[vsnet-grb-info 4201] GRB070107: Swift/XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6003
SUBJECT: GRB070107: Swift/XRT refined analysis
DATE:    07/01/08 22:12:04 GMT
FROM:    Teresa Mineo at INAF-IASFA  <teresa.mineo at ifc.inaf.it>

T. Mineo, B. Sbarufatti, V. Mangano, G. Cusumano (INAF-IASF Pa)
report on behalf of the Swift XRT team:

We have analyzed the first ten orbits of Swift-XRT data on GRB 070107
(Stamatikos et al. GCN 5999), with a total exposure of 420 s seconds
in Window Timing (WT) mode and 15.8 ks seconds in Photon Counting (PC) 
mode.
This provides a refined XRT position at RA,Dec=159.4016,-53.2131
which is:

RA (J2000) =  10h 37m 36.4s
Dec(J2000) = -53d 12m 47.3s

with an estimated error radius of 3.7 arcseconds (90% confidence).  This
position is 59.4 arcseconds from the  BAT refined position (Barthelmy et
al. GCN 6001), 2.6 arcseconds from the initial XRT position
(Kennea & Stamatikos, GCN 6000), and 0.4 arcseconds from the UVOT 
optical candidate (Boyd et al., GCN 6002).

The 0.3-10 keV X-ray light curve presents a bright flare starting at
about 300 s from the trigger and coincident with the peak detected in 
the BAT light curve (Barthelmy et al. GCN 6001). A second fainter peak 
is also present at 1300 s and the light curve between 3 ks and 59 ks
can be fit with a simple power-law with a decay slope of 1.05 ± 0.05.

The X-ray spectrum from the XRT/WT data, mainly covering the first 
bright flare, is well fit by an absorbed power-law with a photon index 
of 2.07±0.07 and column density of (3.8±0.2)e21 cm**-2, consistent
with the Galactic column density in the direction of the source
(3.6E21 cm**-2).  The unabsorbed 0.3-10 keV  flux for this spectrum is
1.3e-9 erg/cm**2/s. The XRT/PC data is modeled by an absorbed power law 
with a photon index of 2.2±0.1 and column density of (4.3±0.4)e21 cm**-2 
and the unabsorbed 0.3-10 keV flux  is 2.48E-11 erg/cm**2/s.

Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10 keV XRT count rate of 1e-2 count/s at T+48hr, which
corresponds to an observed 0.3-10 keV flux of 1.4e-12 erg/cm**2/s.

This circular is an official product of the Swift XRT Team.