[vsnet-grb-info 23949] GRB 191019A: Swift-XRT updated analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26048
SUBJECT: GRB 191019A: Swift-XRT updated analysis
DATE:    19/10/20 20:12:27 GMT
FROM:    Boris Sbarufatti at PSU  <bxs60 at psu.edu>

B. Sbarufatti (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester) 
and K.K. Simpson (PSU) report on behalf of the Swift-XRT team:


We have analyzed 8.5 ks of XRT data for GRB 191019a (Simpson et al. GCN Circ. 26031), from 3.3 ks to 32.4 ks after the BAT trigger.
The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 26043).

The light curve can be modeled with a power-law decay with a decay index of alpha=1.0 (+/-0.2).

A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+/- 0.40). The
best-fitting absorption column is  consistent with the Galactic value of 3.3 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total intrinsic column:	    < 2.23 x 10^21 cm^-2
Galactic foreground: 3.3 x 10^20 cm^-2
Photon index:	    2.0 (+/- 0.4)

If the light curve continues to decay with a power-law decay index of 1.0, the count rate at T+48 hours will be 1.2 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.1 x 10^-14 (4.9 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/00930285/.

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