Rediscussion of eclipsing binaries. XV - Alpha Coronae Borealis, a main-sequence system with components of types A and G

1986 ◽  
Vol 91 ◽  
pp. 1428 ◽  
Author(s):  
J. Tomkin ◽  
D. M. Popper
Keyword(s):  
Main Sequence ◽  
Eclipsing Binaries

scholarly journals A Search for Main-Sequence Binaries in Globular Clusters

1980 ◽  
Vol 85 ◽  
pp. 357-359 ◽  
Author(s):  
Martha H. Liller
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Cluster Center ◽  
Distance Modulus ◽  
List Type ◽  
Galactic Latitude ◽  
Plate Material ◽  
Evolved Stars ◽  
Visual Distance

It is becoming increasingly clear that no (or only one or two) binaries occur among the evolved stars in globular clusters. Therefore, if binaries exist at all in these systems, they must be found on or near the main sequence. I have chosen 6 clusters to search for faint eclipsing binaries by the following criteria: (1)the apparent visual distance modulus (Harris 1976) (m-M)V ≤ 14.5 mag;(2)the Peterson and King (1975) concentration class c ≤ 1.5, so that the search can be conducted near or at the cluster center where binaries would most likely be found; and(3)the galactic latitude is sufficiently large to avoid problems of extreme contamination by field stars. The clusters thus chosen are NGC3201, 5139 (Omega Cen), 6121 (M4), 6218 (M12), 6254 (M10), and 6809 (M55). The plate material obtained on three nights with the 4-m telescope at CTIO in 1979, consists of seven to nine plates of each cluster on IIIa-F emulsion with an RG610 filter; the search is being conducted with a blink microscope.

scholarly journals Apsidal motion in evolved binary systems

1984 ◽  
Vol 105 ◽  
pp. 419-420
Author(s):  
Alvaro Giménez
Keyword(s):  
Preliminary Report ◽  
Binary Systems ◽  
Main Sequence ◽  
Review Paper ◽  
Theoretical Models ◽  
Eclipsing Binaries ◽  
Apsidal Motion ◽  
Different Sources ◽  
Obvious Extension ◽  
Good Agreement

The study of apsidal motions in eclipsing binaries has proven to be one of the best methods to check the internal density concentrations of the stars predicted by theoretical models. During the main sequence phase, we have found a good agreement between the observed apsidal motion rates and computer-constructed stellar models provided that a realistic consideration is made of the evolution between the lower and upper borders of the main sequence (Giménez and García-Pelayo, 1982). An obvious extension of this work is a throughout study of the more evolved evolved systems beyond the TAMS where theoretical models are less accurate and empirical data from different sources are largely needed (see review paper by Zahn in this volume). A preliminary report on such a study is presented.

Absolute parameters of three southern eclipsing binaries: DQ Car, BK Ind, and V4396 Sgr

2020 ◽  
Vol 493 (2) ◽  
pp. 2659-2675
Author(s):  
Derya Sürgit ◽  
Ahmet Erdem ◽  
Chris A Engelbrecht ◽  
Fred Marang
Keyword(s):  
South African ◽  
Binary Stars ◽  
Main Sequence ◽  
Interstellar Extinction ◽  
Eclipsing Binaries ◽  
Evolutionary Status ◽  
Distance Modulus ◽  
Main Sequence Stars ◽  
The Masses ◽  
Absolute Parameters

ABSTRACT We present combined photometric and spectroscopic analyses of the three southern eclipsing binary stars: DQ Car, BK Ind, and V4396 Sgr. Radial velocity curves of these three systems were obtained at the South African Astronomical Observatory, and their light curves from the available data bases and surveys were used for the analysis. 75 new times of minima for these three eclipsing binaries were derived, and their ephemerides were updated. Only the O–C diagram of DQ Car indicates a cyclical variation, which was interpreted in terms of the light-time effect due to a third body in the system. Our final models describe these three systems as Algol-like binary stars with detached configurations. The masses and radii were found to be M1 = 1.86(±0.17) M⊙, R1 = 1.63(±0.06) R⊙ and M2 = 1.74(±0.17) M⊙, R2 = 1.52(±0.07) R⊙ for the primary and secondary components of DQ Car; M1 = 1.16(±0.05) M⊙, R1 = 1.33(±0.03) R⊙ and M2 = 0.98(±0.04) M⊙, R2 = 1.00(±0.03) R⊙ for BK Ind; and M1 = 3.14(±0.22) M⊙, R1 = 3.00(±0.09) R⊙ and M2 = 3.13(±0.24) M⊙, R2 = 2.40(±0.08) R⊙ for V4396 Sgr, respectively. The distances to DQ Car, BK Ind, and V4396 Sgr were derived to be 701(±50), 285(±20), and 414(±30) pc from the distance modulus formula, taking into account interstellar extinction. The evolutionary status of these three systems was also studied. It has been found that the components of DQ Car are very young stars at the age of ∼25 Myr and those of BK Ind and V4396 Sgr are evolved main-sequence stars at the ages of ∼2.69 Gyr and ∼204 Myr, respectively.

