We show how the second sequence seen lying above the main sequence in cluster colour magnitude diagrams results from binaries with a large range of mass ratios and not just from those with equal masses. We conclude that the presence of a densely populated second sequence, with only sparse filling in between it and the single star main sequence, does not necessarily imply that binary mass ratios are close to unity.
Cite
@article{arxiv.astro-ph/9807108,
title = {The Binary Second Sequence in Cluster Colour--Magnitude Diagrams},
author = {Jarrod Hurley and Christopher A. Tout},
journal= {arXiv preprint arXiv:astro-ph/9807108},
year = {2015}
}