[AAVSO-HEN] GRB100111A: Swift-XRT refined analysis

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  10320
SUBJECT: GRB100111A: Swift-XRT refined analysis
DATE:    10/01/11 16:53:52 GMT
FROM:    Loredana Vetere at PSU  <vetere at astro.psu.edu>

L. Vetere (PSU) reports on behalf of the Swift-XRT team:


We have analysed 774 s of XRT data for GRB 100111A (Vetere et al.
GCN Circ. 10317), from 77 s to 852 s after the BAT trigger. The
data are entirely in Photon Counting (PC) mode. The light curve
can be modelled with a power-law decay with a decay index of
alpha=0.58 +/- 0.16.

A spectrum formed from the PC mode data can be fitted with an
absorbed power-law with a photon spectral index of 2.10 (+0.29,
-0.26). The best-fitting absorption column is 1.7 (+0.8, -0.7) x
10^21 cm^-2, in excess of the Galactic value of 4.1 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 3.8 x
10^-11 (5.7 x 10^-11) erg cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index
of 0.58, the count rate at T+24 hours will be 0.023 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x
10^-13 (1.3 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/00382399.

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