[vsnet-grb-info 2144] GRB 050915: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3983
SUBJECT: GRB 050915: Swift XRT refined analysis
DATE:    05/09/15 18:14:14 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe at astro.psu.edu>

D. Grupe, J. Kennea, D. Burrows (PSU), and N. Gehrels GSFC) on report
behalf of the Swift XRT team:

We have analyzed the Swift XRT data of the first three orbits of  GRB050915
(Grupe et al. GCN 3977, BAT trigger 155242). The new refined position  
based
on the SDC quicklook data is:

RA (J2000) =  05h26m44.6s
DEC(J2000) = -28d01m01.0s

This position is 5.8 arcsec away from the XRT position reported by  
Kennea et al.
(GCN 3979) based on the preliminary data analysis and 29 arcsec from the
refined BAT position (Barthelmy et al., GCN 3982).

The WT data show a spectrum that can be fitted by a single power law  
with excess
absorption above the Galactic value. The X-ray energy spectral slope  is 
beta-x =
1.33+/-0.23. The integrated 0.3-10.0 keV Flux during the WT  observation 
was
4.6e-10 ergs/s/cm2 (corrected for absorption).

The XRT light curve started 87s after the burst and shows a rapidly  
decaying
source after a light increased in flux at the beginning. The decay  
slope is
alpha-1 = 3.00+/-0.14. The light curves shows a clear break in the PC  
mode data
at 210s after the burst and flattens to a decay slope alpha-2=0.75 ±0.04.
Extrapolating this light curve we estimate the 0.3-10.0 flux to be in  
the order
of 5e-13 ergs/s/cm2 24 hours after the burst. However, this estimate  
does not
take any late time break, which are usually observed in GRBs several  
hours after
the burst, into consideration.