A GRAVITATIONAL LENS CLUSTER ABELL-2104 DISCOVERED IN THE ROSAT ALL-SKY SURVEY SAMPLE

We report the discovery of a new gravitational arc in the bright X-ray cluster A2104, in the course of a photometric and spectroscopic surve y of a sample of ROSAT clusters. The arc is located very close to the cluster center and appears redder than previously known giant arcs. Gl obal cluster optical properties and detailed morphological study of th e cD and the arc are presented. The X-ray emission is also analysed an d a two component decomposition is suggested. The cluster morphology s hows a marked preferential direction both in optical and X-rays. Impli cations for the cluster matter distribution are discussed.