scholarly journals Tests of Evolution Models Using Eclipsing Binaries

1995 ◽  
Vol 10 ◽  
pp. 419-422
Author(s):  
J. Andersen
Keyword(s):  
Chemical Composition ◽  
Star Clusters ◽  
Stellar Model ◽  
Eclipsing Binaries ◽  
Fundamental Parameter ◽  
Fundamental Parameters ◽  
Stellar Models ◽  
Absolute Age ◽  
Cluster Sequence ◽  
Hr Diagram

Stellar models are the means by which we describe and understand the distribution of stars in the HR diagram. A stellar model is, in principle, completely specified by the three fundamental parameters mass, chemical composition, and age. Comparing the properties of models and real stars with the same parameters will tell us if our recipe for constructing stellar models is realistic. Unfortunately, the only star for which all three are known independently of stellar models is the Sun. For stars of other masses and ages we must devise observational tests in which at least one fundamental parameter is unknown. Two such popular test objects are double-lined eclipsing binaries and star clusters.In suitable eclipsing binaries we can determine both masses and chemical composition; the absolute age is unknown, but the same for both stars. Since evolution depends most sensitively on the mass, eclipsing binaries provide a very direct test of the models, but only for two points on a single isochrone. In star clusters, neither ages nor individual masses are known, but the detailed shape and population of a well-observed cluster sequence in the HR diagram provide a number of additional probes into the models.

scholarly journals Eclipsing Binaries in Open Clusters

2006 ◽  
Vol 2 (S240) ◽  
pp. 619-621
Author(s):  
John Southworth
Keyword(s):  
Chemical Composition ◽  
Observational Data ◽  
Open Cluster ◽  
Type Systems ◽  
Open Clusters ◽  
Eclipsing Binaries ◽  
Young Open Cluster ◽  
Stellar Models ◽  
Additional Constraints ◽  
Absolute Parameters

AbstractDetached eclipsing binaries are very useful objects for calibrating theoretical stellar models and checking their predictions. Detached eclipsing binaries in open clusters are particularly important because of the additional constraints on their age and chemical composition from their membership of the cluster. I compile a list containing absolute parameters of well-studied eclipsing binaries in open clusters, and present new observational data on the B-type systems V1481 Cyg and V2263 Cyg which are members of the young open cluster NGC 7128.

scholarly journals Effective temperatures of red giants in the APOKASC catalogue and the mixing length calibration in stellar models

2018 ◽  
Vol 612 ◽  
pp. A68 ◽  
Author(s):  
M. Salaris ◽  
S. Cassisi ◽  
R. P. Schiavon ◽  
A. Pietrinferni
Keyword(s):  
Chemical Composition ◽  
Boundary Conditions ◽  
Effective Temperature ◽  
Outer Boundary ◽  
Stellar Model ◽  
Red Giants ◽  
Mixing Length ◽  
Important Conclusion ◽  
Model Calculations ◽  
Stellar Models

Red giants in the updated APOGEE-Kepler catalogue, with estimates of mass, chemical composition, surface gravity and effective temperature, have recently challenged stellar models computed under the standard assumption of solar calibrated mixing length. In this work, we critically reanalyse this sample of red giants, adopting our own stellar model calculations. Contrary to previous results, we find that the disagreement between the Teff scale of red giants and models with solar calibrated mixing length disappears when considering our models and the APOGEE-Kepler stars with scaled solar metal distribution. However, a discrepancy shows up when α-enhanced stars are included in the sample. We have found that assuming mass, chemical composition and effective temperature scale of the APOGEE-Kepler catalogue, stellar models generally underpredict the change of temperature of red giants caused by α-element enhancements at fixed [Fe/H]. A second important conclusion is that the choice of the outer boundary conditions employed in model calculations is critical. Effective temperature differences (metallicity dependent) between models with solar calibrated mixing length and observations appear for some choices of the boundary conditions, but this is not a general result.

scholarly journals Accurate Masses and Radii as Test Data for Stellar Models: Status and Progress on the Copenhagen Project

1993 ◽  
Vol 137 ◽  
pp. 361-363 ◽  
Author(s):  
J. Andersen ◽  
J.V. Clausen ◽  
B.E. Helt ◽  
K.T. Johansen ◽  
B. Nordström ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Test Data ◽  
Effective Temperature ◽  
Stellar Model ◽  
The Other ◽  
Important Ingredient ◽  
Stellar Models ◽  
Test Objects ◽  
Important Test

The most important ingredient of a stellar model is its initial mass. Hence, real stars with known masses are important test objects for stellar models. Initial chemical composition is the other important starting parameter and should therefore also be known (Clausen, 1992). Finally, the most direct indicator of the evolution of a star is its radius. Together, these parameters determine the effective temperature and luminosity of the model, to be tested against a real star.

