UBV photometry of the eclipsing binary Zeta Phoenicis.
Abstract
200 photoelectric observations of Phe in the UBV system, along with recent radial velocity measurements by Popper (1970), are used to derive an improved set of elements of this eclipsing binary system with detached components. The colours of the components correspond to stars of spectral types B7V and B8.5V, respectively. The radii of the individual components of the system are: B1 = 2.96 + 0.05, B8 = 1.96 + 0.06 (solar radii). The observed radii are compared to radii computed from the theory of stellar interiors by various authors, for stars of masses as measured by Popper (1970) for the components of Phe (M1 = 3.85 + 0.2, M8 = 2.5 + 0.1 solar masses). The best agreement for the radii is obtained with the stellar models of Mathis (1967). The evolutionary age of the system is estimated from the increase of radii as compared to age zero models and is about 1.0 x 108 years. The observed values of the magnitudes and colours of the components of Phe and theoretical results for the luminosities and effective temperatures are discussed. A difference of the depths of the primary minimum which is a nearly grazing transit has been found between the spectral ranges V, B, and U. This difference of depths may be explained by a faint extended envelope surrounding the smaller component of the system and giving rise to continuous absorption in the U spectral band. The line of apsides has been found to rotate by at least 1200 or 2400 within 20 years. A rotation of the line of apsides of 2400 within 20 years is in quantitative agreement with the amount of apsidal motion predicted by Mathis (1967) for a system like Phe. Key words: eclipsing binaries - individual stars - stellar evolution
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 1971
- Bibcode:
- 1971A&A....12..286D