A young spectroscopic binary in a quintuple system part of the Local Association

Abstract

Context. Double-lined spectroscopic (SB2) binaries allow us to obtain a direct determination of the masses of their components, which is essential to test stellar models. Although these objects only provide a lower limit for the mass, they are more abundant than their eclipsing counterparts as they are not as strongly limited by the inclination of their orbit. Aims. Our aim is to derive the orbital and physical parameters of GJ 1284, a young SB2. We also revise the membership of this system and its two wide co-moving companions, GJ 898 and GJ 897AB, to a young moving group to assess, along with other youth indicators, their age. Afterwards, we compare the results from these analyses and the photometry of these systems with several pre-main-sequence evolutionary models. Methods. We use high-resolution spectra to determine the radial velocity of each component of GJ 1284 and the orbit of the system alongside its systemic velocity. Additionally, we use TESS photometry to derive the rotational period of the GJ 1284 and its two wide companions. Results. GJ 1284 is a binary system located at approximately 16 pc with an eccentric orbit (e = 0.505) of 11.83 d period made up of an M2–M2.5 + M3–M3.5 with minimum masses of M sin 3i = 0.141 ± 0.003 and 0.1189 ± 0.003 M⊙, respectively. The revised systemic velocity of γ = 0.84 ± 0.14 km s−1 suggests that it is a member of the Local Association. The kinematics together with other activity and youth indicators imply an age of 110–800 Myr for this system and its two companions. Conclusions. The isochronal ages derived from the comparison of the photometry with several evolutionary models are younger than the age estimated from the activity indicators for the three co-moving systems. The masses for the components of GJ 1284, derived from their luminosity and age using the different models, are not consistent with the masses derived from the photometry, except for the PARSEC models, but are compatible with dynamical masses of double-lined eclipsing binaries with similar ages and spectral types. The effect of magnetic activity in the form of spots can reconcile to some extent the photometric and dynamical masses, but is not considered in most of the evolutionary models.