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2 edition of Pulsatations of stellar envelopes with convection zones found in the catalog.

Pulsatations of stellar envelopes with convection zones

Bruce Clayton Cogan

Pulsatations of stellar envelopes with convection zones

by Bruce Clayton Cogan

  • 44 Want to read
  • 40 Currently reading

Published by University of Michigan in [East Lansing .
Written in English

    Subjects:
  • Pulsating stars,
  • Cepheids

  • Classifications
    LC ClassificationsQB838 C6 1967a
    The Physical Object
    Paginationv, 70 leaves :
    Number of Pages70
    ID Numbers
    Open LibraryOL18725201M

    The seismic study of the transition in the Sun, located at the base of the convection zone, has been successful in determining the characteristics of this layer in the Sun. In this work we consider the extension of the analysis to other solar-type stars (of mass between and M ⊙) in order to establish a method for determining the.   This book brings together for the first time recent results in solar studies and stellar studies. The result is an illuminating new view of stellar magnetic activity. Key topics include radiative transfer, convective simulations, dynamo theory, outer-atmospheric heating, stellar winds and 5/5(1).

    The asymptotic giant branch is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars late in their lives. Observationally, an asymptotic-giant-branch star will appear as a bright red giant with a luminosity ranging up to thousands of times greater than the Sun. Its interior structure is characterized . Modelling of pulsations of giant stars erties of these stars. As is well-known, a red giant star has an extended convective envelope (more than 90 percents of stellar radius), making the treatment of convection to be very important for namical modelling of the surface and the outer part of the convection zones of the giant stars. A.

    stellar masses and densities. Pulsations can be regular, irregular, interacting, or stochastic in nature and generally stem from an interplay between thermodynamics and gravitational forces. The two main types of pulsations are termed p-mode (pressure restoring forces) and g-mode (gravity/buoyancy restoring forces). Both the envelopes. In this review I present an overview of our current understanding of the physical mechanisms that are responsible for the excitation of pulsations in stars.


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Pulsatations of stellar envelopes with convection zones by Bruce Clayton Cogan Download PDF EPUB FB2

The pulsation is in fact a standing pressure wave, driven in the ionization zone in the envelope and traveling between the Pulsatations of stellar envelopes with convection zones book center and the surface of the star.

Because the temperature structure in the different types of stars is not the same, the sound speed crossing time depends on the evolutionary phase, so the constants C and Q are. One zone modeling of the irregular variability of red super-giants is intended with regard to the nonlinear coupling of finite amplitude pulsation with convection.

The nonlocal mixing length is One Zone Modeling of Irregular Variability of Stellar Convective Envelope | SpringerLinkCited by: 2. One zone modeling of the irregular variability of red super-giants is intended with regard to the nonlinear coupling of finite amplitude pulsation with convection.

The nonlocal mixing length is employed for the evaluation of the convective flux, the turbulent pressure and the turbulent power of temperature by: 2. A version of the one-zone model, the weakly coupled monomode model, is derived, showing that the small parameter in stellar pulsation is the coupling term in the momentum equation.

A crude model of similar derivation is found that describes a portion of the convection-pulsation interaction. pulsation timescale (∼ s), it is possible to use the pulsations themselves to sample and constrain the convection zones of these stars (Ising & KoesterMontgomery, in preparation).

Con-sequently, other than the well-studied convection zone of the Sun, white dwarfs may offer the best chance for testing theories of stellar convection.

M.U. Feuchtinger: A nonlinear convective model for radial stellar pulsations. Physical description In order to describe the nonlinear behavior of pulsating stars we assume the stellar plasma to consist of three com-ponents, namely gas, radiation and turbulent convection.

The evolution of each component is governed by respec. The envelopes of smaller, cooler, main-sequence stars are also dominated by convection. The extent of these outer convection zones may have an e ect on the surface abundances of di erent chemical species.

