On the nature of X Persei - Evidence from the 1957 outburst.
Discussion of the line identifications, radial velocities, and equivalent widths derived from spectrograms obtained with the University of Michigan 37-1/2-in. reflector and two-prism spectrograph between November 1954 and March 1960 by several observers. In mid-1957, there occurred in the spectrum of the O star X Per abrupt changes in the emission-line radial velocities and V/R ratios. The irregular variation of the V/R ratio, also observed in the past, suggests the occasional interruption of a more or less steady infall of material through the rotating emission region by outbursts of material from the star. The space velocity of X Per has been rederived, using a revised radial velocity, and compared to the space velocity of the runaway O star xi Per.