Multiplicity statistics and properties across the HR diagram
Abstract
It is well established that the main-sequence binary fraction increases with primary mass, but we have only recently explored in detail other important parameters such as age, metallicity, and environment. In this proceeding, I overview recent observations that demonstrate the close binary fraction (a ≲ 10 AU) of solar-type stars decreases with metallicity but is relatively constant with respect to age or environmental density, while the wide binary fraction (a gtrsim 1,000 AU) is metallicity invariant but decreases dramatically during the pre-main-sequence phase. Wider binaries are intrinsically weighted toward smaller mass ratios, a trend that is especially evident for companions to massive OB primaries. I also discuss the properties of white dwarfs in binaries and the statistics of triples and higher-ordered multiples. I explain the various correlations with respect to mass and orbital separation in the context of protobinary fragmentation, accretion, and migration.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- 2019
- Bibcode:
- 2019MmSAI..90..347M