An X-ray and optical study of the cluster A33

We report the first detailed X-ray and optical observations of the medium-d istant, cluster A33 obtained with the Beppo-SAX satellite and with the UH 2 .2 m and Keck II telescopes at Mauna Kea. The information deduced from X-ra y and optical imaging and spectroscopic data allowed us to identify the X-r ay source 1SAXJ0027.2-1930 as the X-ray counterpart of the A33 cluster. The faint, F2-10 (keV) approximate to 2.4 10(-13) erg s(-1) cm(-2), X-ray sour ce 1SAXJ0027.2-1930, similar to 2 arcmin away from the optical position of the cluster as given in the Abell catalogue, is identified with the central region of A33. Based on six cluster galaxy redshifts, we determine the red shift of A33, z = 0.2409; this is lower than the value derived by Leir & Va n Den Bergh (1977). The source X-ray luminosity, L2-10 (keV) = 7.7 10(43) e rg s(-1) cm(-2), and intracluster gas temperature, T = 2.9 keV, make this c luster interesting for cosmological studies of the cluster L-X - T relation at intermediate redshifts. Two other X-ray sources in the A33 field are id entified. An AGN at z = 0.2274, and an hi-type star, whose emissions are bl ended to form an extended X-ray emission similar to 4 arcmin nor th of the A33 cluster. A third possibly point-like X-ray source detected similar to 3 arcmin north-west of A33 lies close to a spiral galaxy at z = 0.2863 and t o an elliptical galaxy at the same redshift as the cluster.