TITLE: GCN CIRCULAR NUMBER: 7810 SUBJECT: GRB 080603A: Swift-XRT detection of the afterglow DATE: 08/06/04 16:08:03 GMT FROM: Boris Sbarufatti at INAF-IASF-Pa B. Sbarufatti, V. Mangano, V. La Parola (INAF-IASF Pa) report on behalf of the Swift-XRT team The Swift XRT began observations of the INTEGRAL burst GRB 080603A (Paizis et al., GCN Circ 7790) on June 3, 14:11 UT, 173 minutes after the trigger. The data consist of 3.9 ks observed in Photon Counting mode. We detect an X-ray counterpart at position (astrometrically corrected using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 279.40858, 62.74446 which is equivalent to: RA (J2000): 18 37 38.06 Dec (J2000): +62 44 40.1 with an uncertainty of 1.9 arcsec (radius, 90% confidence). The light curve is dominated by a flare-like structure which covers all the observed time interval, making it impossible to estimate the behaviour of the underlying continuum and to predict the evolution of the source. The spectrum can be fitted with a powerlaw with an intrinsic absorbing column of (8+/-5)e21 cm-2 at z=1.688 (Perley et al., GCN Circ 7791) and photon index 2.4 ±0.3. The observed (unabsorbed) 0.3-10 keV flux is 3.23 (3.57)e-12 erg cm-2 s-1. This circular is an official product of the Swift-XRT team.