Implications of a turbulent convection model for classical Cepheids

Abstract

The appearance of blue loops in the evolutionary tracks of intermediate-mass core He-burning stars is essential for explaining the observed characteristics of Cepheids. The blue loops for lower mass Cepheids cannot always be reproduced when only classical, local mixing length theory (MLT) is used. Additionally, classical models result in a mass discrepancy compared to pulsational and dynamical mass determinations. Both problems can be resolved through an ad-hoc extension of the MLT for convection. We use the non-local Kuhfuss turbulent convection model (TCM) which can explain overshooting directly from the solution of the TCM equations. The primary objective of this study is to test the predictions of the Kuhfuss TCM when applied to intermediate-mass core He-burning stars and validate the model predictions against observations of Cepheids. We used the state-of-the-art 1D stellar evolution code GARSTEC with the implementation of the Kuhfuss TCM and computed evolutionary tracks for intermediate-mass core He-burning stars. We compare these tracks with those computed with MLT including and excluding ad-hoc overshooting and with observations of five Cepheids in detached binary systems obtained from the literature. The stellar evolution tracks generated using the Kuhfuss TCM and MLT with ad-hoc overshooting exhibit similar appearances. Overshoot mixing from the convective boundaries and the occurrence of the Cepheid blue-loop have been achieved naturally as solutions to the Kuhfuss TCM equations. Furthermore, these models successfully reproduce observed stellar parameters including mass, luminosity, radius, and effective temperature. In conclusion, our TCM approach reproduces Cepheid blue loops and agrees with observations similarly well as MLT models with overshooting, however, without fine-tuning the model parameters or ad-hoc assumptions.

Accepted to A&A. 19 pages, 15 figures, 9 tables

References in corpus (32)

• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Low Temperature Opacities
• Intermediate-mass star models with different helium and metal contents
• Accurate dynamical mass determination of a classical Cepheid in an eclipsing binary system
• Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227
• On using the CMD morphology of M67 to test solar abundances
• On the effect of rotation on populations of classical Cepheids I. Predictions at solar metallicity
• New PARSEC database of alpha-enhanced stellar evolutionary tracks and isochrones I. Calibration with 47 Tuc (NGC104) and the improvement on RGB bump
• Cepheid Mass-loss and the Pulsation -- Evolutionary Mass Discrepancy
• The Cepheid mass discrepancy and pulsation-driven mass loss
• On the evolutionary and pulsation mass of Classical Cepheids: III. the case of the eclipsing binary Cepheid CEP0227 in the Large Magellanic Cloud
• The Eclipsing Binary Cepheid OGLE-LMC-CEP-0227 in the Large Magellanic Cloud: pulsation modelling of light and radial velocity curves
• A Classical Cepheid in a LMC eclipsing binary: evidence of shortcomings in current stellar evolutionary models?
• The Araucaria Project: High-precision Cepheid astrophysics from the analysis of variables in double-lined eclipsing binaries
• Stellar convective penetration: parameterized theory and dynamical simulations
• A geometrical 1% distance to the short-period binary Cepheid V1334 Cygni
• The Araucaria Project: The First-Overtone Classical Cepheid in the Eclipsing System OGLE-LMC-CEP-2532
• The VMC survey -- XLIV: Mapping metallicity trends in the Large Magellanic Cloud using near-infrared passbands
• Classical Cepheids Require Enhanced Mass Loss
• The Araucaria Project. Accurate determination of the dynamical mass of the classical Cepheid in the eclipsing system OGLE-LMC-CEP-1812
• The Araucaria Project: A study of the classical Cepheid in the eclipsing binary system OGLE LMC562.05.9009 in the Large Magellanic Cloud
• Core Overshoot: An Improved Treatment and Constraints from Seismic Data
• Investigating the Consistency of Stellar Evolution Models with Globular Cluster Observations via the Red Giant Branch Bump
• The Araucaria Project. OGLE-LMC-CEP-1718: An exotic eclipsing binary system composed of two classical overtone Cepheids in a 413-day orbit
• On a new parameter to estimate the helium content in old stellar systems
• Stellar evolution models with overshooting based on 3-equation non-local theories, II. Main-sequence models of A- and B-type stars
• The strange evolution of the Large Magellanic Cloud Cepheid OGLE-LMC-CEP1812
• Stellar evolution models with overshooting based on 3-equation non-local theories I. Physical basis and the computation of the dissipation rate
• Stellar age determination in the Mass-Luminosity Plane
• Testing a non-local 1-equation turbulent convection model: A solar model

Cited by in corpus (5)

• Toward a Comprehensive Grid of Cepheid Models with MESA. III. Evolutionary and Pulsation Relations for Models with Core and Envelope Overshooting
• The light curve model fitting of LMC Cepheids: MESA-RSP versus Stellingwerf's code predictions
• Empirical instability strip for classical Cepheids II. The Small Magellanic Cloud galaxy
• Toward a Comprehensive Grid of Cepheid Models with MESA. IV. Modest Effects of Rotation on Blue Loops
• Testing the 3-equation Kuhfuss Convection Model using the Sun