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GCN Circular 12209

Swift detection of a SGR-like burst from the AXP 4U 0142+61
2011-07-29T11:52:33Z (13 years ago)
David Palmer at LANL <>
S. R. Oates (UCL-MSSL), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), S. Campana (INAF-OAB),
N. Gehrels (NASA/GSFC), E. A. Hoversten (PSU),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),
C. J. Mountford (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), P. Romano (INAF-IASFPA), C. J. Saxton (UCL-MSSL),
B. Sbarufatti (INAF-OAB/IASFPA) and G. Tagliaferri (INAF-OAB) report
on behalf of the Swift Team:

At 11:19:15 UT, the Swift Burst Alert Telescope (BAT) triggered and
located on a short burst from the AXP 4U 0142+61 (trigger=458345).  
Swift slewed immediately to the source location. 
The BAT on-board calculated location is 
RA, Dec 26.598, +61.729 which is 
   RA(J2000) = 01h 46m 24s
   Dec(J2000) = +61d 43' 43"
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 0.1 sec.  The peak count rate
was ~3500 counts/sec (15-350 keV), at ~0.1 sec after the trigger. 

The XRT began observing the field at 11:20:38.1 UT, 82.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright
source with an enhanced position: RA,Dec = 26.5937, 61.7510 (degrees) 
which is equivalent to:

RA  (J2000.0) = 01 46 22.48
DEC (J2000.0) = +61 45 03.6

with an uncertainty of 2.2 arcsec (radius, 90% containment). 
This is consistent with the position of 4U 0142+61. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 93 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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 large, but uncertain extinction expected. 

Swift has been regularly monitoring this source 4U 0142+61 as
part of program of regular monitoring of AXPs (PI: V. Kaspi). 
This AXP has previously been seen to emit SGR-like bursts
(e.g. ATEL #794, Kaspi et al., 2006)

Burst Advocate for this burst is S. R. Oates (sro AT 
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:
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