TITLE: GCN CIRCULAR NUMBER: 7828 SUBJECT: GRB 080605: Swift detection of a burst with an optical afterglow DATE: 08/06/06 00:13:48 GMT FROM: David Palmer at LANL B. Sbarufatti (INAF-IASFPA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), V. La Parola (INAF-IASFPA), V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (NASA/UMBC), T. N. Ukwatta (GSFC/GWU) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 23:47:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080605 (trigger=313299). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 262.127, +4.002 which is RA(J2000) = 17h 28m 31s Dec(J2000) = +04d 00' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple overlapping peaks lasting at least to T+8 sec (at which the TDRSS lightcurve is truncated). The peak count rate was ~17000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 23:49:28.2 UT, 90.4 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 262.1249, +4.0153 which is equivalent to: RA(J2000) = 17h 28m 29.9s Dec(J2000) = +04d 00' 55.0" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 48 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The UVOT detects a new source within the XRT error circle. We are unable to obtain a position or magnitude at this time. The source is very close to a known source in the DSS. Further information will be provided when it is available. Burst Advocate for this burst is B. Sbarufatti (sbarufatti 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.)