A comparison between observed Algol-type double stars in the Solar neighborhood and evolutionary computations of galactic case A binaries with a B-type primary at birth

TL;DR

This paper compares observed Algol-type binaries with evolutionary models of galactic case A binaries, revealing insights into mass transfer, contact evolution, and angular momentum loss.

Contribution

It introduces detailed evolutionary calculations of close binaries with B-type primaries and assesses contact models against observations, constraining contact star physics.

Findings

Mass transfer in Algols is likely non-conservative.

Contact during evolution does not always cause mergers.

Angular momentum loss is moderate during binary evolution.

Abstract

We first discuss a large set of evolutionary calculations of close binaries with a B-type primary at birth and with a period such that the Roche lobe overflow starts during the core hydrogen burning phase of the primary (intermediate mass and massive case A binaries). The evolution of both components is followed simultaneously allowing us to check for the occurrence of contact binaries. We consider various models to treat a contact system and the influence of these models on the predicted Algol-type system population is investigated. We critically discuss the available observations of Algol-type binaries with a B-type primary at birth. Comparing these observations with the predictions allows us to put constraints on the contact star physics. We find that mass transfer in Algols is most probably not conservative, that contact during this phase does not necessarily lead to a merger, and that angular momentum loss must be moderate.