VW LMi: tightest quadruple system known. Light-time effect and possible secular changes of orbits

TL;DR

This study characterizes VW LMi, the tightest known quadruple star system, through new observations and analysis, revealing detailed orbital parameters, component masses, and dynamical interactions, including apsidal motion and orbital coplanarity.

Contribution

It provides the first comprehensive orbital and physical parameters of VW LMi, including new radial velocities, minima timings, and insights into its dynamical stability and configuration.

Findings

Total system mass estimated at 4.56 solar masses.

Detached binary exhibits apsidal motion with an 80-year period.

Mutual orbit is nearly coplanar, preventing inclination changes.

Abstract

Tightest known quadruple systems VW LMi consists of contact eclipsing binary with P_12 = 0.477551 days and detached binary with P_34 = 7.93063 days revolving in rather tight, 355.0-days orbit. This paper presents new photometric and spectroscopic observations yielding 69 times of minima and 36 disentangled radial velocities for the component stars. All available radial velocities and minima times are combined to better characterize the orbits and to derive absolute parameters of components. The total mass of the quadruple system was estimated at 4.56 M_sun. The detached, non-eclipsing binary with orbital period P = 7.93 days is found to show apsidal motion with U approximately 80 years. Precession period in this binary, caused by the gravitational perturbation of the contact binary, is estimated to be about 120 years. The wide mutual orbit and orbit of the non-eclipsing pair are found to be close to coplanarity, preventing any changes of the inclination angle of the non-eclipsing orbit and excluding occurrence of the second system of eclipses in future. Possibilities of astrometric solution and direct resolving of the wide, mutual orbit are discussed. Nearby star, HD95606, was found to form loose binary with quadruple system VW LMi.