scholarly journals Constraints on stellar evolution theory from precise eclipsing binary data

1984 ◽  
Vol 105 ◽  
pp. 391-394
Author(s):  
J. Andersen ◽  
J.V. Clausen ◽  
H.E. J⊘rgensen ◽  
B. Nordström
Keyword(s):  
Stellar Evolution ◽  
Binary Data ◽  
Main Sequence ◽  
Theoretical Models ◽  
Stellar Structure ◽  
Sequence Evolution ◽  
Evolution Theory ◽  
Eclipsing Binary ◽  
Standard Models ◽  
Structure Calculations

Previous attempts at a detailed confrontation of eclipsing binary data with theoretical models of main-sequence evolution were faced with the choice between data of inhomogeneous (mostly low) quality for many systems (Kriz, 1969; Lacy, 1979) or accurate values of mass, radius, and temperature (or luminosity) for very few systems only (Popper et al., 1970). In addition, more detailed and homogeneous stellar structure calculations for several compositions were needed. Since 1972, a coordinated photometric and spectroscopic programme at our institute contributes to building a sufficient observational basis for such a test. Among published standard models for the range 1–10 M⊙, Hejlesen's (1980) are the most extensive, agree well with other standard models, and are presented in a format suitable for comparison with binary data. Here we can only outline a few salient new results from this study.

scholarly journals Constraints on pre-main-sequence evolution from stellar pulsations

2013 ◽  
Vol 9 (S301) ◽  
pp. 137-144
Author(s):  
M. P. Casey ◽  
K. Zwintz ◽  
D. B. Guenther
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Sequence Evolution ◽  
B Stars ◽  
Stellar Pulsations ◽  
Pms Stars

AbstractPulsating pre-main-sequence (PMS) stars afford the earliest opportunity in the lifetime of a star to which the concepts of asteroseismology can be applied. PMS stars should be structurally simpler than their evolved counterparts, thus (hopefully!) making any asteroseismic analysis relatively easier. Unfortunately, this isn't necessarily the case. The majority of these stars (around 80) are δ Scuti pulsators, with a couple of γ Doradus, γ Doradus – δ Scuti hybrids, and slowly pulsating B stars thrown into the mix. The majority of these stars have only been discovered within the last ten years, with the community still uncovering the richness of phenomena associated with these stars, many of which defy traditional asteroseismic analysis.A systematic asteroseismic analysis of all of the δ Scuti PMS stars was performed in order to get a better handle on the properties of these stars as a group. Some strange results have been found, including one star pulsating up to the theoretical acoustic cut-off frequency of the star, and a number of stars in which the most basic asteroseismic analysis suggests problems with the stars' positions in the Hertzsprung-Russell diagram. From this we get an idea of the\break constraints — or lack thereof — that these results can put on PMS stellar evolution.

scholarly journals Small and Intermediate Mass Stellar Evolution - Main Sequence and Close to It

1993 ◽  
Vol 137 ◽  
pp. 410-425 ◽  
Author(s):  
A. Noels ◽  
N. Grevesse
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Turbulent Diffusion ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
Physical Mechanisms ◽  
Standard Models

AbstractWe present the standard models for small and intermediate main sequence stars and we discuss some of the problems arising with semiconvection and overshooting. The surface abundance of Li serves as a test for other physical mechanisms, including microscopic and turbulent diffusion, rotation and mass loss.

scholarly journals Modelling of an Eclipsing RS CVn Binary: V405 And

2011 ◽  
Vol 7 (S282) ◽  
pp. 199-200
Author(s):  
Krisztián Vida ◽  
Katalin Oláh ◽  
Zsolt Kővári
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Magnetic Activity ◽  
Light Curves ◽  
Stellar Structure ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Primary Star ◽  
Convective Envelope ◽  
Eclipsing Binary

AbstractV405 And is an ultrafast-rotating (Prot ≈ 0.46 days) eclipsing binary. The system consists of a primary star with radiative core and convective envelope, and a fully convective secondary. Theories have shown that stellar structure can depend on magnetic activity, i.e., magnetically active M-dwarfs should have larger radii. Earlier light curve modelling of V405 And indeed showed this behaviour: we found that the radius of the primary is significantly larger than the theoretically predicted value for inactive main sequence stars (the discrepancy is the largest of all known objects), while the secondary fits well to the mass-radius relation. By modelling our recently obtained light curves, which show significant changes of the spotted surface of the primary, we can find further proof for this phenomenon.

scholarly journals Angular Momentum Loss in Post-Main Sequence Stellar Evolution Through the PN Stage

1993 ◽  
Vol 155 ◽  
pp. 368-368
Author(s):  
M. Villata
Keyword(s):  
Angular Momentum ◽  
Stellar Evolution ◽  
White Dwarf ◽  
Main Sequence ◽  
Sequence Evolution ◽  
Simple Analytical Model ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Pn Stage ◽  
Large Angular Momentum

A simple analytical model can explain the large angular momentum loss which a star suffers in its post-main-sequence evolution up to the white dwarf stage.

scholarly journals Massive star evolution revealed in the Mass-Luminosity plane

2018 ◽  
Vol 14 (S346) ◽  
pp. 480-485
Author(s):  
Erin R. Higgins ◽  
Jorick S. Vink
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Star ◽  
Main Sequence ◽  
Theoretical Models ◽  
Physical Processes ◽  
Single Star ◽  
Star Evolution ◽  
Novel Method ◽  
Massive Star Evolution

