scholarly journals Hydrostatic equilibrium and stellar structure inf(R)gravity

2011 ◽  
Vol 83 (6) ◽  
Author(s):  
S. Capozziello ◽  
M. De Laurentis ◽  
S. D. Odintsov ◽  
A. Stabile
Keyword(s):  
Hydrostatic Equilibrium ◽  
Stellar Structure

scholarly journals A Model for Adiabatic Mass-loss

2008 ◽  
Vol 4 (S252) ◽  
pp. 419-420
Author(s):  
Hongwei. Ge ◽  
R. F. Webbink ◽  
Z. Han
Keyword(s):  
Heat Flow ◽  
Mass Loss ◽  
Hydrostatic Equilibrium ◽  
Stellar Structure ◽  
Close Binary ◽  
Common Envelope ◽  
Compute Model ◽  
Binary Evolution ◽  
Structure Code

AbstractWe describe our work on the development and application of a stellar structure code to compute model sequences representing donor stars in interacting binaries subject to rapid (adiabatic) mass-loss. The donor star is assumed to remain in hydrostatic equilibrium, but no heat flow is allowed. These sequences can be used to define bifurcation sequences in close binary evolution, and to circumscribe possible survivors of common envelope evolution.

EQUATION OF STELLAR STRUCTURE IN HAYASHI’S NEW GENERAL RELATIVITY

1995 ◽  
Vol 10 (15) ◽  
pp. 2225-2230 ◽  
Author(s):  
C.M. ZHANG ◽  
P.D. ZHAO
Keyword(s):  
General Relativity ◽  
Coordinate System ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Hydrostatic Equilibrium ◽  
Stellar Structure ◽  
Gravitation Theory ◽  
Tetrad Field

The general form of the parallelism tetrad field in the Schwarzschild coordinate system is presented in the framework of Hayashi’s gravitation theory with torsion. In the case of the symmetric energy-momentum tensor, we obtain the approximated equation of stellar structure, which, as a limit, is the Oppenheimer-Volkoff equation for hydrostatic equilibrium in general relativity.

scholarly journals Invariant quantities of scalar–tensor theories for stellar structure

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Aleksander Kozak ◽  
Aneta Wojnar
Keyword(s):  
Wide Class ◽  
Hydrostatic Equilibrium ◽  
Stellar Structure ◽  
Tensor Representation ◽  
Equilibrium Equations ◽  
Tensor Invariants ◽  
Physical Role ◽  
Gravitational Theories ◽  
Structure Equations

AbstractWe present the relativistic hydrostatic equilibrium equations for a wide class of gravitational theories possessing a scalar–tensor representation. It turns out that the stellar structure equations can be written with respect to the scalar–tensor invariants, allowing to interpret their physical role.

scholarly journals A Dialogue on Dynamical Pre-Main Sequence Tracks

2001 ◽  
Vol 200 ◽  
pp. 492-495 ◽  
Author(s):  
Günther Wuchterl
Keyword(s):  
Main Sequence ◽  
Thermal Structure ◽  
Brown Dwarfs ◽  
Young Star ◽  
Hydrostatic Equilibrium ◽  
Young Stars ◽  
Stellar Atmospheres ◽  
Stellar Structure ◽  
Sequence Evolution ◽  
Stellar Matter

Based on the theory of stellar structure and evolution combined with the theory of stellar atmospheres theoretical properties of young stars can be calculated. These calculations of pre-main sequence evolution have been refined over the last decades and do now provide theoretical spectra and colours even for very cool objects like young stars brown dwarfs and planets. Two of their key assumptions must become invalid towards the formation phases: (1) the hydrostatic equilibrium of pressure forces and gravity that assumes stellar matter to be at rest and (2) the non-dependence on the initial thermal structure. The former (1) is violated by accretion- and collapse flows, the latter (2) because a new born young star is observed with the specific thermal structure produced by the cloud collapse. I discuss changes in the theoretical properties of young stars that follow from calculating the pre-main sequence evolution as the consequence of the collapse of Bonnor-Ebert spheres.

