TITLE: GCN CIRCULAR NUMBER: 30447 SUBJECT: GRB 210712A: Swift detection of a burst DATE: 21/07/12 09:58:21 GMT FROM: Hans Krimm at NSF/NASA-GSFC B. Sbarufatti (PSU), H. A. Krimm (NSF) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 09:43:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210712A (trigger=1059881). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 97.337, -35.393 which is RA(J2000) = 06h 29m 21s Dec(J2000) = -35d 23' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 20 sec, followed by lower-level extended emission. The peak count rate was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 09:44:32.5 UT, 80.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 97.3319, -35.3717 which is equivalent to: RA(J2000) = 06h 29m 19.66s Dec(J2000) = -35d 22' 18.0" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://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 in excess of the Galactic value (8.88 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.5 (+5.28/-4.30) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 3.52e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 90 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 0.076. Burst Advocate for this burst is B. Sbarufatti (bxs60 AT 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/)