NARROW- AND INTERMEDIATE-BAND HΑ AND O I Λ7774 PHOTOMETRY ANDRETICON SPECTROSCOPY OF SX CASSIOPEIAE.

Abstract

ABSTRACT Observations of the 36.57-day eclipsing binary SX Cas made on eight nights during February and March 1979 with pairs of intermediate- and narrow-band filters centered on the wavelengths of the Balmer H-alpha line and the O I 7774 A triplet are discussed. In addition, a reticon spectrum covering a wavelength range of 4750 A to 7700 A was obtained in September 1979, showing strong H-beta and H-alpha emission lines as well as absorption features of the K-giant component of the system. From the photometry, strong H-alpha emission is found at all the orbital phases sampled. However, no appreciable O I 7774 A line emission is detected. It is noted that the strong H-alpha emission is consistent with the presence of significant amounts of circumstellar and circumbinary gas. From the observations, it appears that the H-alpha emitting region is centered chiefly on the primary component, but the gas is partially eclipsed by the larger cool giant during primary eclipse. The H-alpha-emitting region therefore appears larger than the dimensions of the stellar components. In addition, the apparent nonrepeatability of the H-alpha emission strength from one orbital cycle to the next implies that relatively rapid changes in the extent or quantity of gas occur in the system.