Case a binary evolution

Conference item

We undertake a comparison of observed Algo-type binaries with a library of computed Case A binary evolution tracks. The library consists of 5500 binary tracks with various values of initial primary mass M-10, mass ratio q(0), and period P-0, designed to sample the phase-space of Case A binaries in the range -0.10 less than or equal to log M-10 < 1.7. Each binary is evolved using a standard code with the assumption that both total mass and orbital angular momentum are conserved. This code follows the evolution of both stars until the point where contact or reverse mass transfer occurs. The resulting binary tracks show a rich variety of behaviour which we sort into several subclasses of Case A and Case B. We present the results of this classification, the final mass ratio and the fraction of time spent in Roche Lobe overflow for each binary system. The conservative assumption under which we created this library is expected to hold for a broad range of binaries, where both components have spectra in the range GO to 131 and luminosity class III - V. We gather a list of relatively well-determined observed hot Algol-type binaries meeting this criterion, as well as a list of cooler Algol-type binaries where we expect significant dynamo-driven mass loss and angular momentum loss. We fit each observed binary to our library of tracks using a chi(2)-minimizing procedure. We find that the hot Algols display overall acceptable chi(2) confirming the conservative assumption, while the cool Algols show much less acceptable chi(2) suggesting the need for more free parameters, such as mass and angular momentum loss.

Authors: Nelson, C; Eggleton, P

• Publication status: Published
• Journal: EVOLUTION OF BINARY AND MULTIPLE STAR SYSTEMS
• Volume: 229
• Pages: 193-204
• Publication date: 2001-01-01
• Event title: Conference on Evolution of Binary and Multiple Star Systems
• ISBN: 1583810617
• Keywords: ABSOLUTE PARAMETERS; ALGOL BINARIES; SYSTEMS; SPECTROSCOPIC ORBIT; REDISCUSSION; ECLIPSING BINARIES; MAJORIS; CASSIOPEIAE; VARIABLE-STARS