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GCN Circular 12810

Subject
GRB 120106A: Swift detection of a burst
Date
2012-01-06T14:26:13Z (12 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
S. Immler (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC),
H. A. Krimm (CRESST/GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU),
O. M. Littlejohns (U Leicester), F. E. Marshall (NASA/GSFC),
C. J. Mountford (U Leicester), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC),
C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), R. L. C. Starling (U Leicester),
T. N. Ukwatta (MSU) and B.-B. Zhang (PSU) report on behalf of the
Swift Team:

At 14:16:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120106A (trigger=511235).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 66.129, +64.028, which is 
   RA(J2000)  =  04h 24m 31s
   Dec(J2000) = +64d 01' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve show several overlapping peaks
starting ~T-8 sec with a total duration of about 20 sec.  The peak count rate
was ~2400 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 14:17:39.0 UT, 74.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 66.11105, 64.03810 which
is equivalent to:
   RA(J2000)  = 04h 24m 26.65s
   Dec(J2000) = +64d 02' 17.2"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 46 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 http://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 (2.65 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 4.8
(+4.97/-3.87) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.88e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 84 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. 
Data from the list of sources generated on-board are not available at this
time. No correction has been made for the expected extinction corresponding to
E(B-V) of 1.19. 

Burst Advocate for this burst is S. Immler (stefan.immler 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/too.html.)
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