. The power-law decay index in the v band between 338 and 6719 s is -0.50 +/- 0.04. Please update my e-mail address in your Address Book to . / \ / //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8212 SUBJECT: GRB 080906: Refined Swift/UVOT Photometric Redshift DATE: 08/09/11 14:38:23 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC Stephen Holland (CRESST/USRA/GSFC) reports, on behalf of the Swift/UVOT team: We have performed UVOT photometry on the optical afterglow of GRB 080906 (Vetere et al., 2008, GCNC 8186) at approximately 6000 s after the BAT trigger. This data was used to estimate the photometric redshift of the afterglow assuming a reddened power-law spectrum with a Lyman cut-off. We find a best-fit value for the photometric redshift of z = 2.0 +/- 0.4 (90% confidence). Combining this redshift with the BAT fluence given in Stamatikos et al. (2008, GCNC 8196) yields a total energy of (8.4 +/- 0.5) x 10^51 erg (90% confidence) in the observed energy range 15-150 keV. The assumed cosmology is (H_0,Omega_matter,Omega_lambda) = (70,0.3,0.7). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8214 SUBJECT: GRB 080906B: Fermi GBM detection DATE: 08/09/11 16:01:22 GMT FROM: Elisabetta Bissaldi at MPE E. Bissaldi, S. McBreen and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 05:05:11 UT on 6 September 2008, the Fermi Gamma-ray Burst Monitor triggered and located GRB 080906B (trigger 242370312 / 080906212). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 185.5, Dec = -8.6 (J2000 degrees) (equivalent to J2000 12h 22m, -08d 36'), with a statistical uncertainty of 3.3 degrees (radius, 1-sigma containment; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 32 degrees. This GRB consists of one main emission phase comprising several overlapping pulses, with an estimated T90 (50-300 keV) of about 5 s. The time-averaged spectrum from T0 to T0+3.8 s is best fit by a Band function with the following parameters: alpha = -0.07 +/- 0.09 beta = -2.10 +/- 0.07 Epeak = 125.3 +/- 6.6 keV The fluence (25-1000 keV) is 10.9 (+/-0.1)E-06 erg/cm2. The peak flux (25-1000 keV) on the 128 ms timescale is 22 +/- 4 ph/s/cm2. The spectral analysis results presented above are preliminary; the final results will be published in the Fermi GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8216 SUBJECT: GRB 080906: Watcher observations DATE: 08/09/12 13:41:43 GMT FROM: Alejandro Ferrero at U College,Dublin Alejandro Ferrero (UCD School of Physics), John French (UCD School of Physics, DARK/NBI), Gary Melady (UCD School of Physics) report on behalf of a larger collaboration: The Watcher 40 cm robotic telescope at Boyden Observatory, South Africa, began imaging the field of GRB 080906 (Vetere et al. GCN 8186) at 16:51:15.5 UT, 3.6 h after the Swift triggger. We do not detect the afterglow reported by Holland et al. (GCN 8198) and Afonso et al. (GCN 8194). Our first 120s exposure has a limiting magnitude of 16.9, while a stacked sequence of 10 120s images, with an exposure mid-time of 3.8 hrs after the trigger, results in a limiting magnitude of 18.4. Unfiltered magnitudes are transformed to R-band by comparison with the USNO-B1 catalog.