[vsnet-grb-info 8954] GRB 100219A: XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10444
SUBJECT: GRB 100219A: XRT refined analysis
DATE:    10/02/20 07:11:16 GMT
FROM:    Antonia Rowlinson at U.of Leicester  <bar7 at star.le.ac.uk>

A. Rowlinson (U Leicester) reports on behalf of the Swift-XRT team:

We have analysed 3.8 ks of XRT data for GRB 100219A (Rowlinson et al.
GCN Circ. 10430), from 207 s to 28.4 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Evans et al. (GCN. Circ 10437).

The light curve can be modelled with an initial power-law decay with an
index of alpha=1.53 (+0.28, -0.22), followed by a break at T+785 s to an
alpha of 0.57 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.72 (+0.16, -0.13). The
best-fitting absorption column is 8.8 (+4.2, -0.0) x 10^20 cm^-2, in
excess of the Galactic value of 6.5 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.5 x 10^-11 (5.3 x 10^-11) erg
cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of
0.57, the count rate at T+24 hours will be 0.035 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-12 (1.8 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00412982.
This circular is an official product of the Swift-XRT team.