TITLE:   GCN CIRCULAR
NUMBER:  9674
SUBJECT: GRB 090715B: Swift XRT Refined Analysis
DATE:    09/07/16 05:45:40 GMT
FROM:    Loredana Vetere at PSU  <vetere@astro.psu.edu>

L. Vetere (PSU) reports on behalf of the Swift-XRT team:

We have analysed ~2 ks of XRT data for GRB 090715B (Vetere et al. GCN
Circ. 9668), from 52 s to 10.2 ks after the BAT trigger. The data
comprise 471 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The refined XRT position for this burst is
Ra, Dec 251.340   44.838 which is:

    RA(J2000) = 16h 45m 21.7s
    Dec(J2000) = +44d 50' 18.1"

The light curve shows multiple peaks in WT and a power-law decay in PC  
with a
decay index of alpha=1.1(+/-0.2).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.84 (+/-0.02). The
best-fitting absorption column is 1.09 (+/-0.02) x 10^21 cm^-2, in
excess of the Galactic value of 1.3 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.3 (+/-0.3) and a
best-fitting absorption column of 1.4 (+/-0.1) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.8 x 10^-11 (5.8 x 10^-11) erg cm^-2
count^-1.

If the light curve continues to decay with a power-law decay index of
1.1, the count rate at T+24 hours will be 0.02 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.6 x
10^-13 (1.2 x 10^-12) erg cm^-2 s^-1.

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