TITLE: GCN CIRCULAR NUMBER: 8758 SUBJECT: GRB081230: Swift-XRT refined analysis DATE: 08/12/31 14:23:44 GMT FROM: Valentina La Parola at INAF-IASPA V. La Parola, B. Sbarufatti, V. Mangano (INAF-IASF Pa) report on behalf of the Swift XRT team: We have analysed the first 35 ks of XRT observations for GRB 081230 (La Parola et al. GCN Circ 8753), with an exposure time of 104 s in WT mode and 11.4 ks in PC mode. The astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 37.3314 -25.1477, corresponding to: RA (J2000): 02h 29m 19.53s Dec (J2000): -25d 08' 51.8 with an uncertainty of 1.8 arcsec (radius, 90% confidence, Osborne et al. GCN Circ 8756). The lightcurve can be fitted with a broken power-law with the following parameters: alpha1=-6.910+/-0.007 T_break=298+/-9 alpha2=-0.62+/-0.5 There is evidence for a late flare a peaking at 5000s. The spectrum of the data collected in WT mode can be fitted with a powerlaw with photon index Gamma = 1.96 +/- 0.11, absorbed by the Galactic column in this direction of 1.7x10^20 cm^-2, plus an intrinsic column of (6.4+/-2.2)x10^20 cm^-2. The observed (unabsorbed) flux over this time is 1.03x10^-9 (1.3x10^-9) erg cm^-2 s^-1, corresponding to a counts to observed flux conversion of 4.1x10^-11 erg cm^-2 count^-1. The spectrum of the data collected in PC mode can be fitted with a powerlaw with photon index Gamma = 2.14 (+0.10,-0.20), with an intrinsic column of (5.3 [+2.2,-3.7])x10^20 cm^-2. The observed (unabsorbed) flux over this time is 2.1x10^-12 (2.7x10^-9) erg cm^-2 s^-1, With the present decay law, the count rate at 24 hours is predicted to be 1.1x10^-2 c/s (corresponding to an observed flux of 3.7x10^-13 erg cm^-2 s^-1) This circular is an official product of the Swift-XRT team. I.A.S.F. INAF Mailing System Outgoing mail is certified Virus Free. Checked by McAfee anti-virus system