//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8330 SUBJECT: GRB 081007: Swift detection of a burst with optical afterglow DATE: 08/10/07 05:41:22 GMT FROM: Wayne Baumgartner at GSFC W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), S. D. Hunsberger (PSU), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester) and M. C. Stroh (PSU) report on behalf of the Swift Team: At 05:23:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081007 (trigger=330856). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 339.976, -40.136 which is RA(J2000) = 22h 39m 54s Dec(J2000) = -40d 08' 08" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 25 sec. The peak count rate was 1500 counts/sec (15-350 keV), at 1 sec after the trigger. The XRT began observing the field at 05:25:32.1 UT, 99.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 339.96077, -40.14675 which is equivalent to: RA(J2000) = 22h 39m 50.58s Dec(J2000) = -40d 08' 48.3" with an uncertainty of 3.1 arcseconds (radius, 90% containment). This location is 57 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.38e+20 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 1.53e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 108 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 22:39:50.40 = 339.9600 DEC(J2000) = -40:08:48.8 = -40.1469 with a 1-sigma error radius of about 0.5 arc sec. This position is 2.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.0 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 0.01. Burst Advocate for this burst is W. H. Baumgartner (wayne AT milkyway.gsfc.nasa.gov). 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: 8331 SUBJECT: GRB 081007: REM NIR and optical counterpart DATE: 08/10/07 05:48:11 GMT FROM: Stefano Covino at Brera Astronomical Observatory S. Covino, L.A. Antonelli, L. Calzoletti, S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F. D'Alessio, P. D'Avanzo, F. Fiore, D. Fugazza, P. Goldoni, D. Guetta, C. Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Stratta, G. Tagliaferri, G. Tosti, V.Testa, S.D. Vergani, F. Vitali report on behalf of the REM team: The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of the GRB 081007 (Baumgartner et al. GCN 8330) starting about 35s s from the GRB alert (46s from the GRB time) with the VRIJHK bands. We detect a source with coordinates RA,DEC = (22:39:50.39,-40:08:49.1) consistent with the UVOT source at H~14.2. The source is slowly fading after the first observations. Further observations are in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8332 SUBJECT: GRB 081007, SMARTS optical/IR afterglow observations DATE: 08/10/07 06:58:55 GMT FROM: Bethany Cobb at Yale U B. E. Cobb (UC Berkeley) reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 081007 (GCN 8330, Baumgartner et al.), starting 23 minutes post-burst in BVRIJHK. In the R-band, the GRB afterglow (GCN 8330, Baumgartner et al. & GCN 8331, Covino et al.) appears to fade by approximately 0.6 magnitudes between 23 minutes and 56 minutes post-burst, indicating a decay rate of alpha = -0.6 (where afterglow flux is proportional to t^alpha). Observations of this burst are continuing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8333 SUBJECT: GRB 081007, Faulkes Telescope North optical observations DATE: 08/10/07 07:30:58 GMT FROM: James Smith at ARI,Liverpool John Moors U R.J. Smith, A. Melandri, I.A. Steele, D.F. Bersier, C.G. Mundell, (Liverpool JMU), A. Gomboc (Ljubljana), C. Guidorzi (INAF-OAB) on behalf of a larger collaboration reports: The robotic 2m Faulkes Telescope North located in Hawaii observed the field of the GRB 081007 (Baumgartner et al. GCN 8330) starting automatically as soon as the target rose above the observable horizon about 17 minutes after the GRB time. A fading optical source is detected at the XRT position reported by (Baumgartner et al. GCN 8330). Over the period from 0.2 - 1 hour after the burst, the OT is seen to fade in both R and I with a flux power law slope of -0.7. Filter Mag T_mid[min] ----------------------------- R 17.9 +/- 0.4 17.50 R 18.6 +/- 0.4 46.66 I 17.1 +/- 0.4 21.55 I 17.6 +/- 0.4 39.38 ----------------------------- The calibration was performed using the R2 and I magnitudes of the USNOB-1 catalogue field star at 22:39:43 -40:10:15.3 J2000. A equivalent amount of B-band data in which the source is detected have also been obtained and are being analysed. Further observations are ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8334 SUBJECT: GRB 081007: Enhanced Swift-XRT position DATE: 08/10/07 08:11:54 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 3344 s of XRT Photon Counting mode data and 4 UVOT images for GRB 081007, 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 = 