An analysis of the TZ Fornacis binary system

Abstract

Context. TZ Fornacis (TZ For) is an evolved detached binary system that is difficult to model and interpret, but very useful for testing stellar evolution theory and physics. Aims. We aim to search for solutions that are self-consistent and to determine the necessary stellar physics input. We also check solutions found previously for their internal consistency and for reproducibility. Methods. We use both a single and a binary stellar evolution code, and take into account all known system properties. We determine the physical stellar parameters by imposing that the models match the known radii for identical stellar ages. The evolution has to be consistent with a binary system in classical Roche geometry. Results. We obtained two different solutions to model TZ For successfully. Both depend on avoiding a long evolution on the first giant branch and imply a sufficiently large convective core on the main sequence. TZ For can be modelled consistently as a detached binary system by invoking either a substantial amount of core overshooting or a tidally enhanced wind mass loss along the red giant branch. An evolution with Roche-lobe overflow can definitely be excluded. Conclusions. A comparison of our results with previous studies also reveals that in addition to uncertainties associated with the input physics, the modelling of overshooting by different algorithms can have a strong impact.

The Araucaria project: High-precision orbital parallax and masses of eclipsing binaries from infrared interferometry

“…With high-precision measurements, evo-Article number, page 1 of 22 arXiv:1910.03393v1 [astro-ph.SR] 8 Oct 2019 A&A proofs: manuscript no. 2019-Eclipsing-v2r2 lutionary models can be tightly constrained and provide a better understanding of the stellar interior physics (Higl et al 2018;Claret & Torres 2018;Valle et al 2017).…”

Mixing by overshooting and rotation in intermediate-mass stars

“…The observed value is V sin i (TZF 2 ) = 46 km s −1 implying an inclination angle i ∼ 60 • . Thus, also the secondary star of TZ Fornacis provides direct independent evidence that the initial rotation rate of the secondary component was not negligible (see also Higl et al 2018), even if not as high as that of α Aur 2 .…”

“…Different approaches are used to constrain the d ov parameter, using various types of data, such as: color-magnitude diagrams of star clusters (e.g. Woo et al 2003;Rosenfield et al 2017), bump Cepheids (Keller & Wood 2006), asteroseismology of either OB (Moravveji et al 2015) or red clump (Bossini et al 2017) stars, or detached double-lined eclipsing binaries (DLEBs; Stancliffe et al 2015;Claret & Torres 2016;Valle et al 2016;Claret & Torres 2017;Valle et al 2017;Higl & Weiss 2017;Claret & Torres 2018;Higl et al 2018;Constantino & Baraffe 2018). A series of works (e.g.…”

Space-Based Photometry of Binary Stars: From Voyager to TESS

“…They can therefore be used to check and calibrate theoretical models of stellar structure and evolution, as the models can be confronted with two stars which have different masses, radii and T eff s (all measured to 1% or better) but the same age and chemical composition. Past work has considered phenomena such as the primordial helium abundance [11,12], the helium-to-metals enrichment ratio [13], the strength of convective core overshooting and its dependence on stellar mass [14][15][16], the mixing length parameter α MLT [17], and mass loss by stellar winds [18]. EBs have also been used to establish empirical mass-radius-T eff -luminosity relations [9,19,20] which are useful in particular for measuring the properties of extrasolar planets [21,22].…”