[vsnet-grb-info 14902] GRB 140430A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16197
SUBJECT: GRB 140430A: Swift-XRT refined Analysis
DATE:    14/05/01 09:48:09 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

M.C. Stroh (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), C.
Pagani (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri
(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), P. D'Avanzo (INAF-OAB), J.A.
Kennea (PSU) and M.H. Siegel report on behalf of the Swift-XRT team:

We have analysed 7.0 ks of XRT data for GRB 140430A (Siegel  et al. GCN
Circ. 16190),  from 132 s to 23.5 ks after the	BAT trigger. The data
comprise 382 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 16195).

The late-time light curve (from T0+3.8 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.68 (+0.12, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.05 (+/-0.04). The
best-fitting absorption column is  3.7 (+1.4, -1.3) x 10^21 cm^-2, at a
redshift of 1.6, in addition to the Galactic value of 2.1 x 10^21 cm^-2
(Willingale et al. 2013). The PC mode spectrum has a photon index of
2.21 (+0.20, -0.19) and a best-fitting absorption column of 5.3 (+6.5,
-5.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum  is 3.3 x 10^-11 (5.2
x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.1 x 10^21 cm^-2
Intrinsic column:    5.3 (+6.5, -5.3) x 10^21 cm^-2 at z=1.6
Photon index:	     2.21 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
0.68, the count rate at T+24 hours will be 0.018 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.0 x
10^-13 (9.6 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/00597722.

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