//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5544 SUBJECT: GRB 060908: Swift detection of a burst with a bright optical counterpart DATE: 06/09/08 09:16:22 GMT FROM: Scott Barthelmy at NASA/GSFC P. A. Evans (U Leicester), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), O. Godet (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU), A. N. Morgan (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-OAB), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 08:57:22 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060908 (trigger=228581). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 31.835, +0.370 {02h 07m 20s, +00d 22' 14"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows 3 overlapping peaks starting at ~T-10 sec and then a 4th peak lasting until T+12 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~T+2 sec after the trigger. The XRT began observing the field at 08:58:34 UT, 72 seconds after the BAT trigger. XRT found a fading and uncatalogued X-ray source located at RA(J2000) = 02h 07m 18.1s, Dec(J2000) = +00d 20' 29.1", with an estimated uncertainty of 3.8 arcseconds (90% confidence radius). This location is 108 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 5.0e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 80 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at (RA,DEC) (J2000) of (31.8265,0.3420) or (02h07m18.36s,+00o20'31.2") with a 1-sigma error radius of about 0.7 arc sec. This position is 3.8 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.1 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 0.03. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5545 SUBJECT: GRB 060908: PROMPT Detection of a Bright Counterpart DATE: 06/09/08 09:29:08 GMT FROM: Melissa Nysewander at UNC,Chapel Hill M. Nysewander, D. Reichart, K. Ivarsen, A. Foster, A. LaCluyze, J.A. Crain, report: SkyNet observed the localization of GRB 060908 with four of the PROMPT telescopes starting at 08:58:25 UT. We note a very bright uncatalogued rapidly fading source at approximately 02:07:19, +00:20:30. In the r' initial image beginning at 08:59:07 UT, 105 s after the trigger, the source is at approximately r ~ 15. Further analysis is underway. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5546 SUBJECT: GRB 060908: REM optical prompt observation DATE: 06/09/08 11:27:09 GMT FROM: Angelo Antonelli at Obs. Astro. di Roma L.A. Antonelli, S. Covino, V. Testa, E. Palazzi, E. Molinari, P. D'Avanzo, G. Chincarini, F.M. Zerbi, G. Tosti, F. Vitali, P. Conconi, G. Cutispoto, G. Malaspina, L. Nicastro, E. Meurs, and P. Goldoni report on behalf of the REM/ROSS team: The robotic 60-cm REM telescope, located at La Silla (Chile), observed automatically the field of GRB 060908 (Evans et al., GCN 5544) with ROSS optical camera. Observations started at 09:06:21 UT, about 7 min after the burst, in R, I and V band. An uncatalogued fading source was observed in all filters at: RA: 02:07:18.3 DEC +00:20:31 This position is consistent with the one reported in GCN 5544 and GCN 5545. In the R initial image the source is at approximately R ~ 17 in 20 sec exposure time. Further analysis is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5550 SUBJECT: GRB 060908 - SDSS Pre-burst Observations DATE: 06/09/08 14:23:47 GMT FROM: Richard J. Cool at U.of AZ/Steward Obs Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL), J. Brinkmann (APO), Donald Q. Lamb (Chicago), Donald P. Schneider (PSU), and Daniel E. Vanden Berk (PSU) report: The Sloan Digital Sky Survey (SDSS) imaged the field of burst GRB060908 prior to the burst. As these data should be useful as a pre-burst comparison and for calibrating photometry, we are supplying the images and photometry measurements for this GRB field to the community. Data from the SDSS, including 5 FITS images, 3 JPGS, and 3 files of photometry and