New sample of low mass ratio contact binary systems

We provide empirical insights into their definition, structure, rotational stability, and parameter relations. We first examined the range of mass ratios that characterize these systems, and based on an analysis of 818 contact binaries, we established an empirical threshold of q~0.27 to identify systems with a low mass ratio.

To investigate the rotational stability, we conducted a Monte Carlo analysis of the squared gyration radii (k1^2^ and k2^2^) and assessed the resulting spin-to-orbital angular momentum ratio (Jspin/Jorb). While k1 remains nearly constant, k2 and Jspin/Jorb decrease slightly with increasing mass ratio. This emphasizes the role of the secondary star's internal structure.