[vsnet-grb-info 4323] GRB 070219: XRT Refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6112
SUBJECT: GRB 070219: XRT Refined Analysis
DATE:    07/02/19 14:51:03 GMT
FROM:    Rhaana Starling at U of Leicester  <rlcs1 at star.le.ac.uk>

R.L.C. Starling (U Leicester), T. Sakamoto (NASA/GSFC), K.L. Page, M.R. 
Goad and P.A. Evans (U Leicester) report on behalf of the Swift-XRT team:

We have analysed the first four orbits (up to 18.8 ks after the BAT 
trigger) of Swift XRT data for the faint X-ray afterglow of GRB 070219 
(Sakamoto et al., GCN 6104). Using ~6 ks of Photon Counting (PC) mode data 
we find the following astrometrically corrected XRT refined position (by 
matching the UVOT images with the USNO-B1 catalogue):

RA (J2000)  =  17h 20m 45.99s 
Dec(J2000)  = +69d 22' 10.6"

with an error radius of 3.6 arcseconds (90% confidence). This is 95.2, 
21.8 and 3.0 arcseconds away from the BAT refined, BAT initial and XRT 
initial positions respectively.

The lightcurve appears to follow the canonical three-phase decay. It 
decays with alpha_1~2.2, breaking at T_bk_1~330 s to alpha_2~0.3 and 
breaking again at T_bk_2~9200 s to a slope of alpha_3~1.5.

The PC mode spectrum, summed over all the data collected thus far, is not 
tightly constrained, but can be fitted with a single power law of photon 
index Gamma = 2 and a total absorbing column at z = 0 of nH = 1.3E21 cm-2, 
in excess of the Galactic value of 4.1E20 cm-2. The 0.3-10 keV observed 
(unabsorbed) flux is 9E-13 (1.2E-12) erg/cm2/s. There are too few counts 
for a time-resolved spectral analysis, hence any spectral evolution 
present cannot be measured.

If the decay continues with a slope of alpha = 1.5, the predicted count 
rate at 24 hours post-trigger is 5E-4 cts/s. This corresponds to an 
observed (unabsorbed) flux of 2E-14 (3E-14) erg/cm2/s.

This circular is an official product of the Swift-XRT team.