Period ratios and observation of noticeable resonance at 3:2 for 2+2 quadruple systems

ABSTRACT Quadruple stellar systems with two mutually orbiting eclipsing pairs (2+2 quadruples) are currently of great scientific interest because they offer a unique opportunity to determine the physical parameters of their constituent stars with high precision. In this study, we enlarge their numbers and present an analysis of the orbital periods and their ratios for a sample of 781 quadruple candidates with a 2+2 structure. Moreover, we compare the observed distribution of period ratios to a simulated prediction based on a uniform distribution of inner periods. We find a preference for a 3:2 resonance between the inner orbital periods, while the 1:1, 4:3, and 5:3 resonances do not deviate significantly from the predicted distribution model. Higher resonant values are on a slight decline, probably due to a lack of data. These results, derived from the largest statistical ensemble of 2+2 quadruples to date, provide evidence for the hypothesis that gravitational interactions between the star pairs can preferentially lead to a 3:2 resonance during their evolution.