scholarly journals Contact Binary Stars

1983 ◽  
Vol 71 ◽  
pp. 447-461 ◽  
Author(s):  
A.K. Dupree
Keyword(s):  
Binary Stars ◽  
Rotational Velocity ◽  
Type Systems ◽  
Ultraviolet Emission ◽  
X Ray ◽  
Contact Binary Stars ◽  
Contact Binary ◽  
Turn Over

Abstract:Ultraviolet and X-ray surveys of the W Ursae Majoris type stars are reviewed. These systems exhibit extended coronas and transition regions that are confined close to the optically determined surfaces. Correlations of X-ray activity with period or rotational velocity indicate a turn-over or saturation of emission at the short periods or high velocities found in the W UMa-type systems. For a number of systems, ultraviolet emission appears to be anti-correlated with the strength of X-ray emission. These observations are discussed in terms of solar structures, activity, and evolution.

Contact binary stars. I - an X-ray survey

1984 ◽  
Vol 277 ◽  
pp. 263 ◽  
Author(s):  
R. G. Cruddace ◽  
A. K. Dupree
Keyword(s):  
Binary Stars ◽  
X Ray ◽  
Contact Binary Stars ◽  
Contact Binary

scholarly journals W Ursae Majoris Star Models: Observational Constraints

1988 ◽  
Vol 108 ◽  
pp. 213-214
Author(s):  
Albert P. Linnell
Keyword(s):  
Binary Stars ◽  
Relaxation Oscillation ◽  
Thermal Relaxation ◽  
Type Systems ◽  
Light Curves ◽  
Primary Minimum ◽  
Star Models ◽  
Massive Component ◽  
Contact Binary Stars ◽  
Contact Binary

W Ursae Majoris stars can be understood as contact binary stars with a common envelope (Lucy 1968). They subdivide into two types: The A-type are earlier inspectral class than about F5, are believed to have radiative envelopes, and associate primary (deeper) eclipse minimum with transit eclipse. The W-type have spectral classes later than F5, are believed to have convectlve envelopes, and associate primary minimum with occultation eclipse. Controversy has surrounded the explanation of W-type light curves.Four distinct models have been introduced to describe the envelopes or photospheres of W UMa stars. (1) The Rucinski hot secondary model directly explains W-type light curves on a postulational basis. Since 70%-90% of the emitted radiation from the secondary (less massive) component is believed to reach the secondary via circulation currents from the primary, there is an apparent thermodynamic mystery why the secondary should be hotter. (2) The Lucy Thermal Relaxation Oscillation (TRO) model argues that the secondary component is perpetually out of thermal equilibrium and that the components are in contact only during part of a given TRO cycle. During contact the photosphere is supposed to be barotropic. In this case primary minimum always associates with transit eclipse, in disagreement with observation for W-type systems. (3) The Shu et al. thermal discontinuity (DSC) model also argues for a barotropic photosphere but differs from Lucy on the gravity brightening exponent. The changes are insufficient to produce W-type light curves, (4) Webbink (1977), and, separately, Nariai (1976), argue for a baroclinic envelope. If the baroclinicity extends to the photosphere there is a possibility that W-type l i g h t curves could be explained. In particular, the Webbink scenario produces a hot secondary.

scholarly journals Structure and evolution of W UMa-type systems

2008 ◽  
Vol 4 (S252) ◽  
pp. 423-424 ◽  
Author(s):  
Lifang Li ◽  
Fenghui Zhang ◽  
Zhanwen Han ◽  
Dengkai Jiang ◽  
Tianyu Jiang
Keyword(s):  
Binary Stars ◽  
Type Systems ◽  
Magnetic Activity ◽  
Activity Level ◽  
Average Lifetime ◽  
Type Contact ◽  
Contact Binaries ◽  
Contact Binary Stars ◽  
Contact Binary ◽  
Low Mass

AbstractWe summarize and discuss our recent works on the structure and evolution of low-mass W UMa-type contact binary stars. Three conclusions are given as followings: (1) The energy transfer is taken place in the radiative region of common envelope of W UMa systems; (2) The magnetic activity level of W UMa systems is weaker than that of non-contact binaries or rapid-rotating single stars; (3) The evolutionary outcome of W UMa systems might be the rapid-rotating single stars, and an average lifetime is derived to be about 7 Gyr for W UMa systems.

scholarly journals On the properties of contact binary stars

2004 ◽  
Vol 426 (3) ◽  
pp. 1001-1005 ◽  
Author(s):  
Sz. Csizmadia ◽  
P. Klagyivik
Keyword(s):  
Binary Stars ◽  
Contact Binary Stars ◽  
Contact Binary

scholarly journals A Cyclic Thermal Instability in Contact Binary Stars

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.

scholarly journals Origin of the orbital period change in contact binary stars

2019 ◽  
Vol 28 (06) ◽  
pp. 1950044 ◽  
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.

The evolutionary state of contact and near-contact binary stars

1988 ◽  
Vol 231 (2) ◽  
pp. 341-352 ◽  
Author(s):  
R. W. Hilditch ◽  
D. J. King ◽  
T. M. McFarlane
Keyword(s):  
Binary Stars ◽  
Evolutionary State ◽  
Contact Binary Stars ◽  
Contact Binary

scholarly journals AROSATSurvey of Contact Binary Stars

2006 ◽  
Vol 131 (1) ◽  
pp. 633-637 ◽  
Author(s):  
M. T. Geske ◽  
S. J. Gettel ◽  
T. A. McKay
Keyword(s):  
Binary Stars ◽  
Contact Binary Stars ◽  
Contact Binary
Sign in / Sign up

Export Citation Format

Share Document