[vsnet-grb-info 16885] GRB 150818A: Swift-XRT update, correction to GCN 18162

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18166
SUBJECT: GRB 150818A: Swift-XRT update, correction to GCN 18162
DATE:    15/08/19 07:17:42 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

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

Due to a computer error, the light curve decay index was missing in GCN 
18162.

At the present time, we have analysed 7.6 ks of XRT data for GRB 150818A 
(D'Elia et al. GCN Circ. 18152), from 74 s to 44.1 ks after the BAT trigger.

The XRT light curve can be modelled as a broken power-law, with an 
initial decay index of 2.36 (+0.08, -0.06), a break at T0 + 3600 
(+/-500) s, and a subsequent shallow decay of 0.66 (+0.16, -0.15).

If the decay continues at alpha=0.66, the predicted count-rate at T0+24 
hrs is 8.9e-3 ct/sec, which corresponds to an observed (unabsorbed) 
0.3-10 keV flux of 2.97e-13 (3.56e-13) erg/cm^2/s.

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