GCN Circular 6400
Subject
GRB070509: Swift-XRT Refined Analysis
Event
Date
2007-05-09T22:09:02Z (19 years ago)
From
Loredana Vetere at PSU <vetere@astro.psu.edu>
L. Vetere, J. L. Racusin, D. Grupe, C. Pagani (PSU) and M. Perri (ASDC) report
on behalf of the Swift Team:
We have analysed the first 6.2ks of Swift XRT data from GRB
070509 (trigger number 278903, GCN 6394).
The first orbit Photon Counting mode image (1.5ks) provides a
refined XRT position at
RA,DEC(J200) = 237.9588, -78.6508 which is
RA(J2000) = 15h 51m 50.1s
Dec(J2000) = -78d 39' 03.1"
with an uncertainty of 4.1 arcsec (radius, 90% containment).
This is 0.9 arcsec from the initial X-ray position (GCN 6394)
and 1.0 arcmin from BAT refined position (Cummings et al. GCN 6397).
The XRT light curve can be modeled with a broken power law with the
following parameters:
alpha1= -0.3 +/- 0.2
tbreak= 341 +/- 120
alpha2= -1.1 +/- 0.2
The X-ray spectrum of the first orbit PC data can be fitted with an
absorbed power law (photon index = 0.8+/-0.2) with an absorbed column
density fixed to the Galactic value (0.91e21 cm^-2; Dickey & Lockman,
1990). The absorbed (unabsorbed) 0.3-10.0keV flux for this spectrum
was 8.8E-12 (9.1E-12) ergs cm^-2 s^-1.
Assuming the source continues to decay at the same rate, we predict
an XRT count rate of 3.5E-4 counts/s at T+24 hours, which corresponds
to an observed (unabsorbed) flux of 5.1E-14 (5.3E-14) ergs cm^-2 s^-1.
This circular is an official product of the Swift XRT team.