TITLE:   GCN CIRCULAR
NUMBER:  36071
SUBJECT: GRB 240411B: Swift-XRT refined Analysis
DATE:    24/04/12 16:36:29 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

P. D'Avanzo (INAF-OAB), J. D. Gropp (PSU), S. Dichiara (PSU), J.A.
Kennea (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA)  and
P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 3.9 ks of XRT data for GRB 240411B, from 160 s to 74.6
ks after the  BAT trigger. The data comprise 10 s in Windowed Timing
(WT) mode (taken while Swift was slewing), with the remainder in Photon
Counting (PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.66 (+0.12, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.13 (+0.38, -0.20). The
best-fitting absorption column is  consistent with 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 3.2 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.1 (+/-1.0) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.13 (+0.38, -0.20)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01221183.

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