TITLE: GCN CIRCULAR NUMBER: 8180 SUBJECT: GRB 080905: Swift detection of a probably-short burst DATE: 08/09/05 12:19:45 GMT FROM: Claudio Pagani at PSU/Swift-XRT C. Pagani (PSU), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), D. Grupe (PSU), 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), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Preger (ASDC), J. L. Racusin (PSU), P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-IASFPA), P. Schady (MSSL-UCL), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), M. C. Stroh (PSU), E. Troja (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 11:58:54 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080905 (trigger=323870). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 287.662, -18.877 which is RA(J2000) = 19h 10m 39s Dec(J2000) = -18d 52' 37" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows 3 peaks with a total duration of about 2 sec. The spectrum is hard, with most response above 25 keV in the BAT energy range. The peak count rate was ~4500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 12:01:05.3 UT, 130.4 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 287.67363, -18.87986 which is equivalent to: RA(J2000) = 19h 10m 41.67s Dec(J2000) = -18d 52' 47.5" with an uncertainty of 2.8 arcseconds (radius, 90% containment). This location is 40 arcseconds from the BAT onboard position, within the BAT error circle. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 8.95e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 114 seconds after the BAT trigger. No 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 3-sigma upper limit at the location of the XRT position is 17.8 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.14. Burst Advocate for this burst is C. Pagani (pagani AT astro.psu.edu). 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.)