Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 28796

GRB 201026A: Swift-XRT refined Analysis
2020-10-27T22:56:03Z (4 years ago)
Phil Evans at U of Leicester <>
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi 
(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (ASDC), J.A. Kennea
(PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), K.L. Page (U.
Leicester) and S.B. Cenko report on behalf of the Swift-XRT team:

We have analysed 3.2 ks of XRT data for GRB 201026A (Cenko et al. GCN
Circ. 28784), from 85 s to 46.3 ks after the  BAT trigger. The data
comprise 361 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 28791).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.90 (+1.12, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.82 (+/-0.03). The
best-fitting absorption column is  4.84 (+0.22, -0.21) x 10^21 cm^-2,
in excess of the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.4 x 10^-11 (6.4 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     4.84 (+0.22, -0.21) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: 29.0 sigma
Photon index:	     1.82 (+/-0.03)

If the light curve continues to decay with a power-law decay index of
0.90, the count rate at T+24 hours will be 5.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x
10^-13 (3.6 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at

This circular is an official product of the Swift-XRT team.
Looking for U.S. government information and services? Visit