A test of time-dependent theories of stellar convection

Abstract

Context: In Cepheids close to the red edge of the classical instability strip, a coupling occurs between the acoustic oscillations and the convective motions close to the surface.The best topical models that account for this coupling rely on 1-D time-dependent convection (TDC) formulations. However, their intrinsic weakness comes from the large number of unconstrained free parameters entering in the description of turbulent convection. Aims: We compare two widely used TDC models with the first two-dimensional nonlinear direct numerical simulations (DNS) of the convection-pulsation coupling in which the acoustic oscillations are self-sustained by the kappa-mechanism. Methods: The free parameters appearing in the Stellingwerf and Kuhfuss TDC recipes are constrained using a chi2-test with the time-dependent convective flux that evolves in nonlinear simulations of highly-compressible convection with kappa-mechanism. Results: This work emphasises some inherent limits of TDC models, that is, the temporal variability and non-universality of their free parameters. More importantly, within these limits, Stellingwerf's formalism is found to give better spatial and temporal agreements with the nonlinear simulation than Kuhfuss's one. It may therefore be preferred in 1-D TDC hydrocodes or stellar evolution codes.

7 pages, 5 figures, 2 tables, accepted for publication in A&A

References in corpus (5)

• Spectrum and amplitudes of internal gravity waves excited by penetrative convection in solar-type stars
• Non-linear modelling of beat Cepheids: Resonant and non-resonant models
• DNS of the kappa-mechanism. I. Radial modes in the purely radiative case
• Direct numerical simulations of the kappa-mechanism II. The nonlinear saturation and Hertzsprung's progression
• Convective quenching of stellar pulsations

Cited by in corpus (5)

• Episodic mass ejections from common-envelope objects
• Pulsations of red supergiant pair-instability supernova progenitors leading to extreme mass loss
• Multidimensional realistic modelling of Cepheid-like variables. I: Extensions of the ANTARES code
• Convection, granulation and period jitter in classical Cepheids
• Multidimensional realistic modelling of Cepheid-like variables-II: Analysis of a Cepheid model