Highprecision elements of doublelined spectroscopic binaries from combined interferometry and spectroscopy. Application to the β Cephei star β Centauri
Abstract
Aims.We present methodology to derive highprecision estimates of the fundamental parameters of doublelined spectroscopic binaries. We apply the methods to the case study of the doublelined β Cephei star β Centauri. We also present a detailed analysis of β Centauri's lineprofile variations caused by its oscillations.
Methods: .Highresolution spectral time series and visual or interferometric data with a good phase distribution along the orbital period are required. We point out that a systematic error in the orbital amplitudes, and any quantities derived from them, occurs if the radial velocities of blended component lines are computed without spectral disentangling. This technique is an essential ingredient in the derivation of the physical parameters if the goal is to obtain a precision of only a few percent. We have devised iteration schemes to obtain the orbital elements for systems whose lines are blended throughout the orbital cycle.
Results: .We derive the component masses and dynamical parallax of β Centauri with a precision of 6% and 4%, respectively. Modelling allowed us to refine the mass estimates to 1% precision resulting in M_1=10.7± 0.1 M_☉ and M_2=10.3± 0.1 M_☉, and to derive the age of the system as being (14.1± 0.6)× 10^{6} years. We deduce two oscillation frequencies for the broadlined primary of β Centauri: f_1=7.415 c d^{1} and f_2=4.542 c d^{1} or one of their aliases. The degrees of these oscillation modes are higher than 2 for both frequencies, irrespective of the alias problem. No evidence of oscillations in the narrowlined secondary was found.
Conclusions: .We propose that our iteration schemes be used in any future derivations of the spectroscopic orbital parameters of doublelined binaries with blended component lines to which disentangling can be successfully applied. The combination of parameters resulting from the iteration schemes with highprecision estimates of the orbital inclination and the angular semimajor axis from interferometric or visual measurements allows a complete solution of the system.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 August 2006
 DOI:
 10.1051/00046361:20064829
 arXiv:
 arXiv:astroph/0605220
 Bibcode:
 2006A&A...455..259A
 Keywords:

 stars: binaries: spectroscopic;
 stars: individual: β Centauri;
 methods: observational;
 methods: data analysis;
 line: profiles;
 techniques: spectroscopic;
 Astrophysics
 EPrint:
 12 pages, 13 figures, accepted for publication in A&