[vsnet-grb-info 2844] GRB 060204C: XRT analysis of Swift J061223.0+701243.9

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4681
SUBJECT: GRB 060204C: XRT analysis of Swift J061223.0+701243.9
DATE:    06/02/06 01:48:11 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe at astro.psu.edu>

authors: D. Grupe (PSU), D. Burrows (PSU)., D. Morris (PSU),
T. Sakamoto (GSFC), N. Cucchiara (PSU), A. Retter (PSU),
S. Barthelmy (GSFC)
on behalf of the Swift team

We report on the analysis of the X-ray source Swift J061223.0+701243.9
which is inside the  Field of view of BAT trigger 180274
(GRB 060204C).
As discussed by Grupe et al (GCN 4672) this source
is about 8' away from the BAT position reported by Grupe et al.
(GCN 4663). The XRT position of this source is:
RA-2000:   06 12 22.97
Dec-2000: +70 12 43.9
with an error radius of 3.6"
Note that even though there was a star tracker loss-of-lock during
the initial trigger, we consider this position as very reliable. The
total exposure time of the field is 22.6 ks which were acquired
within 58.2 ks.

The light curve initially shows a brightening followed by a
decreasing count rate starting about 10 ks after the trigger.
Below we list the light curve with time after the trigger
(in seconds), count rate and count rate error (in units of XRT
counts/s):

Time          cr     cr_err      
------------  -------  ----------
 2.61399e+02   1.82e-02  7.03e-03
 5.25616e+03   5.94e-02  4.88e-03
 1.10075e+04   6.39e-02  5.06e-03
 1.68026e+04   3.43e-02  3.65e-03
 2.18468e+04   5.66e-02  6.91e-03
 2.75906e+04   5.16e-02  7.24e-03
 3.43580e+04   2.06e-02  2.92e-03
 4.03060e+04   4.35e-02  4.20e-03
 4.61773e+04   3.19e-02  3.61e-03
 5.20307e+04   2.07e-02  2.89e-03
 5.63931e+04   2.23e-02  3.34e-03
 
 The spectral analysis shows excess absorption above the Galactic
 value (9e20 cm-2) with 18.8+2.9-6.1 with a photon index
 Gamma = 1.52+0.16-0.15. Because we do not know the nature of this
 X-ray transient source (it was not present in the ROSAT All-Sky
 Survey) we encourage optical observers to derive a spectrum
 to identify the source.
 
 Due to the distance of 8' away from the BAT position we do not
 consider this X-ray source an afterglow of GRB 060204C.
 As discussed by Sakamoto et al (GCN 4679) BAT trigger 180274 is
 most likely not a real GRB and probably a hard X-ray transient.  
 We have no further plan to re-observe the field of BAT trigger
 180274.