astrometry, are being placed at http://mizar.as.arizona.edu/~grb/public/GRB060908 We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=31.8350 (02:07:20.4), dec=0.370000 (00:22:12.0); Swift-BAT TRIGGER 228581), as well as 3 gri color-composite JPGs (with different stretches). The units in the FITS images are nanomaggies per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie is a flux-density unit equal to 10^-9 of a magnitude 0 source or, to the extent that SDSS is an AB system, 3.631e-6 Jy. The FITS images have WCS astrometric information. In the file GRB060908_sdss.calstar.dat, we report photometry and astrometry of 37 bright stars (r<20.5) within 15' of the burst location. The magnitudes presented in this file are asinh magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118, 1406). Beware that some of these stars are not well-detected in the u-band; use the errors and object flags to monitor data quality. In the files GRB060908_sdss.objects_flux.dat and GRB060908_sdss.objects_magnitudes.dat, we report photometry of 1285 objects detected within 6' of the GRB position. We have removed saturated objects and objects with model magnitudes fainter than 23.0 in the r-band. The fluxes listed in GRB060908_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB060908_sdss.objects_magnitudes.dat are asinh magnitudes. All quantities reported are standard SDSS photometry, meaning that they are very close to AB zeropoints and magnitudes are quoted in asinh magnitudes. Photometric zeropoints are known to about 2% rms. None of the photometry is corrected for dust extinction. The Schlegel, Finkbeiner, and Davis (1998) predictions for this region are A_U=0.146 mag, A_g=0.107 mag, A_r = 0.078 mag, A_i=0.059 mag, and A_z=0.042 mag. The file GRB060908_sdss.spectro.dat contains a list of the 11 objects with SDSS spectroscopy within 6 arcminutes of the GRB position. In addition to the redshift and 1-sigma error for each object, this file also lists the object spectroscopic classification. SDSS astrometry is generally better than 0.1 arcsecond per coordinate. Users requiring high precision astrometry should take note that the SDSS astrometric system can differ from other systems such as those used in other notices; we have not checked the offsets in this region. More detailed information pertaining to our SDSS GRB releases can be found in our initial data release paper (Cool et al. 2006, astro-ph/0601218). See the SDSS DR4 documentation for more details: http://www.sdss.org/dr5. These data have been reduced using a slightly different pipeline than that used for SDSS public data releases. We cannot guarantee that the values here will exactly match those in the data release in which these data are included. In particular, we expect the photometric calibrations to differ by of order 0.01 mag. This note may be cited, but please also cite the SDSS data release paper, Adelman-McCarthy et al. (2006, ApJS, 162, 38), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5551 SUBJECT: GRB 060908, Swift-BAT refined analysis DATE: 06/09/08 14:27:06 GMT FROM: Scott Barthelmy at NASA/GSFC D. Palmer (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMD), P. A. Evans (U Leicester), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of 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 060908 (trigger #228581) (Evans, et al., GCN Circ. 5544). The BAT ground-calculated position is RA,Dec = 31.820, 0.330 deg {2h 7m 16.8s,+0d 19' 48.9"} (J2000) +- 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 46%. The lighcurve has 3 overlapping peaks starting at ~T-12 sec then briefly returning to background at T+6 sec. The second peak has a maximium at T+10 sec and ends at T+14 sec. T90 (15-350 keV) is 19.3 +- 0.3 sec (estimated error including systematics). The time-averaged spectrum from T-17.5 to T+15.1 