[vsnet-grb-info 7795] GRB 090510: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9341
SUBJECT: GRB 090510: Swift XRT refined analysis
DATE:    09/05/10 15:41:02 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe at astro.psu.edu>

D. Grupe (PSU) and E. Hoversten (PSU) report on behalf of the Swift- 
XRT team:

We have analysed  XRT data for GRB090510 (Hoversten et al. GCN Circ.  
9331) up to
25ks after the burst
beginning 94.1 s after the BAT trigger. The data comprise 200 s in  
Windowed
Timing (WT) mode and 9.7 ks in Photon Counting (PC) mode.
The enhanced XRT position for this burst was given by Goad et al.
(GCN. Circ 9339).

The light curve can be modelled with a broken power-law decay with an
index of alpha=0.77+/-0.05, followed by a break at T+1470+/-160 s to
an alpha of 2.16 (+0.17, -0.14).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.57+/-0.08 with an
absorption column consistent with the Galactic
value of 1.66 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum
is consistent with this result.


If the light curve continues to decay with a power-law decay index of  
2.16,
the count rate at T+24 hours will be 1.3e-4 counts/s, corresponding to  
an
observed  0.3-10 keV flux of 6.1 x 10^-15 erg cm^-2 s^-1.



The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00351588.

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