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GCN Circular 8648

GRB 081210: Swift detection of a burst with optical afterglow
2008-12-10T20:37:36Z (16 years ago)
David Palmer at LANL <>
H. A. Krimm (CRESST/GSFC/USRA), A. P. Beardmore (U Leicester),
P. J. Brown (PSU), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), C. Guidorzi (UniFE),
S. T. Holland (CRESST/USRA/GSFC), S. D. Hunsberger (PSU),
S. Immler (CRESST/GSFC/UMD), J. A. Kennea (PSU), W.B Landsman (GSFC),
F. E. Marshall (NASA/GSFC), J. P. Osborne (U Leicester),
C. Pagani (PSU), D. M. Palmer (LANL), A. M. Parsons (GSFC),
M. Stamatikos (NASA/ORAU) and E. Troja (INAF-IASFPA) report on behalf
of the Swift Team:

At 20:19:34 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 081210 (trigger=337073).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 70.458, -11.266 which is 
   RA(J2000) = 04h 41m 50s
   Dec(J2000) = -11d 15' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 30 sec, followed by an additional
peak at T+140 s.  The peak count rate was ~5000 counts/sec 
(15-350 keV), at ~18 sec after the trigger. 

The XRT began observing the field at 20:20:46.1 UT, 71.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 70.4853, -11.2568 which is equivalent to:
   RA(J2000)  = 04h 41m 56.47s
   Dec(J2000) = -11d 15' 24.4"
with an uncertainty of 5.4 arcseconds (radius, 90% containment). This
location is 101 arcseconds from the BAT onboard position, within the
BAT error circle. The full field-of-view light curve shows a strong flare
at T+140 s, coincident with a flare seen in the BAT. No event data are yet
available to determine the column density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 1.35e-09 erg cm^-2 s^-1 (0.2-10

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 80 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	04:41:56.20 = 70.48417
  DEC(J2000) = -11:15:26.7  = -11.25741
with a 90%-confidence error radius of about 0.64 arc sec. This position is 4.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.12 with a 1-sigma error of about 0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.08.  The afterglow is detected
in the UVOT u filter, so the redshift must be less than approximately 3.3. 

Burst Advocate for this burst is H. A. Krimm (krimm 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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