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GCN Circular 23888

Subject
GRB 190211A: Swift-XRT refined Analysis
Date
2019-02-12T04:12:55Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri
(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows
(PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), K.L. Page (U.
Leicester) and F.E. Marshall report on behalf of the Swift-XRT team:

We have analysed 9.4 ks of XRT data for GRB 190211A (Marshall et al.
GCN Circ. 23883), from 205 s to 24.2 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The refined XRT
position is RA, Dec = 196.6588, +41.9671 which is equivalent to:

RA (J2000): 13 06 38.10
Dec(J2000): +41 58 01.5

with an uncertainty of 3.5 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.15 (+0.16, -0.21), followed by a break at T+1088 s to
an alpha of 1.11 (+0.05, -0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.94 (+0.11, -0.10). The
best-fitting absorption column is  7.1 (+2.6, -2.4) x 10^20 cm^-2, in
excess of the Galactic value of 1.7 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 (3.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     7.1 (+2.6, -2.4) x 10^20 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: 3.7 sigma
Photon index:	     1.94 (+0.11, -0.10)

If the light curve continues to decay with a power-law decay index of
1.11, the count rate at T+24 hours will be 9.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.2 x
10^-13 (3.7 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/00888648.

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