[vsnet-grb-info 8854] GRB 100115A: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10352
SUBJECT: GRB 100115A: Swift-XRT refined analysis
DATE:    10/01/20 08:55:01 GMT
FROM:    Raffaella Margutti at U. di Milano Bicocca  <raffaella.margutti at brera.inaf.it>

R. Margutti, B. Sbarufatti (INAF-OAB), S. Oates (MSSL/UCL),
report on behalf of the Swift-XRT team:

The Swift ToO observations of the BATSS burst GRB 100115A
(Cummings et al., GCN Circ. 10325) started  40ks  after the
trigger. The XRT data set consists of 8 ks exposure in PC mode
split into two epochs: the first observation was performed
at T0+40 ks, while a second epoch of observations was acquired
at T0+306 ks. The UVOT-enhanced XRT position was given by
Margutti et al. in GCN Circ. 10334.

In the second observation the X-ray source reported by Margutti
et al., GCN Circ.10326 has faded to a level of (1.4 +/- 0.9)e-3
count/sec corresponding to a decay index of -0.7 +/- 0.4.
This source is likely to be the afterglow of GRB 100115A.
No further observations are planned.

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.0 (+1.0, -0.5). The
best-fitting absorption column is consistent with the Galactic value
of 3.1 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum
is 3.4 x 10^-11 (3.8 x 10^-11) erg cm^-2 count^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020126.

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