The compact multiple system HIP 41431

Abstract

The nearby (50 pc) K7V dwarf HIP 41431 (EPIC 212096658) is a compact 3tier 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. • 16±0. • 11, while the outer orbit is inclined to their common plane by 21 • ±16 • . 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.

The compact triply eclipsing triple star TIC 209409435 discovered with TESS

“…Turning back to the most prominent characteristic of our triple, i.e. its flatness, other similarly very flat (im < 5 • ) and compact (P2 < 200 d) triple systems with accurately known parameters that were reported previously are HD 181068 (Borkovits et al 2013), HD 144548 (Alonso et al 2015), ξ Tau (Nemravová et al 2016), EPIC 249432662 (Borkovits et al 2019a), HIP 41431 (Borkovits et al 2019b) and TIC 220397947 (Borkovits et al 2020). 6 All of these systems show remarkable similarities, as one can see in Table 5.…”

TIC 278956474: Two Close Binaries in One Young Quadruple System Identified by TESS

“…For our analysis we used software package Lightcurvefactory (Borkovits et al 2018(Borkovits et al , 2019a. This package is able to model the light-ETV and RV curves of any configurations of eclipsing systems formed by 2-4 stars (i.e.…”

“…Software: BiSEPS (Willems & Kolb 2002, 2004Willems et al 2006;Davis et al 2010;Farmer et al 2013), gnuplot (http://www.gnuplot.info/), Lightcurvefactory (Borkovits et al 2018(Borkovits et al , 2019a, MESA (Paxton et al 2011(Paxton et al , 2013(Paxton et al , 2015, PARSEC (Bressan et al 2012), Wōtan (Hippke et al 2019).…”

Close binaries in hierarchical stellar systems

“…Their orbits are approximately aligned, period ratios are moderate (on the order of 20), and the orbits have small eccentricities. A good example is HIP 41431, a compact quadruple system of K7V dwarfs with periods of 2. d 9, 59 d, and 3.9 yr (Borkovits et al, 2019).…”