X-ray study of the NGC 383 group of galaxies and the source 1E 0104+3153

We present results from an analysis of the X-ray properties of the NGC 383 galaxy group based on ROSAT PSPC and HRI data. X-ray emission can be traced out to similar to 1h(50)(-1) Mpc, the estimated virial radius of the syste m. We determine a total mass of 6 10(13)h(50)(-1) M. for the group inside t his radius with a gas mass fraction of 21%. The intragroup gas temperature of 1.5 keV is both consistent with the galaxy velocity dispersion and the X -ray luminosity - temperature relation of groups and clusters suggesting th at the group is fairly relaxed. This is also indicated by the almost spheri cally symmetric appearance of the group's X-ray halo. The X-ray properties of the radio galaxy NGC 383 (3C 31) which is located n ear the center of the group are discussed. Its spectrum is best described b y a two-component model, consisting of emission from a low-temperature Raym ond-Smith plasma, and a hard tail. The emission from NGC 383 is not resolve d by the ROSAT HRI. The possible interaction of the radio jets of 3C 31 wit h the IGM is studied. A spatial, spectral and temporal analysis of the Einstein source 1E0104+315 3 located within the field of view is performed, one goal being the identif ication of the optical counterpart (with both, a hi,oh-redshift BAL quasar and a nearby elliptical galaxy, member of a small group, located within the Einstein X-ray error circle). We find evidence that the IGM of the small g roup contributes significantly to the X-ray emission of 1E0104, which can b e described by a Raymond-Smith model of kT similar or equal to 2 keV and a soft X-ray luminosity of L-x similar or equal to 3 10(43) erg/s.