GCN Circular 11957

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.)