scholarly journals Eclipsing binary stars as tests of stellar evolutionary models and stellar ages

2008 ◽  
Vol 4 (S258) ◽  
pp. 161-170 ◽  
Author(s):  
Keivan G. Stassun ◽  
Leslie Hebb ◽  
Mercedes López-Morales ◽  
Andrej Prša
Keyword(s):  
Binary Stars ◽  
Main Sequence ◽  
Magnetic Activity ◽  
Eclipsing Binaries ◽  
Evolutionary Models ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
Eclipsing Binary Stars ◽  
Sequence Components ◽  
Low Mass

AbstractEclipsing binary stars provide highly accurate measurements of the fundamental physical properties of stars. They therefore serve as stringent tests of the predictions of evolutionary models upon which most stellar age determinations are based. Models generally perform very well in predicting coeval ages for eclipsing binaries with main-sequence components more massive than ≈1.2 M⊙; relative ages are good to ~5% or better in this mass regime. Low-mass main-sequence stars (M < 0.8 M⊙) reveal large discrepancies in the model predicted ages, primarily due to magnetic activity in the observed stars that appears to inhibit convection and likely causes the radii to be 10–20% larger than predicted. In mass-radius diagrams these stars thus appear 50–90% older or younger than they really are. Aside from these activity-related effects, low-mass pre–main-sequence stars at ages ~1 Myr can also show non-coevality of ~30% due to star formation effects, however these effects are largely erased after ~10 Myr.

Variable Star Identification in the BATC Field of M67

2005 ◽  
Vol 277-279 ◽  
pp. 869-875
Author(s):  
Hwihyun Kim ◽  
Yong Ik Byun
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Variable Star ◽  
Open Cluster ◽  
Open Clusters ◽  
Eclipsing Binaries ◽  
Photometric Variability ◽  
Phase Dispersion ◽  
Star Identification

We present the result of photometric variability investigation for stars in the field of M67. The old open cluster M67, one of the most studied open clusters, shows the sign of significant main-sequence binary population in its color-magnitude diagrams. Identification of eclipsing binaries and follow-up studies will enable us to study the nature of binary population in most direct manner. We used approximately 350 images from the BATC (Beijing-Arizona-Taipei-Connecticut) data archive to examine variability within one square degree field centered on M67. A total of 18 stars were classified to be real variables. Our new discoveries include seven eclipsing binary systems of which two are likely to be W UMa systems. All of these variables were found using the phase dispersion minimization (PDM) method developed by Shin and Byun[11].

scholarly journals Time-Resolved Spectroscopy of Short Period RS CVn Systems

1993 ◽  
Vol 137 ◽  
pp. 392-394
Author(s):  
C. Lázaro ◽  
M.J. Arévalo
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Time Resolved ◽  
Binary Model ◽  
Short Period ◽  
First Results ◽  
Orbital Phase ◽  
Phase Resolution ◽  
Orbital Periods

AbstractWe have initiated a programme of spectroscopic observations of RS CVn short-period group, with orbital phase resolution. The systems of this group are all eclipsing binaries with both components at the Main Sequence, and most of them have similar spectral type components. The high rotational velocities and their short orbital periods (less than 1 day) hinder the spectroscopic study of these stars. We presents the first results yielded by Hα line observations of the systems XY UMa and WY Cnc. Both systems were observed during 1991 with reasonably wide orbital phase coverage. The analysis of the spectra is made by comparison with a binary model, constructed from the observed spectra of normal stars of the same spectral type as the RS CVn system components. The model accounts for the partial contribution of each component at any orbital phase within eclipses.

scholarly journals Modelling Early-type Stars in Eclipsing Binaries of Open Clusters: A New Method for Age Determination from the Ratio of Radii

2011 ◽  
Vol 28 (1) ◽  
pp. 66-76 ◽  
Author(s):  
M. Yıldız
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Age Determination ◽  
Primary Component ◽  
Open Clusters ◽  
Eclipsing Binaries ◽  
Primary Star ◽  
Fundamental Properties ◽  
Sources Of Knowledge ◽  
The Difference

AbstractBinary systems, in particular eclipsing binaries, are essential sources of knowledge of the fundamental properties of stars. The ages of binaries, members of open clusters, are constrained by their own fundamental properties and by those of the hosting cluster. The ages of eleven open clusters are here found by constructing models for the components of twelve eclipsing binaries. The difference between the ages we find and the ages of the clusters derived from isochrone fitting is up to 40%. For the binary system V497 Cep in NGC 7160, the difference is about 100%. Binary systems whose primary component is about to complete its main-sequence lifetime, such as V453 Cyg and V906 Sco, are the most suitable systems for age determination. Using model results for these stars, we derive an expression for sensitive and uncomplicated relative age determination of binary systems (age divided by the main-sequence lifetime of the primary star). The expression is given as a logarithm of radii ratio divided by a logarithm of mass ratio. Two advantages of this expression are that: (i) it is nearly independent of the assumed chemical composition of the models because of the appearance of the ratio of radii; and (ii) the ratios of radii and masses are observationally much more precise than their absolute values. We also derive another expression using luminosities rather than radii and compare results.

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