In general, the depth of the convective envelope in stars cooler. Our goals are to examine the interaction of stellar pulsations with turbulent convection in the envelope, excitation of acoustic modes, and the role of convective overshooting; 2) Applying the spherical 3-D MHD ASH (Anelastic Spherical Harmonics) code to simulate the core convection and radiative zone.

Detection of The Lower Boundary of Stellar Convective Envelopes from Seismic Data Article (PDF Available) in Astrophysics and Space Science () January with 13 Reads. stellar envelopes. Multidimensional simulations of sub-surface convection zones and a larger number of high-quality observations are necessary to test this idea more rigorously.

Key words. star: massive mass - convection zone - turbulence - pulsations - Magellanic Clouds 1. Introduction The Large and Small Magellanic Clouds (LMC and SMC) are.

PDF | On Jan 1,MJPFG Monteiro and others published On the seismic signature of the HeII ionization zone in stellar envelopes | Find, read and cite all the research you need on ResearchGate. The helium abundance in stellar convective envelope has almost no essential influence on the red (low-temperature) boundary of the δ Scuti variable pulsation-instability region; but as the helium abundance decreases, the blue (high-temperature) boundary of the pulsation-instability region moves toward the direction of low temperatures, and the δ Scuti pulsation-instability region becomes by: 1.

The pulsations are driven by the modulation of radiative flux by convection at the base of a deep envelope convection zone. Pulsation instability is predicted only for models with temperatures at the convection zone base between {approximately}, and {approximately}, K.

and million K, in addition to the Z-bump region aroundK. We use different stellar evolution and pulsation codes than those used in previous studies. We show the effects of opacity enhancements on inducing and widening convection zones and increasing convective velocities, in the context of the mixing-length theory of convection [18].

Abstract Homogeneous models of luminous hydrogen-and-helium burning stars were constructed on the basis of Carson's new radiative opacities. These opacities exhibit a large 'bump' at moderate temperatures and low densities as a result of the ultimate ionization of the CNO group of elements and they induce in the envelopes of the more massive stars a strong local convection zone, a high.

Delta Scuti (δ Sct)1 stars are opacity-driven pulsators with masses of –M⊙, their pulsations resulting from the varying ionization of helium. In less massive stars2 such as the Sun. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): Abstract.

The influence of extended convective mixing (overshoot) on asymptotic giant branch stellar evolution is investigated in detail. The extended mixing is treated timedependently, and the efficiency declines exponentially with the geometric distance from the convective boundary.

CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): ABSTRACT. Observations of heavy elements in Red Giant stars clearly show that low-mass AGB stars can provide a nucleosynthesis site of the s-process.

Stellar evolution models produced over the last years indicate that radiative burning of 13 C between succeeding thermal pulses in low-mass AGB star models may.

the sluggish convection rapidly enough to prevent an outward accelera- tion of much of the envelope. As the helium abundance in the envelope stellar material increases by ordinary wind mass loss and the luminous blue variable outbursts, the opacity in the deep pulsation driving layers decreases.

The pulsation theory of red giant stars is still very inexact compared to similar theories for warmer variables such as Cepheids and RR Lyraes.

The main reason for our poor understanding of variable red giants is that convection dominates energy transport in the envelope, the part of the star to which the pulsation is confined.

Modeling stellar pulsations (mostly correctly) László Molnár Konkoly Observatory, MTA CSFK, Budapest. Motivations Envelope divided into movable zones (one or more) Convection is important for the pulsation!Pulsations give us a differential view of a star: • not limited to global quantities such as Te and logg • get a dynamic versus a static picture • can ‘see inside’ the stars, study stellar interiors (‘helio- and asteroseismology’) • potential to measure rotation (solid body and differential) • find thickness of convection zones.The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous is a period of stellar evolution undertaken by all low- to intermediate-mass stars (–10 solar masses) late in their lives.

Observationally, an asymptotic-giant-branch star will appear as a bright red giant with a luminosity ranging up to thousands of times.