GCN Circular 7240

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G. Stratta (ASDC), M. Perri (ASDC) and D. N. Burrows (PSU)
report on behalf of the Swift-XRT team:

The Swift-XRT began observing GRB 080129 (trigger=301981) on
2008-01-29 at 07:00:17 UT, 53 minutes after the BAT trigger
(Immler et al., GCN Circ. 7226
Not found
 
 
).

Using 2045 s of overlapping XRT Photon Counting mode and UVOT
v-band data for GRB 080129, we find a refined astrometrically
corrected X-ray position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec =  105.284125, -7.846722 which is equivalent to:

RA (J2000): 07h 01m 8.19s
Dec (J2000): -07d 50' 48.2"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).
This is 1.2 arcsec away from the previous position derived from the
XRT and UVOT data reported in Goad et al. (GCN Circ. 7230
Not found
 
 
),
51 arcsec from the refined BAT position of Barthelmy et al.
(GCN Circ. 7235
Not found
 
 
) and 1.9 arcsec from the Gemini South position
(GCN Circ. 7229
Not found
 
 
).

The X-ray light curve from T + 3.2 ks to T + 85.8 ks can be
fitted by a broken power law model (chi2 of 39 for 28 degrees
of freedom) with a temporal break at about T + 15.5 ks and
decay indices alpha1 = 0.6 +/- 0.1 and alpha2 = 1.5 +/- 0.1
before and after the break, respectively.

The 0.3-10 keV spectrum from T + 3.2 ks to T + 32.2 ks
is well fit by an absorbed power law
(reduced chi2 of 1.02, with 20 degrees of freedom).
The best fit photon index is 2.0 +/- 0.1, with an hydrogen column
density of (2 +/- 1)e21 cm^-2, in addition to the Galactic column along
the line of sight of 6.3e21 cm^-2 (Kalberla et al. 2005).
The observed (unabsorbed) flux in the 0.3-10 keV band is
4.2e-12 (8.5e-12) erg cm^-2 s^-1.

The timing and spectral behaviors are completely consistent
with those of a typical GRB X-ray afterglow,
removing any uncertainty about the nature of this burst.

The predicted XRT count rate 48 hours after the trigger is 1.6e-3
count s^-1, which corresponds to an observed 0.3-10.0 keV flux of
1.3e-12 ergs cm^-2 s^-1.

This circular is an official product of the Swift-XRT team.

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G. Stratta (ASDC), M. Perri (ASDC) and D. N. Burrows (PSU) <br>report on behalf of the Swift-XRT team:<br>&nbsp;<br>The Swift-XRT began observing GRB 080129 (trigger=301981) on <br>2008-01-29 at 07:00:17 UT, 53 minutes after the BAT trigger&nbsp; <br>
(Immler et al., GCN Circ. 7226
Not found
 
 
). <br><br>Using 2045 s of overlapping XRT Photon Counting mode and UVOT<br>v-band data for GRB 080129, we find a refined astrometrically <br>corrected X-ray position (using the XRT-UVOT alignment and <br>
matching UVOT field sources to the USNO-B1 catalogue): <br>RA, Dec =&nbsp; 105.284125, -7.846722 which is equivalent to:<br><br>RA (J2000): 07h 01m 8.19s<br>Dec (J2000): -07d 50&#39; 48.2&quot;<br><br>with an uncertainty of 2.0 arcsec (radius, 90% confidence).<br>
This is 1.2 arcsec away from the previous position derived from the <br>XRT and UVOT data reported in Goad et al. (GCN Circ. 7230
Not found
 
 
),&nbsp; <br>51 arcsec from the refined BAT position of Barthelmy et al. <br>(GCN Circ. 7235
Not found
 
 
) and 1.9 arcsec from the Gemini South position <br>
(GCN Circ. 7229
Not found
 
 
).<br><br>The X-ray light curve from T + 3.2 ks to T + 85.8 ks can be <br>fitted by a broken power law model (chi2 of 39 for 28 degrees <br>of freedom) with a temporal break at about T + 15.5 ks and <br>decay indices alpha1 = 0.6 +/- 0.1 and alpha2 = 1.5 +/- 0.1 <br>
before and after the break, respectively. <br><br>The 0.3-10 keV spectrum from T + 3.2 ks to T + 32.2 ks <br>is well fit by an absorbed power law <br>(reduced chi2 of 1.02, with 20 degrees of freedom). <br>The best fit photon index is 2.0 +/- 0.1, with an hydrogen column <br>
density of (2 +/- 1)e21 cm^-2, in addition to the Galactic column along <br>the line of sight of 6.3e21 cm^-2 (Kalberla et al. 2005). <br>The observed (unabsorbed) flux in the 0.3-10 keV band is <br>4.2e-12 (8.5e-12) erg cm^-2 s^-1. <br>
<br>The timing and spectral behaviors are completely consistent <br>with those of a typical GRB X-ray afterglow, <br>removing any uncertainty about the nature of this burst.<br><br>The predicted XRT count rate 48 hours after the trigger is 1.6e-3 <br>
count s^-1, which corresponds to an observed 0.3-10.0 keV flux of <br>1.3e-12 ergs cm^-2 s^-1.<br><br>This circular is an official product of the Swift-XRT team.<br><br clear="all"><br><br>

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