Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - IV. A 0.61 + 0.45 M⊙ binary in a multiple system

We present the orbital and physical parameters of a newly discovered low-mass detached eclipsing binary from the All-Sky Automated Survey (ASAS) data base: ASAS J011328-3821.1 A, which is a member of a visual binary system with the secondary component separated by about 1.4 arcsec. The radial velocities have been calculated from the high-resolution spectra obtained with the 1.9-m Radcliffe telescope/Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) spectrograph, the 3.9-m Anglo-Australian Telescope (AAT)/University College London Echelle Spectrograph (UCLES) and the 3.0-m Shane telescope/Hamilton Spectrograph (HamSpec) on the basis of the TODCOR technique and the positions of the H_α emission lines. For the analysis, we have used V- and I-band photometry obtained with the 1.0-m Elizabeth telescope and the 0.41-m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT), supplemented with the publicly available ASAS light curve of the system.

We have found that ASAS J011328-3821.1 A is composed of two late-type dwarfs, which have masses of M₁ = 0.612 ± 0.030 M_⊙ and M₂ = 0.445 ± 0.019 M_⊙ and radii of R₁ = 0.596 ± 0.020 R_⊙ and R₂ = 0.445 ± 0.024 R_⊙. Both show a substantial level of activity, which manifests in strong H_α and H_β emission and the presence of cool spots. The influence of the third light on the eclipsing pair properties has also been evaluated and the photometric properties of component B have been derived. A comparison with several popular stellar evolution models shows that the system is on its main-sequence evolution stage and that it is probably more metal-rich than the Sun. We have also found several clues to suggest that component B itself is a binary composed of two nearly identical ∼0.5-M_⊙ stars.