//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8753 SUBJECT: GRB 081230: Swift detection of a burst DATE: 08/12/30 21:02:09 GMT FROM: Scott Barthelmy at NASA/GSFC V. La Parola (INAF-IASFPA), S. D. Barthelmy (GSFC), P. J. Brown (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), W.B Landsman (GSFC), V. Mangano (INAF-IASFPA), J. P. Osborne (U Leicester), K. L. Page (U Leicester), B. Sbarufatti (INAF-IASFPA) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 20:36:12 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081230 (trigger=338633). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 37.315, -25.142 which is RA(J2000) = 02h 29m 16s Dec(J2000) = -25d 08' 29" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 50 sec. The peak count rate was ~600 counts/sec (15-350 keV), at ~50 sec after the trigger. The XRT began observing the field at 20:38:16.7 UT, 124.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 37.33148, -25.14645 which is equivalent to: RA(J2000) = 02h 29m 19.56s Dec(J2000) = -25d 08' 47.2" with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 56 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 in excess of the Galactic value (1.68e+20 cm^-2, Kalberla et al. 2005), with an excess column of 3.2 (+2.81/-2.34) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 132 seconds after the BAT trigger. No credible 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 typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. Burst Advocate for this burst is V. La Parola (laparola AT ifc.inaf.it). 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: 8754 SUBJECT: GRB 081230: ROTSE-III Detection of Optical Counterpart DATE: 08/12/30 21:20:41 GMT FROM: Fang Yuan at ROTSE F. Yuan (U Mich), E.S. Rykoff (UCSB), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 081230 (Swift trigger 338633). The first image was at 20:47:53.4 UT, 700.8 s after the burst (8.4 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 19.1 magnitude, steady source in the XRT error box with coordinates: 02:29:19.35 -25:08:49.22 (J2000), with positional uncertainty of 1" or better start UT mag mlim(of image) ---------------------------------- 20:49:23.0 19.1 19.2 This source is not visible in DSS (second epoch), 2MASS or the MPChecker database. A jpeg image is available at http://www.rotse.net/images/gsb338633_3c021-030_key.jpg Continuing observations are in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8755 SUBJECT: GRB 081230: Swift/UVOT Detection of an Optical Afterglow DATE: 08/12/30 21:21:51 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA), P. J. Brown (PSU), and V. La Parola (INAF-IASFPA) report on the behalf of the Swift UVOT team: The Swift/UVOT detects a faint source in the XRT error circle for GRB 081230 (La Parola, et al. 2008, GCN Circ. 8753). The source has a preliminary position of RA (J2000) 02:29:19.48 = 37.33117 (deg) Dec (J2000) -25:08:48.5 = -25.14682 (deg) and a preliminary u-band magnitude of u = 20.6 +/- 0.3 mag in a 250 s exposure starting 131 s after the BAT trigger. The quoted magnitude has not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.01 mag (Schlegel, et al., 1998, ApJS, 500, 525). The photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8756 SUBJECT: GRB 081230: Enhanced Swift-XRT position DATE: 08/12/31 01:11:24 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1640 s of XRT Photon Counting mode data and 4 UVOT images for GRB 081230, 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 = 37.3314, -25.1477 which is equivalent to: RA (J2000): 02h 29m 19.53s Dec (J2000): -25d 08' 51.8" 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: 8757 SUBJECT: GRB 081230 Swift/UVOT Observations DATE: 08/12/31 12:31:41 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) and V. La Parola (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began observerving the field of GRB 081230 132 s after the BAT trigger ( La Parola et al., GCN Circ. 8753). We detect the optical afterglow in the white, v, b and u filters at the position: RA(J2000.0) = 02:29:19.467 DEC(J2000.0) = -25:08:51.0 with an estimated uncertainty of 0.9 arcsec (radius, 90% confidence). This position is consistent with the UVOT-enhanced XRT position (Osborne et al., GCN 8756) and the optical afterglow position reported by ROTSE-III (Yuan et al., GCN 8754). The magnitudes and 3 sigma upper limits are reported below: Filter T_start (s) T_stop Exposure Mag/3sig UL ------------------------------------------------------------ white 4060 4210 147 20.45 +/- 0.35 v 587 607 19 18.30 +/- 0.48 b 388 408 19 18.92 +/- 0.36 u 132 382 246 20.28 +/- 0.38 u 511 531 19 19.04 +/- 0.52 uvw1 487 5854 435 > 21.23 uvm2 462 5649 255 > 20.95 uvw2 414 6575 353 > 21.44 ------------------------------------------------------------ The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.01 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383,627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8758 SUBJECT: GRB081230: Swift-XRT refined analysis