339.96031, -40.14731 which is equivalent to: RA (J2000): 22h 39m 50.48s Dec (J2000): -40d 08' 50.3" with an uncertainty of 1.8 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: 8335 SUBJECT: GRB 081007: Gemini-south redshift DATE: 08/10/07 13:46:48 GMT FROM: Edo Berger at Princton U E. Berger (Harvard), D. B. Fox, A. Cucchiara (Penn State), and S. B. Cenko (UC Berkeley) report on behalf of a larger collaboration: "Starting on 2008 October 7.276 UT (73 min after the burst) we observed the optical counterpart of GRB 081007 (GCN 8330) using GMOS on the Gemini-South 8-m telescope. Two 900-sec exposures were obtained covering a wavlength range of 4600-7400A. We identify two absorption features at 6016.7 and 6070.3 A, as well as a weak emission line at 5700.9 A, which correspond to the CaII H&K and [OII]3727 lines at a redshift of z=0.5295+/-0.0001." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8336 SUBJECT: GRB 081007: Swift-XRT Team refined analysis DATE: 08/10/07 18:37:29 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) & W.H. Baumgartner (GSFC/UMBC) report on behalf of the Swift-XRT team: We have analysed the XRT data obtained so far for GRB 081007 (Baumgartner et al., GCN Circ. 8330), consisting of 70 s of Windowed Timing (WT) mode and 8 ks of Photon Counting mode data. The UVOT-enhanced position was given by Beardmore et al. in GCN Circ. 8334 The X-ray light-curve showed an initial steep decay with alpha = 4.0 +/- 0.2 until about 230 s after the burst, at which time the slope flattened to 0.74 +/- 0.05. The WT spectrum can be fitted by a steep absorbed power-law, with Gamma = 3.00 +0.27/-0.24 and NH = (6.6 +/- 1.1)e21 cm^-2 at z = 0.5295 (Berger, Fox & Cenko, GCN Circ. 8335), in addition to the Galactic value (at z=0) of 1.4e20 cm^-2. The observed (unabsorbed) flux over this time (105-176 s after the trigger) is 3.21e-10 (1.01e-9) erg cm^-2 s^-1. If the decay continues at a slope of 0.74, the predicted count rate at 24 hours after the burst is 0.019 count s^-1, corresponding to an observed (unabsorbed) flux of 7.6e-13 (1.2e-12) erg cm^-2 s^-1. The results of the automatic analysis of the XRT data are available at http://www.swift.ac.uk/xrt_products This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8337 SUBJECT: GRB 081007: Early RAPTOR measurements of optical counterpart DATE: 08/10/07 19:56:45 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis, B. Norman of Los Alamos National Laboratory report: The RAPTOR telescope system responded to Swift trigger 330856 (Baumgartner et al., GCN 8330) under fair observing conditions. Our narrow-field instruments began observing the location at 05:24:17.13 UTC, 24.4 s after the Swift trigger and during the end of the Gamma-Ray emitting interval. We detect the optical counterpart reported by Baumgartner et al. (GCN 8330) and Covino et al. (GCN 8331). We first detect the counterpart at R~16.4 at approximately 90s after the Swift trigger time. The counterpart brightens over the next 50 seconds to magnitude R~15.4 and then begins fading steadily. Our unfiltered images were calibrated against the USNO-B1 R-band. The following table gives selected observations, not corrected for extinction, from this event. t-mid(s) exp(s) mag mag-err -------------------------------------------- 90.31 5.0 16.43 0.22 139.58 10.0 15.38 0.06 367.83 30.0 16.75 0.20 685.42 30.0 17.28 0.19 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8338 SUBJECT: GRB 081007, Swift-BAT refined analysis DATE: 08/10/07 20:01:57 GMT FROM: Wayne Baumgartner at GSFC GRB 081007, Swift-BAT refined analysis C. M. Markwardt (UMD/GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), K. McLean (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081007 (trigger #330856) (Baumgartner et al., GCN Circ. 8330). The BAT ground-calculated position is RA, Dec = 339.963, -40.146 deg which is RA(J2000) = 22h 39m 51.1s Dec(J2000) = -40d 08' 44.8" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%. The mask-weighted light curve shows a large peak of approximately 9 seconds duration at T+0. This peak is seen mostly below 50 keV; a cutoff-powerlaw model fit yields an Epeak of approximately 12 keV. T90 (15-350 keV) is 10.0 +- 4.5 sec (estimated error including systematics). The time-averaged spectrum from T-6.9 to T+7.