Statistical errors and systematic biases in the calibration of the convective core overshooting with eclipsing binaries. A case study: TZ Fornacis

Abstract

We attempt to constrain the initial helium abundance, the age and the efficiency of the convective core overshooting of the binary system TZ Fornacis. Our main aim is in pointing out the biases in the results due to not accounting for some sources of uncertainty. We adopt the SCEPtER pipeline, relying on stellar models computed with two stellar evolutionary codes (FRANEC and MESA). We found multiple independent groups of solutions. The best one suggests a system of age 1.10 $\pm$ 0.07 Gyr (primary star in the central helium burning stage, secondary in the sub-giant branch), with a helium-to-metal enrichment ratio of $\Delta Y/\Delta Z=1$ and core overshooting parameter $\beta =0.15\pm 0.01$ (FRANEC) and $f_{\mathrm{ov}}=0.013\pm 0.001$ (MESA). The second class of solutions, characterised by a worse goodness-of-fit, still suggest a primary star in the central helium-burning stage but a secondary in the overall contraction phase, at the end of the main sequence. The FRANEC grid provides an age of $1.16_{-0.02}^{+0.03}$ Gyr and $\beta =0.25_{-0.01}^{+0.005}$, while the MESA grid gives $1.23\pm 0.03$ Gyr and $f_{\mathrm{ov}}=0.025\pm 0.003$. We also show that very precise mass determinations with uncertainty of a few thousandths of solar mass are required to obtain reliable determinations of stellar parameters, as mass errors larger than approximately 1% lead to estimates that are not only less precise but also biased. Moreover, we show that a fit obtained with a grid of models computed at a fixed $\Delta Y/\Delta Z$ can provide biased age and overshooting estimates. The possibility of independent overshooting efficiencies for the two stars of the system is also explored. This work confirms that to constrain the core overshooting parameter by means of binary systems is a very difficult task that requires an observational precision still rarely achieved and robust statistical methods.

arXiv commentA&A accepted. Abstract shortened

References in corpus (25)

• The chemical composition of the Sun
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Accurate masses and radii of normal stars: modern results and applications
• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• The Victoria-Regina Stellar Models: Evolutionary Tracks and Isochrones for a Wide Range in Mass and Metallicity that Allow for Empirically Constrained Amounts of Convective Core Overshooting
• The Pisa pre-main sequence tracks and isochrones. A database covering a wide range of Z, Y, mass, and age values
• Revised Primordial Helium Abundance Based on New Atomic Data
• Measuring the extent of convective cores in low-mass stars using Kepler data: towards a calibration of core overshooting
• The Pisa Stellar Evolution Data Base for low-mass stars
• DY/DZ from fine structure in the Main Sequence based on Hipparcos parallaxes
• The cosmic production of Helium
• ΔY/ ΔZ from the analysis of local K dwarfs
• Toward a consistent use of overshooting parametrizations in 1D stellar evolution codes
• Confronting uncertainties in stellar physics: calibrating convective overshooting with eclipsing binaries
• Uncertainties in grid-based estimates of stellar mass and radius. SCEPtER: Stellar CharactEristics Pisa Estimation gRid
• Asymptotic Giant Branch predictions: theoretical uncertainties
• Confronting uncertainties in stellar physics II. exploring differences in main-sequence stellar evolution tracks
• The Araucaria Project: High-precision orbital parallax and masses of the eclipsing binary TZ~Fornacis
• Calibrating convective-core overshooting with eclipsing binary systems. The case of low-mass main-sequence stars
• Absolute parameters for AI Phoenicis using WASP photometry
• On the age of Galactic bulge microlensed dwarf and subgiant stars
• Grid-based estimates of stellar ages in binary systems. SCEPtER: Stellar CharactEristics Pisa Estimation gRid
• A statistical test on the reliability of the non-coevality of stars in binary systems

Cited by in corpus (32)

• The dependence of convective core overshooting on stellar mass: Additional binary systems and improved calibration
• The dependence of convective core overshooting on stellar mass: semi-empirical determination using the diffusive approach with two different element mixtures
• The mass discrepancy in intermediate- and high-mass eclipsing binaries: the need for higher convective core masses
• Mixing by overshooting and rotation in intermediate mass stars
• The dependence of convective core overshooting on stellar mass: reality check, and additional evidence
• The Gaia-ESO Survey: open clusters in Gaia-DR1 - a way forward to stellar age calibration
• When the tale comes true: multiple populations and wide binaries in the Orion Nebula Cluster
• The treatment of mixing in core helium burning models -- III. Suppressing core breathing pulses with a new constraint on overshoot
• Convective boundary mixing in main-sequence stars: theory and empirical constraints
• Evolutionary modelling of subdwarf B stars using MESA with the predictive mixing and convective premixing schemes
• Fundamental properties of red-clump stars from long-baseline H-band interferometry
• The Araucaria Project: High-precision orbital parallax and masses of eclipsing binaries from infrared interferometry
• Tango of celestial dancers: A sample of detached eclipsing binary systems containing g-mode pulsating components. A case study of KIC9850387
• Overshooting calibration and age determination from evolved binary system
• The Araucaria project: High-precision orbital parallaxes and masses of binary stars. I. VLTI/GRAVITY observations of ten double-lined spectroscopic binaries
• Examining the Relationship Between Convective Core Overshoot and Stellar Properties Using Asteroseismology
• Discovery and characterisation of long-period eclipsing binary stars from Kepler K2 campaigns 1, 2 and 3
• The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18
• Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. I. NGC 6940
• Modelling of the B-type binaries CW Cep and U Oph: A critical view on dynamical masses, core boundary mixing, and core mass
• Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- XII. A sample of systems with $K2$ photometry
• Impact of measurement errors on the inferred stellar asteroseismic ages. Statistical models for intermediate age main sequence and red giant branch stars
• Asteroseismic age estimates of RGB stars in open clusters. A statistical investigation of different estimation methods
• Surface brightness-colour relations of dwarf stars from detached eclipsing binaries -- I. Calibrating sample
• Relevance of the small frequency separation for asteroseismic stellar age, mass, and radius. A statistical investigation for main-sequence low-mass stars
• Stellar model calibrations with the Ai Phe binary system. Open questions about the robustness of the fit
• WASP 0639-32: a new F-type subgiant/K-type main-sequence detached eclipsing binary from the WASP project
• Age and convective core overshooting calibrations in CPD-54 810 binary system. Statistical investigation on the solution robustness
• Theoretical investigation on the mass loss impact on asteroseismic grid-based estimates of mass, radius, and age for RGB stars
• Constraining the helium-to-metal enrichment ratio $\Delta Y/\Delta Z$ from main sequence binary stars. Theoretical analysis of the accuracy and precision of the age and helium abundance estimates
• Mixing-length calibration from field stars. An investigation on statistical errors, systematic biases, and spurious metallicity trends
• One size does not fit all: Evidence for a range of mixing efficiencies in stellar evolution calculations