TITLE: GCN CIRCULAR NUMBER: 7281 SUBJECT: GRB 080210: Swift detection of a burst with optical afterglow DATE: 08/02/10 08:27:08 GMT FROM: David Palmer at LANL D. Grupe (PSU), W. H. Baumgartner (GSFC/UMBC), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), E. A. Hoversten (PSU), C. B. Markwardt (CRESST/GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Stamatikos (NASA/ORAU) and M. C. Stroh (PSU) report on behalf of the Swift Team: At 07:50:05 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080210 (trigger=302888). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 251.270, +13.830 which is RA(J2000) = 16h 45m 05s Dec(J2000) = +13d 49' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peak with substructure with a duration of about 35 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~10 sec after the trigger. This was an image trigger, but with a clear light curve. The XRT began observing the field at 07:54:08 UT, 243 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 251.2679, +13.8254 which is RA(J2000) = 16h 45m 04.3s Dec(J2000) = 13d 49' 31.4" with an uncertainty of 4.6 arcseconds (radius, 90% containment). This location is 18.1 arcseconds from the BAT on-board position, within the BAT error circle. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 160 seconds after the BAT trigger, and an exposure of 193 seconds with the v filter starting 266 seconds after the trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA, Dec = 251.2667, +13.8267 (white) which is RA(J2000) = 16:45:04.01 DEC(J2000) = +13:49:36.1 with a 1-sigma error radius of about 0.6 arc sec. This position is 6.3 arcseconds from the center of the XRT error circle. The estimated magnitude is 18.0 in white and 17.6 in v with 1-sigma errors of about 0.5 mag. The positions agree in both white and v. No correction has been made for the expected extinction corresponding to E(B-V) of 0.08. Burst Advocate for this burst is D. Grupe (grupe 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.)