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.51 +- 0.20. The fluence in the 15-150 keV band is 7.1 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.10 sec in the 15-150 keV band is 2.6 +- 0.4 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/330856/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 1.43. This fluence ratio is larger than 1.32 which can be achieved with a 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: 8338 SUBJECT: GRB 081007, Swift-BAT refined analysis DATE: 08/10/07 20:01:57 GMT FROM: Wayne Baumgartner at GSFC GRB 081007, Swift-BAT refined analysis C. M. Markwardt (UMD/GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), K. McLean (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081007 (trigger #330856) (Baumgartner et al., GCN Circ. 8330). The BAT ground-calculated position is RA, Dec = 339.963, -40.146 deg which is RA(J2000) = 22h 39m 51.1s Dec(J2000) = -40d 08' 44.8" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%. The mask-weighted light curve shows a large peak of approximately 9 seconds duration at T+0. This peak is seen mostly below 50 keV; a cutoff-powerlaw model fit yields an Epeak of approximately 12 keV. T90 (15-350 keV) is 10.0 +- 4.5 sec (estimated error including systematics). The time-averaged spectrum from T-6.9 to T+7.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.51 +- 0.20. The fluence in the 15-150 keV band is 7.1 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.10 sec in the 15-150 keV band is 2.6 +- 0.4 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/330856/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 1.43. This fluence ratio is larger than 1.32 which can be achieved with a 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: 8338 SUBJECT: GRB 081007, Swift-BAT refined analysis DATE: 08/10/07 20:01:57 GMT FROM: Wayne Baumgartner at GSFC GRB 081007, Swift-BAT refined analysis C. M. Markwardt (UMD/GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), K. McLean (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081007 (trigger #330856) (Baumgartner et al., GCN Circ. 8330). The BAT ground-calculated position is RA, Dec = 339.963, -40.146 deg which is RA(J2000) = 22h 39m 51.1s Dec(J2000) = -40d 08' 44.8" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%. The mask-weighted light curve shows a large peak of approximately 9 seconds duration at T+0. This peak is seen mostly below 50 keV; a cutoff-powerlaw model fit yields an Epeak of approximately 12 keV. T90 (15-350 keV) is 10.0 +- 4.5 sec (estimated error including systematics). The time-averaged spectrum from T-6.9 to T+7.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.51 +- 0.20. The fluence in the 15-150 keV band is 7.1 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.10 sec in the 15-150 keV band is 2.6 +- 0.4 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/330856/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 1.43. This fluence ratio is larger than 1.32 which can be achieved with a 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: 8339 SUBJECT: GRB 081007, SMARTS optical afterglow observations DATE: 08/10/08 01:49:15 GMT FROM: Bethany Cobb at Yale U B. E. Cobb (UC Berkeley) reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we continued to obtain optical/IR imaging of the error region of GRB 081007 (GCN 8330, Baumgartner et al.) following GCN 8332. At a mid-exposure time of 2008-10-07 06:04 UT (40 minutes post-burst), the GRB afterglow (GCN 8330, Baumgartner et al.) had the following magnitudes: B = 19.36 +/- 0.04 R = 18.37 +/- 0.03 I = 17.73 +/- 0.03 Observations were obtained under non-photometric conditions. These preliminary magnitudes are calibrated against several USNO-B1.0 stars in the field, so there is likely an additional photometric calibration error of ~0.2 magnitudes. From 23 minutes to 112 minutes post-burst the decay rate of the afterglow remains at alpha = -0.6 (where afterglow flux is proportional to t^alpha) in all our optical colors. Further observations of this burst are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8340 SUBJECT: GRB081007: Swift/UVOT Observations DATE: 08/10/08 12:40:42 GMT FROM: Peter Brown at PSU P. J. Brown (PSU) and W. H. Baumgartner (GSFC/UMGC) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 081007 starting about 109 s after the BAT detection (Baumgartner et al., GCN Circ. 8330). We report additional detections and 3 sigma upper limits of the fading afterglow (where T_start and T_stop represent the elapsed time since the BAT trigger in seconds). Filter T_start(s) T_stop Exp(s) Mag or 3 Sigma Limit uvw2 725 1508 40 >18.8 uvm2 621 1394 59 >18.8 uvw1 646 1419 59 >19.3 u 670 1443 59 18.5 +/- 0.2 b 695 1468 39 19.1 +/- 0.2 v 215 615 394 17.5 +/- 0.1 v 969 1369 393 18.6 +/- 0.1 white 109 209 98 17.0 +/- 0.1 white 862 962 98 18.8 +/- 0.1 The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E(B-V) = 0.015 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). