Comparative statistics and origin of triple and quadruple stars

By A. Tokovinin. 2008

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The statistics of catalogued quadruple stars consisting of two binaries (hierarchy 2 + 2), is studied in comparison with triple stars, with respective sample sizes of 81 and 724. Seven representative quadruple systems are discussed in greater detail. The main conclusions are as follows. (i) Quadruple systems of e Lyr type with similar masses and inner periods are common, in 42 per cent of the sample the outer mass ratio is above 0.5 and the inner periods differ by less than 10 times. (ii) The distributions of the inner periods in triple and quadruple stars are similar and bimodal. The inner mass ratios do not correlate with the inner periods. (iii) The statistics of outer periods and mass ratios in triples and quadruples are different. The median outer mass ratio in triples is 0.39 independently of the outer period, which has a smooth distribution. In contrast, the outer periods of 25 per cent quadruples concentrate in the narrow range from 10 to 100 yr, the outer mass ratios of these tight quadruples are above 0.6 and their two inner periods are similar to each other. (iv) The outer and inner mass ratios in triple and quadruple stars are not mutually correlated. In 13 per cent of quadruples both inner mass ratios are above 0.85 (double twins). (v) The inner and outer orbital angular momenta and periods in triple and quadruple systems with inner periods above 30 d show some correlation, the ratio of outer-to-inner periods is mostly comprised between 5 and 10 4 . In the systems with small period ratios the directions of the orbital spins are correlated, while in the systems with large ratios they are not. The properties of multiple stars do not correspond to the products of dynamical decay of small clusters, hence the N-body dynamics is not the dominant process of their formation. On the other hand, rotationally driven (cascade) fragmentation possibly followed by migration of inner and/or outer orbits to shorter periods is a promising scenario to explain the origin of triple and quadruple stars.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e450c779301b652977d3fd0d2206e8f11f784932

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Citations in the corpus

The VAST Survey - III. The multiplicity of A-type stars within 75 pc (2013, background): “Of the eight known quadruple systems, three are ofǫ Lyr-type, consisting of two pairs of binaries, with similar mass ratios and orbital periods, in a wide orbit (Tokovinin 2008).”
SPECTROSCOPIC ORBITS FOR 15 LATE-TYPE STARS (2016, background): “…the mass of the invisible Ab component by assuming that the orbital angular momenta of the inner and outer orbits are aligned, but the study by Tokovinin (2008) concludes that the correlation is stronger when the ratio of the outer to inner orbits, P PL S, is close to 5, the dynamical…”
FROM BINARIES TO MULTIPLES. II. HIERARCHICAL MULTIPLICITY OF F AND G DWARFS (2014, background): “Tokovinin (2008) noted that in 2+2 quadruples with PL 10 5.4 d both inner binaries have similar total masses and periods.”
The Eccentric Kozai-Lidov Effect and Its Applications (2016, methodology): “Tokovinin 2008 0.1 1 10 100 0 50 100 150 180 P in,F [days] F in a l o b liq u it y [ d e g ] 0 0.2 0.4 0.6 0.8 Obs.”
Unique sextuple system: 65 Ursae Majoris (2012, background): “Nevertheless, 65 UMa is a rather unusual system, we presently know of only 11 other sextuple systems (see Eggleton & Tokovinin 2008).”
Stellar Multiplicity (2013, methodology): “For instance, all 11 sextuple systems in the Multiple Star Catalog are A-type stars (Eggleton & Tokovinin 2008), while a single such candidate system is known among nearby solar-type stars (Raghavan et al. 2010), and the highest-order multiple system containing only low-mass stars currently known…”
Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation (2008, background): “For stellar triple and quadruple systems, Tokovinin (2008) re- c© 0000 RAS, MNRAS 000, 000–000 ports that triples are observed to have a median mass ratio of 0.39 independent of the outer orbital period while quadruples involving two binary sub-components have a similar median mass ratio of ≈ 0.45,…”
A comprehensive study of the Kepler triples via eclipse timing (2015, background): “…d/c3; c: Cubic ephemeris – c3 = 2.57(6)× 10−12 d/c3; d: Cubic ephemeris – c3 = −0.058(2)× 10−12 d/c3 1991), or even a form with a peak near ∼3 000 years which was obtained both from observations (Tokovinin 2008) and numerical simulations (Naoz & Fabrycky 2014) of triples containing close binaries.”
Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius (2009, unknown): “While the probability that there is a background star closerthan Tokovinin (2008) shows that at least 8% of the solar-type stars have three or more components.”
CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS (2015, background): “Afterwards, its membership in the very wide system has been investigated by Poveda et al. (1994), Tokovinin (2008), and Dhital et al. (2010), for example, and confirmed and quantified by Caballero (2009).”