GCN Circular 9368
A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team : We have analysed 4.5 ks of XRT data for GRB 090515 (Beardmore et al. GCN Circ. 9356), from 70 s to 11.5 ks after the BAT trigger. The data comprise 132 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 9367). Initially, the light curve follows a shallow decay from a rate of 30 count s^-1 (at T+70 s), with a decay index of 0.59, out to approximately T+245 s. The count rate then drops by a factor of ~250 in the next ~70 s (i.e. suggesting a decay index in excess of 10 at this time). The burst is no longer detected beyond the first orbit to a 3 sigma count rate upper limit of 0.0058 count s^-1 (from T+5.7 to T+11.5 ks). A spectrum formed from the WT mode data (from T+70 to T+195 s) can be fitted with an absorbed power-law with a photon spectral index of 1.88 +/- 0.14. The best-fitting absorption column is (6.1 +3.0 -2.8) x 10^20 cm^-2, in excess of the Galactic value of 1.9 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 3.6 x 10^-11 (4.1 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/00352108. This circular is an official product of the Swift-XRT team.