TITLE: GCN CIRCULAR NUMBER: 5746 SUBJECT: GRB 061021: Swift-XRT refined analysis DATE: 06/10/21 22:38:01 GMT FROM: Alberto Moretti at Obs Brera Merate A. Moretti (INAF-OAB), C. Guidorzi (Univ. Bicocca & INAF-OAB), P. Romano (INAF-OAB) S. Campana (INAF-OAB) report on behalf of the Swift-XRT team: We have analysed the first 3 orbits of Swift-XRT data obtained for GRB 061021 (trigger=234905, GCN 5743). The data consist of 189 s in Windowed Timing (WT) mode, starting 78 seconds after the BAT trigger and 5.5 ks in Photon Counting (PC) mode. Using PC data we obtain a refined position of: RA(J2000) = 09h 40m 35.87s Dec(J2000)= -21d 57' 07.2" with an estimated uncertainty radius of 5 arcsec (90% containment). This location is 3.8 arcseconds from the UVOT position (GCN 5745). The light-curve, initially, shows a steep decay (alpha1=2.1+/-0.1) up to a break at t_break=368+/-20.s. After the break, the afterglow shows a shallow decay (alpha2=0.55+/-0.03) up to the end of the third orbit (t=12.5 ks). At this point the observed count rate was 2.2 counts per second, corresponding to an unabsorbed flux of 1.4E-11 erg/cm2/sec. The spectrum formed from all the WT data can be modelled with a power-law of photon index Gamma = 1.88 +/- 0.07, with an absorbing column of NH = (3.4 +/- 0.8)E20 cm^-2 consistent with the Galactic value of 4.20E20 cm^-2. The spectrum formed from the PC data is slightly softer than the WT spectrum: it can be modelled with a power-law of photon index Gamma = 1.96 +/- 0.08. All errors are quoted at 90% confidence level. This circular is an official product of the Swift-XRT team.