Radii and masses for β Aurigae.
Abstract
Improved radii, masses and temperatures of the evolved early A-type binary β Aurigae are determined through an analysis of the available light and radial velocity curves. A new spectroscopic determination of the luminosity ratio is used to constrain the ratio of the radii, k=r_B_/r_A_, which is indeterminate from the photometric light curves; we find k=0.95+/-0.015. The resulting physical parameters of the two stars, accurate to ~1%, are: masses: M_A_=2.38Msun_, M_B_=2.31Msun_; radii: R_A_=2.77Rsun_, R_B_=2.63Rsun_; logg_A_=3.93, logg_B_=3.96; effective temperatures: T_A_=9350K, T_B_=9200K. β Aur has thus evolved into the upper part of the main-sequence band. Our measured rotational velocities of 33 and 34 km/s for the two components correspond exactly to synchronous rotation in the circular orbit. Comparison with new stellar evolution models gives a very good fit at an age of 5.710^8^yr and indicates that β Aur has a metal abundance that is close to solar or slightly below. β Aur is yet another system which is considerably younger than the Sun, but no richer in heavy elements. Recent optical interferometry of β Aur yields an accurate distance to the system (24.8+/-0.8pc) and allows an interesting cross-check of four different distance estimators. The result is a tighter constraint on the effective temperatures, rather than the masses and radii of the components.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1994
- Bibcode:
- 1994A&A...291..777N
- Keywords:
-
- A Stars;
- Eclipsing Binary Stars;
- Radii;
- Stellar Evolution;
- Stellar Mass;
- Stellar Models;
- Stellar Temperature;
- Chronology;
- Distance;
- Light Curve;
- Metallicity;
- Orbital Elements;
- Radial Velocity;
- Stellar Luminosity;
- Stellar Spectrophotometry;
- Astronomy;
- STARS: BINARIES;
- SPECTROSCOPIC;
- STARS: ECLIPSING;
- STARS: FUNDAMENTAL PARAMETERS;
- STARS: EVOLUTION;
- STARS: INDIVIDUAL: {BETA} AUR