TITLE: GCN CIRCULAR NUMBER: 7847 SUBJECT: GRB 080607: Swift detection of a burst with optical afterglow DATE: 08/06/07 06:21:44 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano (INAF-IASFPA), J. R. Cummings (NASA/UMBC), G. Cusumano (INAF-IASFPA), N. Gehrels (NASA/GSFC), V. La Parola (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD), J. P. Osborne (U Leicester), B. Sbarufatti (INAF-IASFPA) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 06:07:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080607 (trigger=313417). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 194.967, +15.900 which is RA(J2000) = 12h 59m 52s Dec(J2000) = +15d 54' 01" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peak structure with a duration of about 80 sec. The peak count rate was ~35000 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 06:08:49.1 UT, 82.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 194.9462, +15.9208 which is equivalent to: RA(J2000) = 12h 59m 47.0s Dec(J2000) = +15d 55' 14.8" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 103 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. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 92 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 12:59:47.21 = 194.9467 DEC(J2000) = +15:55:10.9 = 15.9197 with a 1-sigma error radius of about 0.5 arc sec. This position is 4.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.7 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 0.02. Burst Advocate for this burst is V. Mangano (vanessa 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.)