scholarly journals Stellar Structure in a Newtonian Theory with Variable G

Physics ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 1123-1132
Author(s):  
Júlio C. Fabris ◽  
Túlio Ottoni ◽  
Júnior D. Toniato ◽  
Hermano Velten
Keyword(s):  
Spatial Dependence ◽  
Equilibrium Structure ◽  
Hydrostatic Equilibrium ◽  
Stellar Structure ◽  
Polytropic Index ◽  
Gravitational Coupling ◽  
Matter Distribution ◽  
Newtonian Theory ◽  
Emden Equation ◽  
Variable G

A Newtonian-like theory inspired by the Brans–Dicke gravitational Lagrangian has been recently proposed by us. For static configurations, the gravitational coupling acquires an intrinsic spatial dependence within the matter distribution. Therefore, the interior of astrophysical configurations may provide a testable environment for this approach as long as no screening mechanism is evoked. In this work, we focus on the stellar hydrostatic equilibrium structure in such a varying Newtonian gravitational coupling G scenario. A modified Lane–Emden equation is presented and its solutions for various values of the polytropic index are discussed. The role played by the theory parameter ω, the analogue of the Brans–Dicke parameter, in the physical properties of stars is discussed.

scholarly journals An extensive photometric study of the Blazhko RR Lyrae star RZ Lyr*

2012 ◽  
Vol 423 (2) ◽  
pp. 993-1005 ◽  
Author(s):  
J. Jurcsik ◽  
Á. Sódor ◽  
G. Hajdu ◽  
B. Szeidl ◽  
Á. Dózsa ◽  
...  
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Stellar Structure ◽  
Time Base ◽  
Photometric Method ◽  
Physical Parameters ◽  
Component Solution ◽  
Rr Lyrae ◽  
Curve Variation ◽  
Type Variable

Abstract The analysis of recent, extended multicolour CCD and archive photoelectric, photographic and visual observations has revealed several important properties of RZ Lyr, an RRab-type variable exhibiting large-amplitude Blazhko modulation. On the time base of ∼110 yr, a strict anticorrelation between the pulsation- and modulation-period changes is established. The light curve of RZ Lyr shows a remarkable bump on the descending branch in the small-amplitude phase of the modulation, similarly to the light curves of bump Cepheids. We speculate that the stellar structure temporally suits a 4:1 resonance between the periods of the fundamental and one of the higher order radial modes in this modulation phase. The light-curve variation of RZ Lyr can be correctly fitted with a two-modulation-component solution; the 121-d period of the main modulation is nearly but not exactly four times longer than the period of the secondary modulation component. Using the inverse photometric method, the variations in the pulsation-averaged values of the physical parameters in different phases of both modulation components are determined.

scholarly journals Solar structure and evolution

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Jørgen Christensen-Dalsgaard
Keyword(s):  
Solar Surface ◽  
Solar Neutrinos ◽  
Solar Interior ◽  
Stellar Structure ◽  
The Sun ◽  
Physical Processes ◽  
Solar Evolution ◽  
Internal Properties ◽  
Atmospheric Phenomena

AbstractThe Sun provides a critical benchmark for the general study of stellar structure and evolution. Also, knowledge about the internal properties of the Sun is important for the understanding of solar atmospheric phenomena, including the solar magnetic cycle. Here I provide a brief overview of the theory of stellar structure and evolution, including the physical processes and parameters that are involved. This is followed by a discussion of solar evolution, extending from the birth to the latest stages. As a background for the interpretation of observations related to the solar interior I provide a rather extensive analysis of the sensitivity of solar models to the assumptions underlying their calculation. I then discuss the detailed information about the solar interior that has become available through helioseismic investigations and the detection of solar neutrinos, with further constraints provided by the observed abundances of the lightest elements. Revisions in the determination of the solar surface abundances have led to increased discrepancies, discussed in some detail, between the observational inferences and solar models. I finally briefly address the relation of the Sun to other similar stars and the prospects for asteroseismic investigations of stellar structure and evolution.

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