A methodology for studying physical and dynamical properties of multiple stars. Application to the system of red dwarfs Gl 22

Abstract

Aims. The main aim of this study is the elaboration of a methodology for studying physical and dynamical properties of multiple stars and its application to the hierarchical triple system Gl 22. A careful evaluation of the components' masses and a study of the system's overall stability and long-term dynamical evolution were also pursued. Methods. New NIR speckle interferometric observations with the 6 m telescope of the Special Astrophysical Observatory (Russia) in the K photometric band have been carried out. We have made use of the method for orbit calculation reported by Docobo (1985).Results. An original methodology was elaborated and applied to evaluate the most probable elements of the outer orbit. Due to the almost definitive orbit of the inner pair, which just covered a full revolution, the motion of B relative to MC A has been carefully calculated. The position of MC A was estimated on the basis of differential photometry and empirical mass-luminosity relationships. A weak sinusoidal pattern in the apparent motion of the component B was noticed. Conclusions. Our methodology was successfully applied to the triple system Gl 22. The newly calculated outer orbit exhibits a moderate eccentricity (e = 0.29), which differs from the previously known circular solutions. Both orbits are coplanar and corevolving. This already known suggestion is now based on a much larger set of observational data, including a significant number of speckle measurements. Gl 22 is most likely a dynamically stable system, at least on the time scale of 10 Myr. The sinusoidal pattern in the motion of the B component could be caused by a fourth, unseen, very low-mass object with a mass of 0.015 M (16 M J ) on a circular orbit around B with a period of ∼15 yr and semimajor axis 0. 35.

Are the orbital poles of binary stars in the solar neighbourhood anisotropically distributed?

“…WDS 00321+6715Aa,Ab and AB. The preliminary visual orbits of this triple hierarchical system were computed by Docobo et al (2008). No radial velocity measurements are available to resolve the ambiguity of the ascending node.…”

“…A1918b : Aitken (1918); Abt2006: Abt & Willmarth (2006); AST1999: Franz et al (1999); AST2001: Benedict et al (2001); B1960c: van den Bos (1960); Bag2005: Balega et al (2005); Baz1980b: Baize (1980); Chg1972: Chang (1972); CIA2010: Farrington et al (2010); Cou1960b: Couteau (1960; Doc1985c: Docobo & Costa (1985); Doc2008d: Docobo et al (2008); Doc2010d: Docobo & Ling (2010); Dom1978: Dommanget (1978; Dru1995: Drummond et al (1995); Duq1991b: Duquennoy et al (1991 Egg1956: Eggen (1956; Egn2008: Eggenberger et al (2008); Fek1983: Fekel & Tomkin (1983 FMR2008b: Rica Romero (2008 Frv1999: Forveille et al (1999; Gri1975: Griffin & Emerson (1975); Gri1998: Griffin (1998) Acknowledgements. We dedicate this paper to the memory of J. Dommanget, who initiated this study and could unfortunately not see it accomplished.…”

Astrometric mass ratios of 248 long-period binary stars resolved in Hipparcos and Gaia EDR3

“…HIP 2552 = Gl 22 is an archetypical and well studied multiple system of late-type main sequence dwarfs, for which our much perturbed solution q = 4.3 betrays the fast orbital motion of the inner, unresolved components. A brief summary of the impressive observational history can be found in Docobo et al (2008). The preliminary orbit of the outer pair (AB in our catalog) obtained by Hershey (1973) from photographic measurements has been much improved over the decades and complemented with a tighter inner orbit of the Aa and Ab components, as per WDS designation (Söderhjelm 1999;Lampens & Strigachev 2001).…”

A first-order dynamical model of hierarchical triple stars and its application

“…For HIP 2552, there are 16 RPD points spanning from 1989 to 2005 of inner orbit, 75 points from 1923 to 2010 of the outer one, and 151 HIAD in reference to an acceleration solution with 7 parameters. The inner and outer orbits were provided by Docobo et al (2008) and are evaluated as good and indeterminate by ORB6. K-model is also firstly used to fit the observations.…”