//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8729 SUBJECT: GRB 081226: Swift detection of a possible short-hard burst DATE: 08/12/26 01:21:22 GMT FROM: David Burrows at PSU/Swift O. Godet (U Leicester), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), E. A. Hoversten (PSU), J. A. Kennea (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 01:03:37 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081226 (trigger=338177). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 120.527, -69.006 which is RA(J2000) = 08h 02m 06s Dec(J2000) = -69d 00' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a short hard burst structure with a duration of about 0.5 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 01:05:11.9 UT, 94.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 120.50054, -69.02994 which is equivalent to: RA(J2000) = 08h 02m 0.13s Dec(J2000) = -69d 01' 47.8" with an uncertainty of 4.5 arcseconds (radius, 90% containment). This location is 92 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 1.19e+21 cm^-2 (Kalberla et al. 2005). The UVOT data has not yet been received so it is not possible to comment on the UV/optical nature of the burst at this time. There is a 7th magnitude source nearby which will complicate UVOT observations. Burst Advocate for this burst is O. Godet (og19 AT star.le.ac.uk). 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: 8730 SUBJECT: GRB 081226: ROTSE-III Optical Limits DATE: 08/12/26 01:32:34 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), E.S. Rykoff (UCSB), F. Yuan (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 081226 (Swift trigger 338177; Godet, GCN 8729), producing images beginning 8.8 s after the GCN notice time. An automated response took the first image at 01:04:02.8 UT, 25.4 s after the burst, under excellent conditions. We took 10 5-sec, 20 20-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; the field is not crowded. Individual images have limiting magnitudes ranging from 16.8-17.4; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 01:04:02.8 01:04:07.8 5 17.0 25.4 N 01:04:02.9 01:05:19.0 76 17.8 25.5 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8731 SUBJECT: GRB 081226: GROND afterglow candidate DATE: 08/12/26 03:08:29 GMT FROM: Paulo M. J. Afonso at MPE GRB 081226: GROND afterglow candidate P. Afonso, T. Kruehler (both MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching) 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),started observations of the field of GRB 081226 (Godet et al. 2008, GCN #8729) in g'r'i'z'JHK at 01:14 UTC, 11 min after the burst. We detect a faint optical source in the XRT error circle (Godet et al. 2008, GCN #8729) at: RA(J2000): 08:01:59.92 DEC(J2000): -69:01:47.4 with uncertainties of 0.5". At a midtime of 01:57 UTC, we measure a rough preliminary r' band magnitude of 24.3 calibrated with the GROND zeropoint. No statement about variability can be made at this point. Observations are ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8732 SUBJECT: GRB 081226: Gemini-South imaging DATE: 08/12/26 03:26:41 GMT FROM: Edo Berger at Harvard E. Berger (Harvard), A. Cucchiara, and D. B. Fox (Penn State) report: "We imaged the error circle of GRB 081226 (GCN 8729) with GMOS on the Gemini-S telescope starting on 2008 Dec 26.04 UT. In a single 300 sec r-band image we detect the object located by GROND within the XRT error circle (GCN 8731). In addition, we find a second, fainter source within the error circle at (J2000): RA = 08:02:00.44 DEC = -69:01:48.9 with an uncertainty of about 0.5" in each coordinate. Additional observations are on-going to determine if either of these two sources is fading." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8733 SUBJECT: GRB 081226: Gemini-South spectrum of possible afterglow DATE: 08/12/26 04:51:20 GMT FROM: Edo Berger at Harvard E. Berger (Harvard), A. Cucchiara, and D. B. Fox (Penn State) report: "We obtained spectroscopic observations of the possible afterglow of GRB 081226 (GCNs 8731, 8732) with GMOS on the Gemini-South telescope using the R400 grating with a central wavelength of 6000A for a total of 2400 sec. We detect smooth continuum emission but no obvious absorption or emission features in the wavelength range 4000-8000A. Further analysis is on-going." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8736 SUBJECT: GRB 081226: Second epoch of Gemini-South imaging DATE: 08/12/26 16:27:15 GMT FROM: Edo Berger at Harvard E. Berger, A. M. Soderberg (Harvard), A. Cucchiara, and D. B. Fox (Penn State) report: "We re-observed the error circle of GRB 081226 (GCN 8729) with GMOS on the Gemini-South telescope on 2008 Dec 26.349 UT (7.31 hours post burst). A comparison to our first epoch of imaging, taken on 2008 Dec 26.112 UT (1.62 hours post burst; GCN 8732), reveals that neither of the two objects within the XRT error circle (GCN 8732) have varied in brightness. This is confirmed using digital image subtraction with the ISIS package." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8738 SUBJECT: GRB 081226: Swift-XRT refined analysis DATE: 08/12/26 22:40:57 GMT FROM: Olivier Godet at U.of Leicester O. Godet (U Leicester) on behalf the Swift-XRT team: The Swift-XRT started observing the field of GRB 081226 (trigger number 338177, Godet et al., GCN Circ. 8729) at 2008-12-26 01:05:11.9 UT, 94.5 seconds after the trigger. Using 11.6 ks of photon counting (PC) mode data, the best XRT position is located at RA, Dec 120.50152, -69.02924 which is equivalent to: RA(J2000) = 08h 02m 00.36s Dec(J2000) = -46d 01' 45.2" with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 2.8 arcseconds from the XRT position given in Godet et al. (GCN Circ. 8729). It is also consistent with the position of the possible optical counterpart reported by Afonso et al. (GCN Circ. 8731). The X-ray light curve presently spans 11.6 ks of PC mode data from T+109 s to T+42 ks. Due to poor statistics, it is difficult to properly model the light-curve, which shows a decay (with a slope around 1.8) possibly followed by a flattening at later time. The PC X-ray spectrum from the same interval can be well fit by an absorbed power-law with a photon index of 2.60 +1.61/-0.98 and a column density of (6.4 +8.8/-4.6) x 10^21 cm^-2 (the Galactic value is 1.19 x 10^21 cm^-2 in the direction of the burst - Kalberla et al. 2005). The observed 0.4-10.0 keV flux is (1.8 +0.8/-1.3) x 10^-13 erg cm^-2 s^-1 which corresponds to an unabsorbed flux of (4.7 +1.4/-2.5) x 10^-13 erg cm^-2 s^-1. No more Swift observations are planned for this burst. This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8952 SUBJECT: Radio observation of GRB 081226a with ATCA DATE: 09/03/09 06:03:08 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 GROND position of the GRB081226a afterglow (GCN 8731) 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 GRB081226a (GCN 8731). 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 0.115 +/- 0.180 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/grb081226a/grb081226a_field_image //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8953 SUBJECT: Radio observation of GRB 081226b with ATCA DATE: 09/03/09 06:10:48 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 INTEGRAL-IBAS position of the GRB081226b (GCN 8734) 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 GRB081226b (GCN 8734). The data at 4.800 and 4.928 GHz were merged and the radio flux density at the GRB position found out to be -0.176 +/- 0.196 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/grb081226b/grb081226b_field_image