TITLE: GCN CIRCULAR NUMBER: 11957 SUBJECT: GRB 110422A: Swift detection of a burst DATE: 11/04/22 16:04:43 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano (INAF-IASFPA), D. N. Burrows (PSU), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), B. Gendre (ASDC), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU) and C. A. Swenson (PSU) report on behalf of the Swift Team: At 15:41:55 UT, the Swift Burst Alert Telescope (BAT) triggered and located the bright GRB 110422A (trigger=451901). Swift slewed to the burst after a 12 minute observing constraint delay. The BAT on-board calculated location is RA, Dec 111.995, +75.106 which is RA(J2000) = 07h 27m 59s Dec(J2000) = +75d 06' 21" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex peak structure with a duration of about 50 sec. The peak count rate was ~24000 counts/sec (15-350 keV), at ~8 sec after the trigger. The XRT began observing the field at 15:55:30.4 UT, 814.5 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 112.0580, +75.1077 which is equivalent to: RA(J2000) = 07h 28m 13.92s Dec(J2000) = +75d 06' 27.7" with an uncertainty of 6.1 arcseconds (radius, 90% containment). This location is 58 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 150 seconds with the White filter starting 821 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 0.03. 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.)