Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 6702

GRB 070802: Swift-XRT refined analysis
2007-08-02T19:48:18Z (17 years ago)
Vanessa Mangano at INAF-IASFPA <>
V. Mangano, B. Sbarufatti, V. La Parola, E. Troja (INAF-IASF PA),
P. Evans (U. Leicester) and S. Immler (GSFC)
report on behalf of the Swift-XRT team:

We have analysed the first three orbits of Swift-XRT data obtained for
GRB 070802 (Barthelmy et al, GCN Circ. 6692), which include 3.4 ks of
Photon Counting (PC) data.

Using 599 s of overlapping XRT Photon Counting mode and UVOT V-band
data, we find an astrometrically corrected X-ray position (using the
XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 36.89899, -55.52733 which is equivalent to:

RA (J2000):  02 27 35.76
Dec (J2000): -55 31 38.4

with an uncertainty of 2.1 arcsec (radius, 90% confidence).
This is 4.9 arcsec from the initial XRT position (Evans and Mangano,
GCN Circ. 6697) and 38 arcsec from the BAT ground-calculated position
(Cummings et al, GCN Circ. 6699). It is also 0.7 arcsec from the
optical position of Malesani et al. (GCN Circ. 6696) and 1.4 arcsec
from the I band position of Berger and Murphy (GCN Circ. 6695).

The XRT light-curve decays with slope -2.0+/-0.2 up to about T+500 s,
then flattens to slope -0.25+/-0.08. We do not see a further break up
to T+17 ks.

The spectrum can be fit with an absorbed power law with
a photon index of 1.9+/-0.3 and a column density consistent
with the Galactic value (2.9e20 cm^-2).
The absorbed (unabsorbed) 0.3-10.0keV flux for the spectrum is
(3.9+/-0.8)e-12 ((4.6+/-0.8)e-12) ergs cm^-2 s^-1.

If the decay continues with a slope of ~ 0.2, the count rate at 24
hours is predicted to be 3e-2 count s^-1. Using the spectral fit
described above, this corresponds to an observed flux of about
1.4e-12 ergs cm^-2 s^-1.

This circular is an official product of the XRT team.
Looking for U.S. government information and services? Visit