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.33 +- 0.07. The fluence in the 15-150 keV band is 2.9 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.97 sec in the 15-150 keV band is 3.2 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5552 SUBJECT: GRB 060908: Danish/DFOSC optical observations DATE: 06/09/08 14:29:17 GMT FROM: Evert Rol at U.Leicester K. Wiersema (University of Amsterdam), C.C. Thoene (DARK Cosmology Centre) and E. Rol (University of Leicester) report: We observed the position of GRB 060908 using the Danish 1.5m telescope equipped with DFOSC, in R band. The optical transient (Evans et al, GCN 5544) is detected in all our exposures. We performed photometry with respect to a nearby USNO-B1.0 star 0903-0022606, for which we assume R = 18.29. The reported error in our magnitude is therefore only the error in the photometry of the transient. We find R = 21.57 +/- 0.04, 46 minutes after the trigger. During our observations between 36 and 70 minutes after the trigger, the optical transient is clearly decaying: a power law fit to our data results in a decay index of 1.07 +/- 0.11. The magnitude and decay rate suggest that the decay slowed down somewhat, after an initial steep decline. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5553 SUBJECT: GRB 060908: Swift/UVOT Observations DATE: 06/09/08 15:14:26 GMT FROM: Adam Morgan at PSU/Swift-UVOT A. N. Morgan (PSU), D. E. Vanden Berk (PSU), P. Brown (PSU) and P. A. Evans (U Leicester) report on behalf of the Swift UVOT team: The Swift/UVOT began observations of GRB 060908 at 08:58:42 UT, ~80 seconds after the initial Swift BAT trigger (Evans et al., GCN Circ. 5544). An optical counterpart was detected with the V filter at a position RA(J2000) = (02h 07m 18.36s,+00d 20' 31.2") to within 0.7". An optical afterglow was detected in the White, V, B, U, and UVW1 filters. The best estimate for the photometric redshift is z=1.62 assuming an SMC extinction law with E(B-V)=0.05, but it is poorly constrained. Values range from z=0.26-2.20 for a 90% confidence range. The photometry was performed using a 6 arcsec radius aperture and is reported below: Filter T_range(s) Exp. (s) Magnitude White 80-179 99.8 15.06 +/- 0.03 White 5839-6038 199.8 19.57 +/- 0.22 V 185-584 399.8 16.85 +/- 0.05 V 4816-6448 399.6 19.44 +/- 0.36 B 663-820 19.6 18.41 +/- 0.31 B 5635-7129 262.5 > 20.03 (3.0-sigma) U 639-658 19.7 17.01 +/- 0.16 U 786-805 19.8 17.99 +/- 0.32 UVW1 615-782 39.6 18.61 +/- 0.35 UVW1 5226-6857 399.6 > 20.24 (3.0-sigma) UVM2 591-758 39.6 > 18.57 (3.0-sigma) UVM2 5021-6652 399.6 > 20.54 (3.0-sigma) UVW2 691-858 39.6 > 19.07 (3.0-sigma) UVW2 4612-6243 399.6 > 20.71 (3.0-sigma) The values quoted above are not corrected for the expected Galactic extinction of E(B-V)=0.03. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5554 SUBJECT: GRB 060908, Swift/XRT refined analysis DATE: 06/09/08 15:29:25 GMT FROM: Phil Evans at U of Leicester P.A. Evans, A.P. Beardmore, O. Godet and K.L. Page (U. Leicester) report on behalf of the Swift/XRT team: We have analysed the first 2 orbits of Swift data of GRB 060908 (Evans et al., GCN 5544), totalling 100 s of data in Window Timing mode (WT) and 2.5 ks in Photon Counting mode (PC). The PC mode image provides a refined XRT position of RA(J2000) = 02 07 18.21 Dec(J2000) = +00 20 28.8 with an error of 3.6" (90% confidence). This position is within 1.5" of the initial XRT position, and 3.4" from the UVOT position, reported in GCN 5554. Spectral fits to the first orbit of data suggest an absorption column in excess of the Galactic value (2.4e20 cm^-2). The WT data yielded 8.0+4.9/-4.0 e20 cm^-2 and the PC mode data gave 6.4+3.4/-3.0 e20 cm^-2. There is also evidence for spectral evolution during the first orbit: the WT mode photon index was 2.43 (+0.30, -0.26), while the PC mode photon index was 1.95 (+0.15,-0.14). The observed PC