[vsnet-grb-info 26654] GRB 201021C: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28754
SUBJECT: GRB 201021C: Swift-XRT refined Analysis
DATE:    20/10/22 20:40:03 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), P. D'Avanzo (INAF-OAB), M.G.
Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , J. D. Gropp (PSU),
J.A. Kennea (PSU) and A.Y. Lien report on behalf of the Swift-XRT team:

We have analysed 4.3 ks of XRT data for GRB 201021C (Lien et al. GCN
Circ. 28730), from 105 s to 58.8 ks after the  BAT trigger. The data
comprise 62 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Beardmore et al. (GCN Circ. 28736).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.22 (+0.07, -0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.62 (+0.19, -0.16). The
best-fitting absorption column is  5 (+21, -5) x 10^20 cm^-2, at a
redshift of 1.07, in addition to the Galactic value of 2.0 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 4.0 x
10^-11 (4.2 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.0 x 10^20 cm^-2
Intrinsic column:    5 (+21, -5) x 10^20 cm^-2 at z=1.07
Photon index:	     1.62 (+0.19, -0.16)

If the light curve continues to decay with a power-law decay index of
1.22, the count rate at T+24 hours will be 2.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (1.1 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01001130.

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