Accretion disk and stream origin of the dip phenomenon in Hercules X-1

Abstract

Abstract. The Rossi X-ray Timing Explorer has observed Hercules X-1 over a period of about 13 years, allowing detailed measurement of the properties of the dip phenomenon. We construct a model for the dips based on the impact between the accretion stream and the disk, including the geometry and dynamics of the stream and disk. We also consider the case where the stream penetrates the outer parts of the disk, where its density is low, and proceeds to a second impact at smaller radius in the disk. The results from the model are discussed and compared to the observed properties of the dips.