Spectrophotometry of peculiar shell star HD 218393

Abstract

HD 218393 is a well known shell star having several interesting spectral features. Struve (1944), Merrill (1949), Holliday (1950) and Doazan and Peton (1970) observed this star spectroscopically and noticed a series of changes in the spectrum. The radial velocity variations of the circumstellar lines suggested a period of 35 to 40 days but the amplitude was not exactly the same. Doazan and Peton (1970) interpreted the radial velocity variations as caused by an expanding envelope with variable accelerations, while after analysing all the available radial velocity data of HD 218393, Kriz and Harmanec (1975) suggested that the object may be an interacting binary with a possible orbital period of 38.873d.