GCN Circular 6400
L. Vetere, J. L. Racusin, D. Grupe, C. Pagani (PSU) and M. Perri (ASDC) report on behalf of the Swift Team: We have analysed the first 6.2ks of Swift XRT data from GRB 070509 (trigger number 278903, GCN 6394). The first orbit Photon Counting mode image (1.5ks) provides a refined XRT position at RA,DEC(J200) = 237.9588, -78.6508 which is RA(J2000) = 15h 51m 50.1s Dec(J2000) = -78d 39' 03.1" with an uncertainty of 4.1 arcsec (radius, 90% containment). This is 0.9 arcsec from the initial X-ray position (GCN 6394) and 1.0 arcmin from BAT refined position (Cummings et al. GCN 6397). The XRT light curve can be modeled with a broken power law with the following parameters: alpha1= -0.3 +/- 0.2 tbreak= 341 +/- 120 alpha2= -1.1 +/- 0.2 The X-ray spectrum of the first orbit PC data can be fitted with an absorbed power law (photon index = 0.8+/-0.2) with an absorbed column density fixed to the Galactic value (0.91e21 cm^-2; Dickey & Lockman, 1990). The absorbed (unabsorbed) 0.3-10.0keV flux for this spectrum was 8.8E-12 (9.1E-12) ergs cm^-2 s^-1. Assuming the source continues to decay at the same rate, we predict an XRT count rate of 3.5E-4 counts/s at T+24 hours, which corresponds to an observed (unabsorbed) flux of 5.1E-14 (5.3E-14) ergs cm^-2 s^-1. This circular is an official product of the Swift XRT team.