TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4565 SUBJECT: GRB 060121: Swift XRT refined analysis DATE: 06/01/22 18:46:38 GMT FROM: Pat Romano at OAB-Swift V. Mangano, V. La Parola, T. Mineo (INAF-IASFPA), P. O'Brien (UL), P. Romano (INAF-OAB), D.N. Burrows (PSU), M. Chester (PSU), L. Angelini (GSFC) on behalf of the Swift XRT team: The Swift XRT instrument began observing the HETE-discovered GRB 050121 (Arimoto et al., GCN 4550; Prigozhin et al., GCN 4551) at 01:21:37 UT on 22 January 2006 (Mangano et al., GCN 4560) 10.6 ks after the burst. Further analysis of the first 5 ks of XRT data of GRB 060121 spanning three orbits (Mangano et al., GCN 4560) revealed that the source is fading with a power law decay index of -1.08 + / - 0.24. The average spectrum is well fitted by an absorbed power law model with a photon index of 2.07 + / - 0.25 (90% confidence level). The best fit absorption column of (7.8 + / - 4.5)e20 cm^-2 is slightly in excess of the Galactic absorption column of 1.7e20 cm^-2. The average unabsorbed 0.2-10 keV flux in the time range 10.6 - 22 ks after the trigger is at the level of 4.6e-12 ergs cm^-2 s^-1. The predicted flux at 24 hours after the trigger is at the level of 6.8e-13 ergs cm^-2 s^-1 (corresponding to a count rate of about 1.1e-2 counts/s). New observations are being performed. According to NED, the nearest two galaxies with known redshifts are SDSS J091016.39+453819.9 and SDSS J091023.53+454159.8 with a redshift of 0.154357 and 0.154272, respectively. They are 4.5 and 6 arcmin from the Swift GRB position (Mangano et al., GCN 4560).