A New Look at the Binary Characteristics of Massive Stars

Content Provider	Semantic Scholar
Author	Kobulnicky, Henry A. Fryer, Chris L.
Copyright Year	2007
Abstract	We constrain the properties of massive binaries by comparing radial velocity data on 114 early-type stars in the Cygnus OB2 Association with the expectations of Monte Carlo models. Our comparisons test several popular prescriptions for massive binary parameters while highlighting the sensitivity of the best-fitting solutions to the adopted boundary conditions. We explore a range of true binary fraction, F , a range of power-law slopes, α, describing the distribution of companion masses between the limits q low and 1, and a range of power-law slopes, β, describing the distribution of orbital separations between the limits r in and r out. We also consider distributions of secondary masses described by a Miller-Scalo type initial mass function (IMF) and by a two-component IMF that includes a substantial " twin " population with M 2 ≃ M 1. Several seemingly disparate prescriptions for massive binary characteristics can be reconciled by adopting carefully chosen values for F , r in , and r out. We show that binary fractions F < 0.7 are less probable than F ≥ 0.8 for reasonable choices of r in and r out. Thus, the true binary fraction is high. For F = 1.0 and a distribution of orbital separations near the canonicaï Opik's Law distribution (i.e., flat; β = 0), the power law slope of the mass ratio distribution is α =-0.6 – 0.0. For F ≃ 0.8, α is somewhat larger, in the range-0.4 – 1.0. In any case, the secondary star mass function is inconsistent with a Miller-Scalo-like IMF unless the lower end is truncated below ∼2–4 M ⊙. In other words, massive stars preferentially have massive companions. – 2 – The best fitting models are described by a Salpeter or Miller-Scalo IMF for 60% of secondary star masses with the other ∼ 40% of secondaries having M 2 ≃ M 1 , i.e., " twins ". These best-fitting model parameters simultaneously predict the fraction of type Ib/c supernovae to be 30–40% of all core-collapse supernovae, in agreement with recent observational estimates.
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://arxiv.org/pdf/astro-ph/0605069v2.pdf
Language	English
Access Restriction	Open
Subject Keyword	Bethe–Salpeter equation Binary number CygnusEd Professional Entity Name Part Qualifier - adopted Estimated GUCY2C protein, human Large Molecular orbital Monte Carlo method Neoplasm Metastasis Probability Radial (radio) Solutions Stars, Celestial Stellar classification Velocity (software development) slope
Content Type	Text
Resource Type	Article