scholarly journals On the Origin of the Algol Systems

1968 ◽  
Vol 1 ◽  
pp. 396-408
Author(s):  
M. Plavec
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
List Type ◽  
Type Number ◽  
Main Sequence Stars ◽  
Maximum Light ◽  
Spectral Class ◽  
Lagrangian Surfaces ◽  
Visual Binaries

The 4th edition of the Finding List for Observers of Eclipsing Variables (Koch et al, 1963) contains 145 sufficiently well-observed eclipsing binaries brighter than 8·5m at maximum light. Among them, 59 binaries, or 41%, are systems with both components on the main sequence. The second largest group, 52 binaries or 36% of all systems, are systems similar to Algol. These can be characterized as follows: (1)The primary (more massive) components are main-sequence stars, fitting well into the mass-luminosity relation defined by visual binaries and by eclipsing binaries with both components on the main sequence (detached systems).(2)The secondary components are of later spectral type than the primaries, and can be best characterized as subgiants. They are overluminous for their mass as well as for their spectral class.(3)As a rule, the secondary components fill their respective critical Roche lobes (innermost Lagrangian surfaces).

scholarly journals On the Accuracy of Spectral Classifications of Main-Sequence Stars

1973 ◽  
Vol 50 ◽  
pp. 52-59
Author(s):  
W. Gliese
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Standard Errors ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Spectral Class ◽  
Classification Errors ◽  
Nearby Stars

By examining the observed dispersion in (colour, spectral type) relations, classification errors have been derived from the data of nearby stars. The comparisons of the colour deviations observed in spectral regions of large variations of colour with type with the deviations in regions of small variations give the following standard errors in units of a tenth of a spectral class: For K dwarfs ±0.6 (MK), ±1.2 (Mt. Wilson), ±0.7 (Kuiper); for early M dwarfs ±0.9: (MK), ±0.7 (Mt. Wilson), ±0.5: (Kuiper); and for late M dwarfs ±0.7 (Kuiper).

scholarly journals The Rotation of the Main-Sequence Components of Algol-Type Semi-Detached Eclipsing Binaries

1970 ◽  
Vol 4 ◽  
pp. 178-186
Author(s):  
E.P.J. Van Den Heuvel
Keyword(s):  
Spectral Type ◽  
Spectral Region ◽  
Main Sequence ◽  
Rotational Velocity ◽  
Eclipsing Binaries ◽  
Main Sequence Stars ◽  
Sequence Components ◽  
Tentative Explanation ◽  
Region Ii ◽  
Existing Data

AbstractNewly determined rotational velocities of the main-sequence components of 14 Algol-type semi-detached systems and of 2 detached systems are presented. Combination of these data with the existing data on the rotation of the components of semi-detached systems shows that (i) in systems with primaries of spectral type B8 or later and with P<5 days, deviations from synchronism between rotation and revolution are small in 14 out of 15 cases. The average rotational velocity of the primaries in such systems is 75 km/sec, viz. only 40% of the average rotational velocity of single main-sequence stars in the same spectral region: (ii) primaries of spectral type earlier than B8 in systems with short as well as long periods tend to rotate more than twice as fast as one would expect from synchronism. A tentative explanation for these results is presented.

scholarly journals Discussion

1957 ◽  
Vol 3 ◽  
pp. 173-174
Keyword(s):  
Binary Systems ◽  
Classification Scheme ◽  
Eclipsing Binaries ◽  
Emission Lines ◽  
Velocity Variation ◽  
List Type ◽  
Type Number ◽  
Simple Manner ◽  
Gas Streams ◽  
Spectral Class

Following the papers on instability in binary systems, Dr S. Gaposchkin described a classification scheme that he had devised to describe the eclipsing binaries having emission lines, gas streams, or thick atmospheres. Such stars Gaposchkin calls the ‘camouflaged eclipsing variables’, and divides them into five groups: (1)Typical members are UX Mon and SX Cas: the spectral type of the brighter star is B or A, that of the fainter is G or later. The minima are of equal depth. Balmer emission is present.(2)Prototypes are β Lyr and ν Sgr: only one component can be seen distinctly, but two minima are present in the light curve. The spectroscopic behaviour is most complicated.(3)Prototypes are RT And and YY Gem: the spectral class is G or later. Ca 11 emission is present. The depths of the minima are roughly equal, and the dimensions of the components are about the same.(4)The prototype is DN Ori: both components are so well camouflaged that no definite velocity variation has been observed.(5)Prototypes are V444 Cyg or UX UMa: the bright lines are strong, and their displacements and intensities do not vary in a simple manner with phase.

