225 research outputs found
Masses and angular momenta of contact binary stars
Results are presented on component masses and system angular momenta for over
a hundred low-temperature contact binaries. It is found that the secondary
components in close binary systems are very similar in mass. Our observational
evidence strongly supports the argument that the evolutionary process goes from
near-contact binaries to A-type contact binaries, without any need of mass loss
from the system. Furthermore, the evolutionary direction of A-type into W-type
systems with a simultaneous mass and angular momentum loss is also discussed.
The opposite direction of evolution seems to be unlikely, since it requires an
increase of the total mass and the angular momentum of the system.Comment: 4 pages, 4 figures, accepted in MNRA
Angular momentum and mass evolution of contact binaries
Various scenarios of contact binary evolution have been proposed in the past,
giving hints of (sometimes contradictory) evolutionary sequence connecting
A-type and W-type systems. As the components of close detached binaries
approach each other and contact binaries are formed, following evolutionary
paths transform them into systems of two categories: A-type and W-type. The
systems evolve in a similar way but under slightly different circumstances. The
mass/energy transfer rate is different, leading to quite different evolutionary
results. An alternative scenario of evolution in contact is presented and
discussed, based on the observational data of over a hundred low-temperature
contact binaries. It results from the observed correlations among contact
binary physical and orbital parameters. Theoretical tracks are computed
assuming angular momentum loss from a system via stellar wind, accompanied by
mass transfer from an advanced evolutionary secondary to the main sequence
primary. Good agreement is seen between the tracks and the observed graphs.
Independently of details of the evolution in contact and a relation between
A-type and W-type systems, the ultimate fate of contact binaries involves the
coalescence of both components into a single fast rotating star.Comment: 11 pages, 5 figures, a short paragraph added on p. 6, MNRAS, in pres
114 Minima timings of ultra-short orbital period eclipsing binaries
We present 114 times of minima of 6 ultra-short orbital period eclipsing binaries
Photometric, Spectroscopic and Orbital Period Study of Three Early Type Semi-detached Systems: XZ Aql, UX Her and AT Peg
In this paper we present a combined photometric, spectroscopic and orbital
period study of three early-type eclipsing binary systems: XZ Aql, UX Her, and
AT Peg. As a result, we have derived the absolute parameters of their
components and, on that basis, we discuss their evolutionary states.
Furthermore, we compare their parameters with those of other binary systems and
with the theoretical models. An analysis of all available up-to-date times of
minima indicated that all three systems studied here show cyclic orbital
changes, their origin is discussed in detail. Finally, we performed a frequency
analysis for possible pulsational behavior and as a result we suggest that XZ
Aql hosts a {\delta} Scuti component.Comment: 40 pages, 16 figure
Contact binaries with additional components. III. The adaptive optics detections
We present results of the CFHT adaptive optics search for companions of a
homogeneous group of contact binary stars, as a contribution to our attempts to
prove a hypothesis that these binaries require a third star to become so close
as observed. In addition to companions directly discovered at separations of
>=1", we introduced a new method of AO image analysis utilizing distortions of
the AO diffraction ring pattern at separations of 0.07"-1". Very close
companions, with separations in the latter range were discovered in systems HV
Aqr, OO Aql, CK Boo, XY Leo, BE Scl, and RZ Tau. More distant companions were
detected in V402 Aur, AO Cam, V2082 Cyg. Our results provide a contribution to
the mounting evidence that the presence of close companions is a very common
phenomenon for very close binaries with orbital periods <1 day.Comment: Full Figs.4 and 5 are in
http://www.astro.utoronto.ca/~rucinski/Triples3
Evolution of the progenitor binary of V1309 Scorpii before merger
It was recently demonstrated that the eruption of V1309 Sco was a result of a
merger of the components of a cool contact binary. We computed a set of
evolutionary models of the detached binaries with different initial parameters
to compare it with pre-burst observations of V1309 Sco. The models are based on
our recently developed evolutionary model of the formation of cool contact
binaries. The best agreement with observations was obtained for binaries with
initial masses of 1.8-2.0 solar masses and initial periods of 2.5-3.1 d. The
evolution of these binaries consists of three phases: at first the binary is
detached and both components lose mass and angular momentum through a
magnetized wind. This takes almost two thirds of the total evolutionary
lifetime. The remaining third is spent in a semi-detached configuration of the
Algol-type, following the Roche-lobe overflow by the initially more massive
component. When the other component leaves the main sequence and moves toward
the giant branch, a contact configuration is formed for a short time, followed
by the coalescence of both components.Comment: 5 pages, 1 figure, Astronomy and Astrophysics, in prin
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