Spectroscopic binaries with components of similar mass

Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK

Received: 1 June 2006
Accepted: 6 July 2006

Abstract

The assertion that there is an intrinsic excess of binaries with mass ratios – the twin hypothesis – is investigated. A strong version of this hypothesis (), due to Lucy & Ricco (1979, AJ, 84, 401) and Tokovinin (2000, A&A, 360, 997), refers to a narrow peak in the distribution function  for . A weak version (), due to Halbwachs et al. (2003, A&A, 397, 159), refers to a broad peak for . Current data on SB2's is analysed and is found to be statistically significant for a sample restricted to orbits of high precision. But claims that is significant for binaries with special characteristics are not confirmed since the sample sizes are well below the minimum required for a reliable test. With regard to , additional observational evidence is not presented, but evidence to the contrary in the form of Hogeveen's (1992, Ap&SS, 196, 299) model of biased sampling with is criticized. Specifically, his success in thus fitting catalogued data depends on implausible assumptions about the research methodologies of binary-star spectroscopists.