Magellanic Cloud Eclipsing Binaries: Primary Distance Indicators

1999 ◽  
Vol 190 ◽  
pp. 563-566
Author(s):  
J. D. Pritchard ◽  
W. Tobin ◽  
J. V. Clausen ◽  
E. F. Guinan ◽  
E. L. Fitzpatrick ◽  
...  
Keyword(s):  
New Zealand ◽  
Magellanic Cloud ◽  
Eclipsing Binaries ◽  
Fundamental Parameters ◽  
Distance Indicators

Our collaboration involves groups in Denmark, the U.S.A. Spain and of course New Zealand. Combining ground-based and satellite (IUEandHST) observations we aim to determine accurate and precise stellar fundamental parameters for the components of Magellanic Cloud Eclipsing Binaries as well as the distances to these systems and hence the parent galaxies themselves. This poster presents our latest progress.

scholarly journals Testing convection in stellar models using detached eclipsing binaries

2006 ◽  
Vol 2 (S239) ◽  
pp. 157-159
Author(s):  
John Southworth ◽  
Hans Bruntt
Keyword(s):  
Binary Stars ◽  
Eclipsing Binaries ◽  
Eclipsing Binary ◽  
Fundamental Properties ◽  
Eclipsing Binary Stars ◽  
Average System ◽  
Stellar Models

AbstractThe fundamental properties of detached eclipsing binary stars can be measured very accurately, which could make them important objects for constraining the treatment of convection in theoretical stellar models. However, only four or five pieces of information can be found for the average system, which is not enough. We discuss studies of more interesting and useful objects: eclipsing binaries in clusters and eclipsing binaries with pulsating components.

scholarly journals On Some Peculiar Features in the Sequences of the Old Open Star Clusters

1974 ◽  
Vol 59 ◽  
pp. 109-111
Author(s):  
A. Maeder
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Hydrogen Burning ◽  
The Core ◽  
Open Star ◽  
Solar Type ◽  
Good Agreement

In spite of the rather good agreement between the theory of stellar evolution and the observations, there exist some difficulties when one compares closely the sequences of open star clusters and the theoretical isochrones. Several, if not all, of the old open star clusters seem to be concerned, especially those which are accurately measured, namely Praesepe, NGC 2360, 752, 3680 and M67. The problem concerns the gap occuring in the HR diagram at the end of the phase of hydrogen burning in the core; it corresponds to the phase of hydrogen exhaustion (or of overall contraction). The sequence of M67 has been studied by Racine (1971) and Torres-Peimbert (1971). The well apparent gap is located farther from the zero-age main sequence than indicated by the models and the hook towards a larger Teff predicted during this phase is not observed. Differences in chemical composition may not be held responsible for these anomalies. From Torres-Peimbert's models, it may be assumed that neither solar type, nor super metal rich composition are able to reduce the discrepancies. As a further illustration, let us mention the case of NGC 752. In Table I, the main features related to the gap are examined: the disagreement, like in M67, essentially concern features 1 and 2. The observations are based on a recent study of Grenon and Mermillod (1973) and on Bell's data (1972). Bell has also mentioned the existence of discrepancies. As in M67, the gap is too far from the zero-age main sequence and does not present any sudden turning towards a larger Teff.

scholarly journals The HR Diagram

1978 ◽  
Vol 80 ◽  
pp. 101-116
Author(s):  
Jesse L. Greenstein
Keyword(s):  
Chemical Composition ◽  
Broad Band ◽  
Wavelength Region ◽  
Absolute Magnitude ◽  
Coordinate Space ◽  
Evolutionary Status ◽  
Bolometric Luminosity ◽  
The Galaxy ◽  
Stellar Masses ◽  
Hr Diagram

The HR diagram is a useful shorthand locating a star in a two-coordinate space. For the astrophysicist, the y-coordinate is bolometric luminosity, Mbol, the x-coordinate, effective temperature, Teff. Objects of given chemical composition, age (or evolutionary status) are labeled in the xy plane by mass. For an observer, y may be apparent or absolute magnitude in a certain wavelength region and x may be spectral type or color. The HR diagrams for populations differ because of age, chemical composition and stellar masses present. HR diagrams are often of mixed nature; some involve observables others derived or semi-theoretical quantities. I will display various types of HR diagrams for low-luminosity stars. For galactic or extragalactic studies the HR diagram needs a further dimension, the frequency of stars at an x,y. The mass of the Galaxy, but not its light, may be dominated by M dwarfs. HR diagrams are also interesting for their nearly empty spaces. In Fig. 1 we show as a sample, the basic results of the U.S. Naval Observatory parallax program, in which broad band (B-V) colors define the visual luminosity, My, on the main (MS) and degenerate (WD) sequences.

scholarly journals Properties of two star clusters of the LMC: NGC 2164, NGC 1850

1991 ◽  
Vol 148 ◽  
pp. 219-221
Author(s):  
A. Vallenari ◽  
C. Chiosi ◽  
G. Bertelli ◽  
G. Meylan ◽  
S. Ortolani
Keyword(s):  
Star Clusters ◽  
Theoretical Models ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Luminosity Functions ◽  
Stellar Models ◽  
Convective Overshoot

We present the photometry of two clusters NGC 2164 and NGC 1850 located in the Large Magellanic Cloud (LMC). The ages are determined taking into account the presence either of convective overshoot or of semiconvection in the stellar models. The experimental luminosity functions are compared with the theoretical models.

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