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8352 SUBJECT: GRB 081007: Rapid PROMPT Detections DATE: 08/10/10 02:57:35 GMT FROM: James Philip West at UNC.Chapel Hill J. P. West, M. Schubel, J. Haislip, R. Holmes, D. Reichart, M. Nysewander, A. LaCluyze, K. Ivarsen, J. A. Crain, A. Foster, T. Brennan, R. Rhine, J. Styblova, A. Trotter, and E. Weaver report: Skynet observed the localization of GRB 081007 (Baumgartner et al., GCN 8330) with four of the 16" PROMPT telescopes at CTIO beginning 41 seconds after the trigger (24 seconds after notification) in UBVRI. We detect the afterglow (Baumgartner et al., GCN 8330) in BVRI. At 121 seconds after the burst, we measure I ~ 14.8 mag (calibrated to 6 USNO B1 stars). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8354 SUBJECT: GRB 081007: Radio Detection DATE: 08/10/10 14:09:18 GMT FROM: Alicia Soderberg at Caltech Alicia Soderberg (Harvard/SAO) and Dale Frail (NRAO) report on behalf of a larger collaboration: "We observed the field of GRB 081007 (GCN 8330) with the Very Large Array beginning at Oct 9.19 UT. At 8.46 GHz we detect a radio source coincident with the optical afterglow position at coordinates (J2000): RA = 22 39 50.3882 +/- 0.0009 Dec = -40 08 49.18 +/- 0.03 with flux density 0.32 +- 0.03 mJy. Further observations are scheduled. 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: 8369 SUBJECT: GRB 081007 and GRB 081007B: Fermi GBM detection DATE: 08/10/13 18:18:15 GMT FROM: Elisabetta Bissaldi at MPE E. Bissaldi, S. McBreen (MPE) and V. Connaughton (UAH) report on behalf of the Fermi GBM Team: "At 05:21:51 UT on 7 October 2008, the Fermi Gamma-ray Burst Monitor triggered on a very weak burst GRB 081007B (trigger 245049712/081007224). The duration of this event is about 0.5 s but due to the lack of counts it was not possible to accurately localize it or perform spectral analysis. 121 seconds later, at 05:23:52 UT, Swift/BAT triggered on GRB 081007 (Baumgartner et al., GCN 8330). This event was also detected by GBM. The angle from the Fermi LAT boresight to the Swift position is 116 degrees. Based on the detector geometry GRB081007 does not appear to be related to GRB 081007B. GRB 081007 is single peaked with an estimated T90 (25-900 keV) of about 12 s. The time-averaged spectrum from T0+0.6 s to T0+6.8 s relative to the Swift trigger is adequately fit by a power law with an index of -2.1 +/- 0.1, in agreement with the Swift-BAT refined analysis (Markwardt et al., GCN 8338). It can also be fit with a power law function with an exponential high energy cutoff. The cutoff energy, parameterized as Epeak, is 40 +/- 10 keV. In this case the power law index is poorly constrained (-1.4 +/- 0.4). The fluence (25-900 keV) for the power law model is (1.2 +/- 0.1)E-06 erg/cm2. The 1 sec peak photon flux measured starting from T0+0.9 in the 25-900 keV band is 2.2 +/- 0.2 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: 8662 SUBJECT: GRB 081007: Detection of a Supernova DATE: 08/12/12 16:46:46 GMT FROM: Edo Berger at Harvard Alicia Soderberg, Edo Berger (Harvard CfA), and Derek Fox (PSU) report on behalf of a larger collaboration: "We imaged the optical counterpart of GRB 081007 (Baumgartner et al., GCN 8330) with Gemini-S/GMOS in the griz filters on three separate epochs: Oct 24.02, Nov 2.01, and Dec 5.04 UT corresponding to 16.80, 25.79, and 58.82 days after the burst, respectively. Using the ISIS image subtraction package and adopting our third epoch as a template image, we find a residual source in the first and second epochs at a position coincident with that of the early afterglow. A comparison of the residual flux indicates that the transient increased by roughly 0.4 mag in i-band between the first and second epochs and then subsequently faded. We attribute this photometric evolution to a supernova component, in line with the recent report of spectroscopic evidence for an underlying Type Ibc supernova (Della Valle et al., CBET 1602). Accounting for a redshift of z=0.53 (Berger et al., GCN 8335), the k-corrected absolute magnitude of the object in our second epoch i-band image is fainter than that SN 1998bw at the same (rest-frame) time. Further analysis is on-going." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8951 SUBJECT: Radio observation of GRB 081007 with ATCA DATE: 09/03/09 05:43:46 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 SWIFT-UVOT position of the GRB081007 afterglow (GCN 8330) at 4.800 and 4.928 GHz with the Australia Telescope Compact Array (ATCA) between 01:00:00 UT and 22:00:00 UT on February 21/22, 2009. We did not detect a radio source at the position of the GRB081007 afterglow (GCN 8330). The data at 4.800 and 4.928 GHz were merged and the radio flux density at the GRB optical afterglow position found out to be -0.215 +/- 0.006 mJy/beam (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 the 4.800 & 4.928 GHz combined image at: http://cira.ivec.org/dokuwiki/doku.php/grb/grb081007/grb081007_field_image