scholarly journals CzeV1731: The unique doubly eclipsing quadruple system

2020 ◽  
Vol 642 ◽  
pp. A63
Author(s):  
P. Zasche ◽  
Z. Henzl ◽  
H. Lehmann ◽  
J. Pepper ◽  
B. P. Powell ◽  
...  
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Main Sequence Stars ◽  
The Third ◽  
System A ◽  
Promising Target ◽  
Quadruple System ◽  
The Masses ◽  
Double Twin

We report the discovery of the relatively bright (V = 10.5 mag), doubly eclipsing 2+2 quadruple system CzeV1731. This is the third known system of its kind, in which the masses are determined for all four stars and both the inner and outer orbits are characterized. The inner eclipsing binaries are well-detached systems moving on circular orbits: pair A with period PA = 4.10843 d and pair B with PB = 4.67552 d. The inner binaries contain very similar components (q  ≈  1.0), making the whole system a so-called double twin. The stars in pair B have slightly larger luminosities and masses and pair A shows deeper eclipses. All four components are main-sequence stars of F/G spectral type. The mutual orbit of the two pairs around the system barycenter has a period of about 34 yr and an eccentricity of about 0.38. However, further observations are needed to reveal the overall architecture of the whole system, including the mutual inclinations of all orbits. This is a promising target for interferometry to detect the double at about 59 mas and ΔMbol <  1 mag.

scholarly journals Stellar 5 min Oscillations

1983 ◽  
Vol 66 ◽  
pp. 469-486
Author(s):  
Jørgen Christensen-Dalsgaard ◽  
Søren Frandsen
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Total Flux ◽  
The Sun ◽  
Major Fraction ◽  
Main Sequence Stars ◽  
Red Supergiants

AbstractEstimates are given for the amplitudes of stochastically excited oscillations in Main Sequence stars and cool giants; these were obtained using the equipartition between convective and pulsational energy which was originally proposed by Goldreich and Keeley. The amplitudes of both velocity and luminosity perturbation generally increase with increasing mass along the Main Sequence as long as convection transports a major fraction of the total flux, and the amplitudes also increase with the age of the model. The 1.5 Mʘ ZAMS model, of spectral type F0, has velocity amplitudes ten times larger than those found in the Sun. For very luminous red supergiants luminosity amplitudes of up to about 0ṃ.1 are predicted, in rough agreement with observations presented by Maeder.

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.

A Discussion on astronomy in the ultraviolet - The ultraviolet spectrum of B-type supergiants

1975 ◽  
Vol 279 (1289) ◽  
pp. 429-442
Keyword(s):  
High Resolution ◽  
Spectral Type ◽  
Main Sequence ◽  
Ultraviolet Spectrum ◽  
Absorption Lines ◽  
Light Elements ◽  
Main Sequence Stars ◽  
Complete Identification ◽  
Constant Strength

The broad, steep-sided absorption lines in B-type supergiant spectra are stronger than the absorption lines in main-sequence stars. In addition to lines from the second, third and fourth spectra of the light elements and the metals there is a broad, pointed feature at 1720 A which has constant strength in the B-type supergiants regardless of spectral type. The complete identification of this blend is not known. At high resolution the ultraviolet resonance lines of C iv, N v, Si hi and Si iv in the spectra of OB supergiants are shortward displaced by velocities up to 1800 km s-1 indicating the presence of an escaping atmosphere. At type B5 the expanding atmosphere is moving at about 120 km s-1 which means that the material is probably brought to rest before it escapes from the star. Evidence is presented of the presence of a stationary shell around the B5Ia supergiant q Canis Majoris as well as a slowly expanding atmosphere.

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.

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