TITLE: GCN CIRCULAR NUMBER: 32191 SUBJECT: GRB 220611A: Swift detection of a burst DATE: 22/06/11 18:36:01 GMT FROM: David Palmer at LANL S. B. Cenko (GSFC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC), V. D'Elia (SSDC & INAF-OAR), J.D. Gropp (PSU), J. A. Kennea (PSU), S. Laha (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 18:01:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220611A (trigger=1110090). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 66.526d, -37.289d which is RA(J2000) = 04h 26m 06s Dec(J2000) = -37d 17' 20 with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to a telemetry gap, the BAT onboard lightcurve is not immediately available. However, the triggering algorithm found the source in an 8 second image, indicating a long GRB. The XRT began observing the field at 18:04:20.4 UT, 149.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 66.51418, -37.25899 which is equivalent to: RA(J2000) = 04h 26m 03.40s Dec(J2000) = -37d 15' 32.4" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 113 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 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 consistent with the Galactic value of 2.66 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 152 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 0.033. We note that this source location is ~15 arcsec from the line of sight to the galaxy MCG-06-10-007, which is described in Simbad as an S0 galaxy, B=16.3, z~0.049, angular size 18"x16". Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 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/)