The nearby ( 50 pc ) K7V dwarf HIP 41431 ( EPIC 212096658 ) is a compact 3-tier hierarchy .
Three K7V stars with similar masses , from 0.61 to 0.63 solar , make a triple-lined spectroscopic system where the inner binary with a period of 2.9 days is eclipsing , and the outer companion on a 59-day orbit exerts strong dynamical influence revealed by the eclipse time variation in the Kepler photometry .
Moreover , the centre-of-mass of the triple system moves on a 3.9-year orbit , modulating the proper motion .
The mass of the 4-th star is 0.35 solar .
The Kepler and ground-based photometry and radial velocities from four different spectrographs are used to adjust the spectro-photodynamical model that accounts for dynamical interaction .
The mutual inclination between the two inner orbits is 2 \fdg 16 \pm 0 \fdg 11 , while the outer orbit is inclined to their common plane by 21 \degr \pm 16 \degr .
The inner orbit precesses under the influence of both outer orbits , causing observable variation of the eclipse depth .
Moreover , the phase of the inner binary is strongly modulated with a 59-day period and its line of apsides precesses .
The middle orbit with eccentricity e = 0.28 also precesses , causing the observed variation of its radial velocity curve .
Masses and other parameters of stars in this unique hierarchy are determined .
This system is dynamically stable and likely old .