Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- II. Two spotted M < 1 M$_\odot$ systems at different evolutionary stages

TL;DR

This study provides detailed spectroscopic and photometric analysis of two low-mass eclipsing binaries at different evolutionary stages, revealing their physical parameters, activity levels, and evolutionary status, with implications for stellar models.

Contribution

It presents the first detailed analysis of two previously unknown <1 M_sun detached eclipsing binaries, including their physical parameters and evolutionary states, using combined spectroscopic and photometric data.

Findings

ASAS J045304-0700.4 is an old, metal-poor, active system at the end of the Main Sequence.

ASAS J082552-1622.8 is a metal-rich, active binary with near-equal component radii.

Both systems exhibit significant out-of-eclipse variations likely due to large cold spots.

Abstract

Aims. We present the results of our detailed spectroscopic and photometric analysis of two previously unknown < 1 M{_\sun} 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 = 0.8452 \pm 0.0056 M$_\odot$, M2 = 0.8390 \pm 0.0056 M$_\odot$ and radii of R1 = 0.848 \pm 0.005 R$_\odot$ and R2 = 0.833 \pm 0.005 R$_\odot$, 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 = 0.703 \pm 0.003 M$_\odot$, M2 = 0.687 \pm 0.003 M$_\odot$ and radii of R1 = 0.694(+0.007-0.011) R$_\odot$ and R2 = 0.699(+0.011-0.014) R$_\odot$. 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.