mode flux was 7.5e-11 erg/s/cm^2 during the first orbit; which translates to an unabsorbed flux of 8.9e-11 erg/s/cm^2 The lightcurve of the first 2 orbits (T0+78 to T0+6600) can be modelled with a single power-law, and a flare at around 800s. The decay slope is 1.11 +/-0.06, and we thus predict a count rate of 0.004 counts per second 24 hours after the trigger. This translates to a flux of 1.56e-13 erg/s/cm^2, or an unabsorbed flux of 1.85e-13 erg/s/cm^2. This circular is an official product of the Swift XRT Team. -- ------------------------- Phil Evans, PDRA/Swift Scientist X-ray and Observational Astronomy Group, University of Leicester Tel: (0116) 252 5059 pae9@star.le.ac.uk http://www.astro.keele.ac.uk/~pae //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5555 SUBJECT: GRB 060908: redshift DATE: 06/09/08 23:48:02 GMT FROM: Evert Rol at U.Leicester E. Rol (U of Leicester), P. Jakobsson (U of Hertfordshire), N. Tanvir (U of Leicester), A. Levan (U of Hertfordshire), report for a larger collaboration: We obtained a spectrum of GRB 060908 (Evans et al, GCN 5544) with Gemini-North/GMOS, for a total of 30 minutes starting approximately 2 hours post burst. We identify absorption lines of CIV (1548, 1551) and SiII (1304), and possibly AlIII (1863), at a redshift of z = 2.43 +/- 0.05. We thank the Gemini staff for their support with the observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5556 SUBJECT: VLA observations of GRB 060908 DATE: 06/09/10 04:12:23 GMT FROM: Poonam Chandra at U Virginia/NRAO P. Chandra (UVA/NRAO) and D. A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration: "We observed the field centered on the BAT position of the Swift burst GRB 060908 (GCN#5544) using the VLA at a frequency of 8.46 GHz and starting at 7.55 UT on Sept 1st, a day after the burst. There is no detection of the GRB with 2-sigma upper limit of 51 microJy. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5653 SUBJECT: GRB060908: optical observations DATE: 06/09/29 14:58:49 GMT FROM: Alexei Pozanenko at IKI, Moscow M. Andreev, A. Sergeev (Terskol Branch of Institute of Astronomy), A. Kurenya (Baksan Neutrino Observatory), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed the afterglow of GRB060908 (Evans et al., GCN 5544) with 2m telescope of Terskol Observatory on Sep. 08 (UT) 20:51:45 - 21:14:45. We detect the afterglow on a combined image of 20x60 s exposure. Based on USNO A2.0 field stars we estimate brightness of the optical transient: Mid time (UT), Exposure, R_mag Sep. 08.877 20x60 s 20.70 +/- 0.27 It should be noted that R magnitude of the star (USNO-B1.0 0903-0022606 R = 18.29) used in GCN 5552 (Wiersema et. al) is inconsistent with the R-magnitude of the same star USNO A2.0 (0900-00494220 R = 14.9). R-magnitudes of other field stars of the two catalogs USNO-B1.0 and USNO A2.0 are also inconsistent by ~2.9 mag in average. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5674 SUBJECT: GRB 060908: Detection of a possible host DATE: 06/10/01 17:35:50 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr Christina C. Thoene (DARK Cosmology Centre), Christina Henriksen (DARK, NOT) and Klaas Wiersema (Univ. of Amsterdam) report: We observed the field of GRB060908 on Sep. 21 and 23 with ALFOSC at the NOT on La Palma in V, R and i under variable conditions. Near the position of the afterglow (GCN 5544), we detect a faint, extended source in stacked images in V (7x600s) and R (10x600s), which we assume to be the host galaxy of GRB060908. The possible host is not visible in 7x600s stacked images in the i band which might be due to severe fringing in the i band images. Photometry of the source gives values of V=24.9 +-0.1, R=25.12 +-0.05 and i>24.6 +-0.2 using photometric zeropoints from the NOT/ALFOSC webpage. An image of the host in the R-band can be found at www.astro.ku.dk/~cthoene/GRBs/