The binary system o Per: Orbital elements, component parameters, and helium abundance
Abstract
The radial velocities V_r of the components of the binary system o Per were measured from high-resolution, high signal-to-noise ratio CCD spectra. These data and all of the previously published V_r determinations were used to refine the orbital elements. The following effective temperatures and surface gravities were obtained: T_eff = 22,700 +/- 1500 K, log g = 3.4 +/- 0.2 for the primary component (star A) and T_eff = 21000 +/- 1500K, log g = 4.0 +/- 0.2 for the secondary component (star B). The rotational velocity was found from HeI and MgII lines to be v sin i = 89 +/- 4 km s^-1 for star A and v sin i = 87 +/- 3 km s^-1 for star B. The helium abundance derived from blue (lambda < 5000 A) HeI lines turned out to be enhanced in component A (He/H = 0.18 +/- 0.01) and nearly normal in component B (He/H = 0.11 +/- 0.01). The relative ages of the components, t_A/t_MS = 0.96 and t_B/t_MS = 0.54, which were estimated from evolutionary calculations, suggest that the primary is near completion of the main-sequence phase, while the secondary is only halfway through this phase. These data together with our previous results for binary early B stars lend support to the age dependence of the helium abundance. This dependence can be explained by mixing in the main-sequence phase. It is concluded that binarity strongly affects the mixing pattern.
- Publication:
-
Astronomy Reports
- Pub Date:
- September 1997
- Bibcode:
- 1997ARep...41..630L