English

Are the majority of Sun-like stars single?

Solar and Stellar Astrophysics 2015-06-23 v1

Abstract

It has recently been suggested that, in the field,  ⁣ ⁣56%\sim\!\!56\% of Sun-like stars (0.8MM1.2M0.8\,{\rm M}_{_\odot}\lesssim M_\star\lesssim 1.2\,{\rm M}_{_\odot}) are single. We argue here that this suggestion may be incorrect, since it appears to be based on the multiplicity frequency of systems with Sun-like primaries, and therefore takes no account of Sun-like stars that are secondary (or higher-order) components in multiple systems. When these components are included in the reckoning, it seems likely that only  ⁣46%\sim\!46\% of Sun-like stars are single. This estimate is based on a model in which the system mass function has the form proposed by Chabrier, with a power-law Salpeter extension to high masses; there is a flat distribution of mass ratios; and the probability that a system of mass MM is a binary is 0.50+0.46log10 ⁣(M/M)\,0.50 + 0.46\log_{_{10}}\!\left(M/{\rm M}_{_\odot}\right)\, for 0.08MM12.5M\,0.08\,{\rm M}_{_\odot}\leq M\leq 12.5\,{\rm M}_{_\odot}, 0\,0\, for M<0.08M\,M<0.08\,{\rm M}_{_\odot}, and 1\,1\, for M>12.5M\,M>12.5\,{\rm M}_{_\odot}. The constants in this last relation are chosen so that the model also reproduces the observed variation of multiplicity frequency with primary mass. However, the more qualitative conclusion, that a minority of Sun-like stars are single, holds up for virtually all reasonable values of the model parameters. Parenthetically, it is still likely that the majority of {\it all} stars in the field are single, but that is because most M Dwarfs probably are single.

Keywords

Cite

@article{arxiv.1502.04018,
  title  = {Are the majority of Sun-like stars single?},
  author = {A. P. Whitworth and O. Lomax},
  journal= {arXiv preprint arXiv:1502.04018},
  year   = {2015}
}

Comments

6 pages. Accepted by MNRAS