Outburst in U Cephei

Abstract

A SYSTEMATIC survey of the profiles of the Hα line in binary stars, shell stars, Be stars and related peculiar objects is being conducted by us (and G. J. Peters) with the Varo image intensifier attached to the coudé spectrograph of the 120-inch telescope and the 24-inch coudé auxiliary telescope of the Lick Observatory. Emission at Hα is found to be a more common Phenomenon among the Algol-type eclipsing binaries than was thought before. Usually, but not always, the emission is best observed during the primary minimum when the light of the hotter and brighter component is either greatly reduced or completely occulted. This is in agreement with the models representing the Algol systems as evolved binaries in which mass is still being transferred from the late-type secondary component to the hotter primary star^1,2. Although the general picture is fairly clear, the problem remains how the on-flowing material and its angular momentum are distributed among the primary star, the disk revolving around it and a possible envelope enclosing the whole system. The purpose of our survey is to furnish quantitative data on this process.