GCN Circular 10507
Subject
GRB 100316C: Swift-XRT team refined analysis
Event
Date
2010-03-16T19:15:43Z (16 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) and M. Stamatikos (OSU/NASA/GSFC) report on
behalf of the Swift-XRT team:
We have analysed 5.7 ks of XRT data for GRB 100316C (Stamatikos et al. GCN
Circ. 10491), from 87 s to 13.5 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. 10506).
The light curve can be modelled with a doubly-broken power-law, with
alpha1 = 0.28 (+0.66,-1.18) until T = 258 (+87/-66) s after the trigger,
at which point the decay steepens to alpha2 = 2.53 (+1.18, -0.44). At T =
883 (+1857, -271) s, the decay flattens to alpha3 = 0.76 (+0.27, -0.26).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.6 (+0.5, -0.4). The best-fitting
absorption column is 1.8 (+1.6, -1.3) x 10^21 cm^-2, in excess of the Galactic
value of 3.9 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
5.1 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of 0.76, the
count rate at T+24 hours will be 0.0013 count s^-1, corresponding to an
observed (unabsorbed) 0.3-10 keV flux of 6.6 x 10^-14 (8.1 x 10^-14) erg cm^-2
s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00416115.
This circular is an official product of the Swift-XRT team.