A survey for transient accretion disks in short-period Algol systems. II

Time-resolved spectroscopy during primary eclipse was utilized in order to search for emission lines from accretion disks surrounding the primary component in short-period Algol systems. The authors present the results of observations of 46 systems surveyed during 80 eclipses. When combined with an earlier survey this makes a total of 52 systems and 104 eclipses. A distinction is made between the disks in long-period systems and those in short-period systems. In the former case the gas stream from the secondary star moves around the trailing hemisphere of the primary and forms a permanent disk. However, in the latter case the gas stream strikes the primary star. Disks formed by this latter process are found to be transient and unstable. The authors report the discovery of two new transient disk systems: RW Mon and RR Dra. When the relative radius of the primary star is plotted versus mass ratio, the systems with permanent disks, transient disks, and without disks segregate into three distinct regions of the plot. This implies that the differences between systems with transient disks and those without disks may be simply a matter of the location of the stream impact on the primary star.