BL ERI - an almost-contact binary system

BV photoelectric and spectroscopic observations of the 0.417-day-period eclipsing binary BL Eri were made. Light curves show total eclipses and a considerable photometric disturbance. The light-curve analysis reveals that both components are noncontact but nearly fill their respective critical Roche lobes, and the system is almost contact. The spectral type is determined to be around G0 V. The spectrum appears double lined, giving a spectroscopic mass ratio that is in accord with the photometric mass ratio (q = 0.54). The components are undermassive for their radii and luminosities, indicating a post-main-sequence evolutionary state of the system. (Author)