AbstractMassive star evolution is dominated by key physical processes such as mass loss, convection and rotation, yet these effects are poorly constrained, even on the main sequence. We utilise a detached, eclipsing binary HD166734 as a testbed for single star evolution to calibrate new MESA stellar evolution grids. We introduce a novel method of comparing theoretical models with observations in the ‘Mass-Luminosity Plane’, as an equivalent to the HRD (see Higgins & Vink 2018). We reproduce stellar parameters and abundances of HD166734 with enhanced overshooting (αov=0.5), mass loss and rotational mixing. When comparing the constraints of our testbed to the systematic grid of models we find that a higher value of αov=0.5 (rather than αov=0.1) results in a solution which is more likely to evolve to a neutron star than a black hole, due to a lower value of the compactness parameter.

scholarly journals Stellar models of rotating, pre-main sequence low-mass stars with magnetic fields

2013 ◽  
Vol 9 (S302) ◽  
pp. 112-113 ◽  
Author(s):  
Luiz T. S. Mendes ◽  
Natália R. Landin ◽  
Luiz P. R. Vaz
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Large Scale ◽  
Main Sequence ◽  
Stellar Structure ◽  
Low Mass Stars ◽  
Large Scale Magnetic Field ◽  
Low Mass ◽  
Structure Equations ◽  
Stellar Models

AbstractWe report our present efforts for introducing magnetic fields in the ATON stellar evolution code code, which now evolved to truly modifying the stellar structure equations so that they can incorporate the effects of an imposed, large-scale magnetic field. Preliminary results of such an approach, as applied to low-mass stellar models, are presented and discussed.

scholarly journals Globular cluster ages from main sequence fitting and detached, eclipsing binaries: The case of 47 Tuc

2008 ◽  
Vol 4 (S258) ◽  
pp. 171-176 ◽  
Author(s):  
Aaron Dotter ◽  
Janusz Kaluzny ◽  
Ian B. Thompson
Keyword(s):  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Eclipsing Binary ◽  
Age Constraints

AbstractAge constraints are most often placed on globular clusters by comparing their CMDs with theoretical isochrones. The recent discoveries of detached, eclipsing binaries in such systems by the Cluster AgeS Experiment (CASE) provide new insights into their ages and, at the same time, provide much-needed tests of stellar evolution models. We describe efforts to model the properties of the detached, eclipsing binary V69 in 47 Tuc and compare age constraints derived from stellar evolution models of V69A and B with ages obtained from fitting isochrones to the cluster CMD. We determine whether or not, under reasonable assumptions of distance, reddening, and metallicity, it is possible to simultaneously constrain the age and He content of 47 Tuc.

scholarly journals Comparisons between observational color-magnitude diagrams and synthetic cluster diagrams for young star clusters in the Magellanic Clouds

1984 ◽  
Vol 105 ◽  
pp. 83-87
Author(s):  
Stephen A. Becker ◽  
Grant J. Mathews ◽  
Wendee M. Brunish
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Star Clusters ◽  
Theoretical Models ◽  
Young Star ◽  
Asymptotic Giant Branch ◽  
Current Status ◽  
Large Numbers ◽  
Young Star Clusters ◽  
Convective Overshoot

Young star clusters (<3 × 108 yr) in the Maqellanic Clouds (MC) can be used to test the current status of the theory of stellar evolution as applied to intermediate and massive stars. The color-magnitude diagram of many young clusters in the MC shows, unlike the case of clusters in our Galaxy, large numbers of stars in both the main sequence and post main sequence evolutionary phases. Usina a arid of stellar evolution models, synthetic cluster H-R diagrams are constructed and compared to observed color-magnitude diagrams to determine the age, age spread, and composition for any given cluster. In addition, for those cases where the data is of high quality, detailed comparisons between theory and observation can provide a diagnostic of the accuracy of the stellar evolution models. Initial indications of these comparisons suggest that the theoretical models should be altered to include: a larger value for the mixing length parameter (α), a larger rate of mass loss during the asymptotic giant branch (AGB) phase, and possibly convective overshoot during the core burning phases.

scholarly journals A Stringent Test of Magnetic Models of Stellar Evolution

Galaxies ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 3
Author(s):  
Guillermo Torres ◽  
Gregory A. Feiden ◽  
Andrew Vanderburg ◽  
Jason L. Curtis
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Open Cluster ◽  
Main Sequence Stars ◽  
Robust Estimates ◽  
Empirical Estimates ◽  
Nonstandard Models ◽  
Stringent Test ◽  
Standard Models ◽  
The Magnetic Field

Main-sequence stars with convective envelopes often appear larger and cooler than predicted by standard models of stellar evolution for their measured masses. This is believed to be caused by stellar activity. In a recent study, accurate measurements were published for the K-type components of the 1.62-day detached eclipsing binary EPIC 219511354, showing the radii and temperatures for both stars to be affected by these discrepancies. This is a rare example of a system in which the age and chemical composition are known, by virtue of being a member of the well-studied open cluster Ruprecht 147 (age~3 Gyr, [Fe/H] = +0.10). Here, we report a detailed study of this system with nonstandard models incorporating magnetic inhibition of convection. We show that these calculations are able to reproduce the observations largely within their uncertainties, providing robust estimates of the strength of the magnetic fields on both stars: 1600 ± 130 G and 1830 ± 150 G for the primary and secondary, respectively. Empirical estimates of the magnetic field strengths based on the measured X-ray luminosity of the system are roughly consistent with these predictions, supporting this mechanism as a possible explanation for the radius and temperature discrepancies.

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