A nonlinear convective model for radial stellar pulsations

Feuchtinger, M. U.

doi:10.1051/aas:1999462

Cited by 32 publications

(23 citation statements)

References 17 publications

(21 reference statements)

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“…Yecko et al 1998 and references therein). Despite the lack of a robust theory, it has now become clear that convective energy transport is essential to describe the observed properties of pulsating stars such as light curves or Fourier coefficients (Yecko et al 1998;Feuchtinger 1999;Feuchtinger et al 2000).…”

Section: Uncertainties On Distance Determinationmentioning

confidence: 99%

Period -magnitude relationships inBVIJHK-bands for fundamental mode and first overtone Cepheids

Baraffe

Alibert

2001

A&A

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Abstract. We present theoretical period -magnitude relationships for Cepheids in different filters for fundamental and first overtone pulsators, completing the work by Alibert et al. (1999). The results are provided for different metallicities characteristic of the Magellanic Clouds and the Milky Way. In contrast to the fundamental mode, we find a small metallicity effect on the period -luminosity relationship for the first overtone, due to the sensitivity of the period ratio P1/P0 with metallicity. Comparison is made with observations from OGLE and EROS in the Small and Large Magellanic Clouds. We emphasize the constraint on theoretical predictions provided by the combination of both fundamental and first overtone observed sequences. We obtain excellent agreement between models and data in a log P -WI (Wesenheit index) diagram for a distance modulus for the LMC µ0 = 18.60 -18.70. We analyse the uncertainties of the fundamental period -magnitude relationships and the consequences on distance determination. We show that an arbitrary shift of the instability strip by 350 K in T eff yields up to 0.45 mag effect on MV at a given period, whereas the effect is less than 0.1 mag in the K-band. Using recent near-IR observations in the Large Magellanic Cloud and our P -MK relationship, we derive a distance modulus for the LMC in agreement with the value based on WI data.

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Section: Uncertainties On Distance Determinationmentioning

confidence: 99%

Period -magnitude relationships inBVIJHK-bands for fundamental mode and first overtone Cepheids

Baraffe

Alibert

2001

A&A

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“…This formalism for the viscosity in the radial direction closely resembles -except of course for the shear part -the customary 1D viscosity description given, e.g., by Dorfi (1998) or Feuchtinger (1999a. In the horizontal direction, discretization yields a viscous force…”

Section: Artificial Viscositymentioning

confidence: 70%

A two-column formalism for time-dependent modelling of stellar convection

Stökl¹

2008

A&A

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Context. In spite of all the advances in multi-dimensional hydrodynamics, investigations of stellar evolution and stellar pulsations still depend on one-dimensional computations. This paper devises an alternative to the mixing-length theory or turbulence models usually adopted in modelling convective transport in such studies. Aims. The present work attempts to develop a time-dependent description of convection, which reflects the essential physics of convection and that is only moderately dependent on numerical parameters and far less time consuming than existing multi-dimensional hydrodynamics computations. Methods. Assuming that the most extensive convective patterns generate the majority of convective transport, the convective velocity field is described using two parallel, radial columns to represent up-and downstream flows. Horizontal exchange, in the form of fluid flow and radiation, over their connecting interface couples the two columns and allows a simple circulating motion. The main parameters of this convective description have straightforward geometrical meanings, namely the diameter of the columns (corresponding to the size of the convective cells) and the ratio of the cross-section between up-and downdrafts. For this geometrical setup, the time-dependent solution of the equations of radiation hydrodynamics is computed from an implicit scheme that has the advantage of being unaffected by the Courant-Friedrichs-Lewy time-step limit. This implementation is part of the TAPIR-Code (short for The adaptive, implicit RHD-Code). Results. To demonstrate the approach, results for convection zones in Cepheids are presented. The convective energy transport and convective velocities agree with expectations for Cepheids and the scheme reproduces both the kinetic energy flux and convective overshoot. A study of the parameter influence shows that the type of solution derived for these stars is in fact fairly robust with respect to the constitutive numerical parameters.

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“…The inclusion of the convective stellar mantle in the model requires the use of either a three-dimensional approach (such as presented by Freytag & Höfner 2008) or a description for turbulent energy (see e.g. Kuhfuß 1986;Gehmeyr & Winkler 1992;Canuto & Dubovikov 1998;Wuchterl & Feuchtinger 1998;Feuchtinger 1999), which implies a number of additional free parameters. It should, however, be possible to set many of these new parameters to default values.…”

Section: Modeling Mass-loss Formation Near the Tip Of The Agbmentioning

confidence: 99%

Measuring Mass-Loss Evolution at the Tip of the Asymptotic Giant Branch

Sandín

Roth

Schönberner

2010

Publ. – Astron. Soc. Aust

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Abstract:In the final stages of stellar evolution low-to intermediate-mass stars lose their envelope in increasingly massive stellar winds. Such winds affect the interstellar medium and the galactic chemical evolution as well as the circumstellar envelope where planetary nebulae form subsequently. Characteristics of this mass loss depend on both stellar properties and properties of gas and dust in the wind formation region. In this paper we present an approach towards studies of mass loss using both observations and models, focussing on the stage where the stellar envelope is nearly empty of mass. In a recent study we measure the mass-loss evolution, and other properties, of four planetary nebulae in the Galactic disk. Specifically we use the method of integral field spectroscopy on faint halos, which are found outside the much brighter central parts of a planetary nebula. We begin with a brief comparison between our and other observational methods to determine mass-loss rates in order to illustrate how they differ and complement each other. An advantage of our method is that it measures the gas component directly requiring no assumptions of properties of dust in the wind. Thereafter we present our observational approach in more detail in terms of its validity and its assumptions. In the second part of this paper we discuss capabilities and assumptions of current models of stellar winds. We propose and discuss improvements to such models that will allow meaningful comparisons with our observations. Currently the physically most complete models include too little mass in the model domain to permit a formation of winds with as high mass-loss rates as our observations show.

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A nonlinear convective model for radial stellar pulsations

Cited by 32 publications

References 17 publications

Period -magnitude relationships inBVIJHK-bands for fundamental mode and first overtone Cepheids

Period -magnitude relationships inBVIJHK-bands for fundamental mode and first overtone Cepheids

A two-column formalism for time-dependent modelling of stellar convection

Measuring Mass-Loss Evolution at the Tip of the Asymptotic Giant Branch

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