CIRCUMSTELLAR MATERIAL IN ALGOL - A STUDY OF THE BALMER LINE-PROFILES

The kinematics and spatial distribution of the circumstellar H II structures in Algol (beta Persei) have been found from a study of the Balmer Halpha, Hbeta, and Hgamma line profiles. The main focus of the study was the Halpha line profile which contained contributions from the circumstellar material. Since these contributions were weak, they were enhanced by removing the composite theoretical photospheric line profiles of the three stars in Algol from the observed line profile. These residual or difference profiles were studied to provide a model for the circumstellar gas in Algol. The 98 IIIa-F (4700-6700 angstrom) photographic spectra which were used in the analysis were obtained over 15 months during 1976 and 1977 and cover the entire orbit of the Algol binary, with a resolution of approximately 0.02 in phase. This single data set is more comprehensive than any other spectroscopic observations of beta Persei in the literature. Furthermore, these full-orbit observations constitute a new direction in the study of Algol-type binaries because they can be used to provide two-dimensional information about the circumstellar material. An additional 94 IIa-O and IIIa-J (3900-4900 angstrom) photographic spectra were obtained in 1972 and 1985 for the purpose of refining the stellar properties and to check the procedure which was used to calculate the composite theoretical line profiles. The orbital parameters and stellar properties assumed for the calculation of the composite theoretical photospheric spectrum of the stars were either obtained from the literature or from extensive analyses of multicolor light curves (reported earlier), IIa-O and IIIa-J spectra, and Hgamma line profiles of Algol. The spectral analysis performed in this work showed that the temperature of Algol A is 13,000 +/- 500 K; Algol C is a marginal Am star with both hydrogen- and metallic-line spectral types of F1 +/- 1, and an effective temperature of 7000 +/- 200 K; and the circumstellar material has a significant effect on the Hgamma line profile and changed its character between 1972 and 1985. The Halpha difference spectra contain emission and absorption components which arise primarily from a transient, high-density (N(e) greater than or similar to 10(11) cm-3), low-mass (M approximately 10(-13) M.), localized H II region. In the orbital plane of the binary, this region is located above the photosphere of the primary in the space between the two stars, roughly between the line of centers of the binary and the expected position of the gas stream. This region also extends beyond the orbital plane to a height comparable to the radius of the primary. The localized region can be understood in terms of the interaction between the gas stream from the secondary and material which circled the primary. This region is observationally indistinguishable from a gas stream except that gas streams are unlikely to be found high above the orbital plane. In addition, there is a low-density transient asymmetric rotating accretion disk which contains a high-velocity region.