DATE: 08/12/31 14:23:44 GMT FROM: Valentina La Parola at INAF-IASPA V. La Parola, B. Sbarufatti, V. Mangano (INAF-IASF Pa) report on behalf of the Swift XRT team: We have analysed the first 35 ks of XRT observations for GRB 081230 (La Parola et al. GCN Circ 8753), with an exposure time of 104 s in WT mode and 11.4 ks in PC mode. The astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 37.3314 -25.1477, corresponding to: RA (J2000): 02h 29m 19.53s Dec (J2000): -25d 08' 51.8 with an uncertainty of 1.8 arcsec (radius, 90% confidence, Osborne et al. GCN Circ 8756). The lightcurve can be fitted with a broken power-law with the following parameters: alpha1=-6.910+/-0.007 T_break=298+/-9 alpha2=-0.62+/-0.5 There is evidence for a late flare a peaking at 5000s. The spectrum of the data collected in WT mode can be fitted with a powerlaw with photon index Gamma = 1.96 +/- 0.11, absorbed by the Galactic column in this direction of 1.7x10^20 cm^-2, plus an intrinsic column of (6.4+/-2.2)x10^20 cm^-2. The observed (unabsorbed) flux over this time is 1.03x10^-9 (1.3x10^-9) erg cm^-2 s^-1, corresponding to a counts to observed flux conversion of 4.1x10^-11 erg cm^-2 count^-1. The spectrum of the data collected in PC mode can be fitted with a powerlaw with photon index Gamma = 2.14 (+0.10,-0.20), with an intrinsic column of (5.3 [+2.2,-3.7])x10^20 cm^-2. The observed (unabsorbed) flux over this time is 2.1x10^-12 (2.7x10^-9) erg cm^-2 s^-1, With the present decay law, the count rate at 24 hours is predicted to be 1.1x10^-2 c/s (corresponding to an observed flux of 3.7x10^-13 erg cm^-2 s^-1) This circular is an official product of the Swift-XRT team. I.A.S.F. INAF Mailing System Outgoing mail is certified Virus Free. Checked by McAfee anti-virus system //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8759 SUBJECT: GRB 081230, Swift-BAT refined analysis DATE: 08/12/31 15:07:48 GMT FROM: Hans Krimm at NASA-GSFC D. M. Palmer (LANL), 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), V. La Parola (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), 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-300 to T+1197 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081230 (trigger #338633) (La Parola, et al., GCN Circ. 8753). The BAT ground-calculated position is RA, Dec = 37.330, -25.145 deg which is RA(J2000) = 02h 29m 19.2s Dec(J2000) = -25d 08' 42.6" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve consists of a series of overlapping peaks ranging from T+5 sec to T+70 sec, with the strongest emission at ~T+50 seconds. T90 (15-350 keV) is 60.7 +- 13.8 sec (estimated error including systematics). The time-averaged spectrum from T-14.4 to T+62.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.97 +- 0.16. The fluence in the 15-150 keV band is 8.2 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+46.63 sec in the 15-150 keV band is 0.7 +- 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/338633/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8760 SUBJECT: GRB 081230: GROND confirmation of the afterglow DATE: 09/01/01 15:20:21 GMT FROM: Paulo M. J. Afonso at MPE GRB 081230: GROND confirmation of the afterglow P. Afonso (MPE), C. Clemens (MPE), S. Klose (Tautenburg), J. Greiner (MPE) and G. Szokoly (Eotvos 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) imaged the field of GRB 081230 (Swift trigger 338633, La Parola et al., GCN #8753) simultaneously in g'r'i'z'JHK bands We detected and confirm the afterglow candidate in all bands, at the position: RA(J2000): 02:29:19.51 DEC(J2000): -25:08:49.95 with uncertainties of 0.5" in each coordinate. This position is compatible with UVOT (Oates et alia, GCN #8757) and ROTSE-III (Yuan et alia, GCN #8754) reported positions. Observations started on Dec. 31 at 00h48 UT, 15123 seconds, or ~ 4.2 hours after the burst. We used 4 images of 375 s exposure in g'r'i'z' and 120 images of 10s exposure in JHK, for each epoch. The images mid time for the 1st epoch is 5.99h (or 21564 seconds) after the burst. Observations were done at an average air mass = 1.128 and seeing ~ 1.5''. We took a 2nd epoch on January 1st, 2009, starting at 03h21 UT. The images mid time for the 2nd epoch is 30.99h (or 111564 seconds) after the burst. Observations were done at an average air mass = 1.334 and seeing ~ 1.3''. The preliminary data for the 2nd epoch clearly confirms the fading of the afterglow: We present preliminary photometric results for g'r'i'z'. The AB magnitudes, using GROND zero points are as follows: 1st epoch 2nd epoch g' = 21.32 +- 0.02 23.67 +- 0.08 r' = 20.96 +- 0.01 23.07 +- 0.06 i' = 20.74 +- 0.02 22.79 +- 0.09 z' = 20.66 +- 0.03 22.84 +- 0.17 No correction for galactic extinction was done. The quoted error is statistical only. There is an additional systematic error in the absolute calibration using the GROND zeropoints which is expected to be in the 0.2 mag range. Further data analysis is ongoing for JHK - the aftegrlow being clearly visible on the first epoch, but not on the 2nd.