TITLE: GCN CIRCULAR NUMBER: 14331 SUBJECT: GRB 130327A: Swift detection of a burst DATE: 13/03/27 02:09:19 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT T. N. Ukwatta (MSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), M. H. Siegel (PSU) and C. A. Swenson (PSU) report on behalf of the Swift Team: At 01:47:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130327A (trigger=552063). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 91.992, +55.730 which is RA(J2000) = 06h 07m 58s Dec(J2000) = +55d 43' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a weak single peak with a duration of about 10 sec. The peak count rate was ~900 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 01:49:55.0 UT, 141.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 92.0387, 55.7143 which is equivalent to: RA(J2000) = 06h 08m 09.29s Dec(J2000) = +55d 42' 51.5" with an uncertainty of 2.7 arcseconds (radius, 90% containment). This location is 110 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.31 x 10^21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 104 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.13. Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 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.)