TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5139 SUBJECT: GRB 060515: Swift/XRT Team refined analysis DATE: 06/05/15 13:50:58 GMT FROM: Kim Page at U.of Leicester K.L. Page, J.P. Osborne (U. Leicester), J.A. Kennea, A. Cucchiara (PSU) & J.R. Cummings (NASA/ORAU) report on behalf of the Swift/XRT team: We have analysed the first 4 orbits of Swift/XRT data of GRB 060515 (trigger number 210084; Cummings et al., GCN 5132), which equates to 9.6 ks between 3.4 ks and 23.2 ks after the trigger. The source tentatively identified by Page & Kennea in GCN 5137 is found to be fading, and so is the best candidate for the afterglow. The refined position is: RA(J2000) = 08 29 09.5 Dec(J2000) = +73 34 02.82 with an estimated uncertainty of 4.5 arcsec (90% uncertainty). This is 1.3 arcsec from the preliminary XRT given in GCN 5137, but 68.3 arcsec from the possible optical candidate suggested by TAROT (GCN 5314, Klotz et al.). The source is only detected in the first 2 individual orbits of data, giving a decay slope of alpha = 1.2 +/- 0.6. However, between the 2nd and 3rd orbits, the slope must steepen, since the 3-sigma upper limit on the count rate (1.4e-3 count s^-1) is well below the extrapolation of alpha = 1.2. Thus, we cannot sensibly predict the flux at 24 hours. However, between 3.4 ks - 5.9 ks, the 0.3-10 keV observed (unabsorbed) flux was 1.45e-12 (1.51e-12) erg cm^-2 s^-1. This circular is an official product of the Swift/XRT team.