Relative Luminosity and Surface Brightness of the Components of Contact Binary Stars

Contact binary stars of the W UMa-type (also known as W) are unique objects: The luminosity, produced almost exclusively in the more massive component is efficiently distributed through the common envelope so that the surface brightness is practically identical over the whole visible surface of the binary. Mass ratios are known to span the whole wide range, from almost unity to very small values, as small as q = 0.066. Typically, the primary component provides the luminosity, while both components provide the radiating area. The range of the primary masses is moderate and corresponds to Main Sequence spectral types from middle A to early K and roughly maps into the orbital-period range of about 1.5 days to 0.22 days.

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Observational Evidence for the Evolution of Contact Binary Stars

Interacting Binaries ◽

10.1007/978-94-009-5337-6_3 ◽

1985 ◽

pp. 51-82 ◽

Cited By ~ 9

Author(s):

Stefan W. Mochnacki

Keyword(s):

Binary Stars ◽

Observational Evidence ◽

Contact Binary Stars ◽

Contact Binary

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On the properties of contact binary stars

Astronomy and Astrophysics ◽

10.1051/0004-6361:20040430 ◽

2004 ◽

Vol 426 (3) ◽

pp. 1001-1005 ◽

Cited By ~ 52

Author(s):

Sz. Csizmadia ◽

P. Klagyivik

Keyword(s):

Binary Stars ◽

Contact Binary Stars ◽

Contact Binary

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A Cyclic Thermal Instability in Contact Binary Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900012158 ◽

1976 ◽

Vol 73 ◽

pp. 331-331

Author(s):

Brian P. Flannery

Keyword(s):

Mass Exchange ◽

Binary Stars ◽

Thermal Evolution ◽

Normal Population ◽

Equal Mass ◽

General Nature ◽

Convective Envelope ◽

Short Period ◽

Contact Binary Stars ◽

Contact Binary

Contact binary stars coupled by a common convective envelope in which the entropy is constant, the Lucy model, are unstable against mass exchange: if either component begins to transfer mass, it will continue to do so. A detailed sequence of models is calculated which follows the thermal evolution of a 2M⊙ contact binary of normal Population I abundances (X=0.70, Z = 0.02), starting at nearly equal mass. The initial instability develops into a cyclic mass-exchange with the mass fraction oscillating between 0.56≤m2/(m1 + m2)≤0.62 with a period of ~107yr. Throughout the cycle the component stars are not in thermal equilibrium. The instability is of a general nature, and such oscillating systems can satisfactorily populate the short period, red region of the period color relation for WUMa stars.

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Origin of the orbital period change in contact binary stars

International Journal of Modern Physics E ◽

10.1142/s0218301319500447 ◽

2019 ◽

Vol 28 (06) ◽

pp. 1950044 ◽

Cited By ~ 1

Author(s):

V. V. Sargsyan ◽

H. Lenske ◽

G. G. Adamian ◽

N. V. Antonenko

Keyword(s):

Orbital Period ◽

Binary Stars ◽

Binary Systems ◽

Binary Star ◽

Period Change ◽

Mass Asymmetry ◽

Contact Binary Stars ◽

Contact Binary ◽

Energy Formula ◽

Orbital Periods

The evolution of contact binary star systems in mass asymmetry (transfer) coordinate is considered. The orbital period changes are explained by an evolution in mass asymmetry towards the symmetry (symmetrization of binary system). It is predicted that decreasing and increasing orbital periods are related, respectively, with the nonoverlapping and overlapping stage of the binary star during its symmetrization. A huge amount of energy [Formula: see text][Formula: see text]J is converted from the potential energy into internal energy of the stars during the symmetrization. As shown, the merger of stars in the binary systems, including KIC 9832227, is energetically an unfavorable process. The sensitivity of the calculated results to the values of total mass and orbital angular momentum is analyzed.

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