The way to a double degenerate: ∼15-20 per cent of 1 M_⊙ ≤ M ≤ 8 M_⊙ stars have an M > 1 M_⊙ companion

Abstract

We find that ∼15-20 per cent of A-type stars or red giants are bound with a massive companion (M_secondary > 1 M_⊙) in an intermediate wide orbit (0.5 < P < 5000 yr). These massive binaries are expected to form wide-orbit, double-degenerate systems (WODDs) within ≲10 Gyr implying that ∼10 per cent of white dwarfs (WDs) are expected to be part of a WODD with a lighter WD companion. These findings are based on an analysis of previous adaptive optics observations of A-type stars and radial velocity measurements of red giants and shed light on the connection between multiplicity function of stars and detected double degenerates. We expect that Gaia will find ∼10 new WODDs within 20 pc from the sun. These results put a stringent constraint on the collision model of Type Ia supernovae in which triple stellar systems that include a WODD as the inner binary are required to be abundant.