Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue. II. Two spotted M < 1 M_⊙ systems at different evolutionary stages

Aims: We present the results of our detailed spectroscopic and photometric analysis of two previously unknown <1 M_⊙ detached eclipsing binaries: ASAS J045304-0700.4 and ASAS J082552-1622.8.
Methods: With the HIgh Resolution Echelle Spectrometer (HIRES) on the Keck-I telescope, we obtained spectra of both objects covering large fractions of orbits of the systems. We also obtained V and I band photometry with the 1.0-m Elizabeth telescope of the South African Astronomical Observatory (SAAO). The orbital and physical parameters of the systems were derived with the PHOEBE and JKTEBOP codes. We investigated the evolutionary status of both binaries with several sets of widely-used isochrones.
Results: Our modelling indicates that (1) ASAS J045304-0700.4 is an old, metal-poor, active system with component masses of M₁ = 0.8338 ± 0.0036 M_⊙, M₂ = 0.8280 ± 0.0040 M_⊙ and radii of R₁ = 0.848 ± 0.005 R_⊙ and R₂ = 0.833 ± 0.005 R_⊙, which places it at the end of the Main Sequence evolution - a stage rarely observed for this type of stars. (2) ASAS J082552-1622.8 is a metal-rich, active binary with component masses of M₁ = 0.7029 ± 0.0045 M_⊙, M₂ = 0.6872 ± 0.0049 M_⊙ and radii of R₁ = 0.694^+0.007_-0.011 R_⊙ and R₂ = 0.699^+0.011_-0.014 R_⊙. Both systems show significant out-of-eclipse variations, probably owing to large, cold spots. We also investigated the influence of a third light in the second system.

Light curves are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/526/A29