[vsnet-grb-info 14792] GRB 140413A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16106
SUBJECT: GRB 140413A: Swift-XRT refined Analysis
DATE:    14/04/14 11:39:30 GMT
FROM:    Luca Izzo at ICRA  <Luca.Izzo at ICRA.it>

L. Izzo (URoma/ICRA) and V. D'Elia (ASDC) report on behalf of the
Swift-XRT team:

We have analysed 13 ks of XRT data for GRB 140413A,  from 2.2 ks to
83.3 ks after the  BAT trigger. The data comprise 2.1 ks in Windowed
Timing (WT) mode with the remainder in Photon Counting (PC) mode. Using
3951 s of PC mode data and 4 UVOT images, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 65.45475, -51.18310 which is
equivalent to:

RA (J2000): 04h 21m 49.14s
Dec(J2000): -51d 10' 59.2"

with an uncertainty of 1.6 arcsec (radius, 90% confidence).

The late-time light curve (from T0+38.1 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.7 (+/-0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.989 (+0.025, -0.024). The
best-fitting absorption column is  4.04 (+/-0.13) x 10^21 cm^-2, in
excess of the Galactic value of 1.4 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 3.9 x 10^-11 (6.0 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     4.04 (+/-0.13) x 10^21 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: 49.9 sigma
Photon index:	     1.989 (+0.025, -0.024)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00595616.

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