scholarly journals FK Comae and the Evolution of Close Binaries

1992 ◽  
Vol 151 ◽  
pp. 403-406
Author(s):  
David P. Huenemoerder ◽  
Lawrence W. Ramsey ◽  
Derek L. Buzasi ◽  
Harold L. Nations
Keyword(s):  
Binary Star ◽  
Magnetic Activity ◽  
Close Binary ◽  
Close Binaries ◽  
Evolutionary Status ◽  
Dynamo Theory ◽  
Cool Stars ◽  
Depth Study ◽  
Important Object ◽  
Close Binary Star

FK Com is an enigma among active cool stars. A rotationally driven magnetic dynamo is an explanation for activity. Youth and binarity are two causes of rapid rotation, but FK Com is old, single, and rotating near breakup. Much studied optical and ultraviolet data have not revealed the cause of its unusual activity. It is an important object in a more complete understanding of close binary star evolution and of the dynamo theory of magnetic activity. In 1989, we executed a coordinated ultraviolet and intensive optical spectroscopic and photometric campaign to better elucidate its characteristics. Data relevant to its evolutionary status, namely its radial velocity variations, will be discussed here, while an in depth study of the chromospheric activity will be deferred to a more detailed publication.

scholarly journals The Impact of Large Databases on the Knowledge of Late-Type Close Binaries

2004 ◽  
Vol 191 ◽  
pp. 239-246
Author(s):  
C. Maceroni
Keyword(s):  
Binary Star ◽  
Eclipsing Binaries ◽  
Close Binary ◽  
Close Binaries ◽  
Future Space ◽  
Large Databases ◽  
Interesting Object ◽  
Close Binary Star ◽  
The Impact

AbstractThis paper presents some results of the analysis of the eclipsing binaries samples that came out as by-products of the OGLE microlensing surveys. These experiments monitored millions of stars in the direction of the galactic bulge (OGLE-I), and of the Small Magellanic Cloud (OGLE-II). Their completeness allowed the discovery of rare and interesting systems. An example is a new group of long period binaries in the SMC with presumably a giant component in contact with the critical lobe, which dominates the systemic light variation (“β -contacts”). These systems obey a period-luminosity-color relation and could be used as an auxiliary, but independent, tool for distance determination. Another very interesting object, for its implications in the studies of angular momentum loss processes by magnetic braking and of stellar activity, is the system of shortest known period with M dwarf components, discovered by OGLE-I, BW3 V38, that is the target of a spectroscopic follow-up. The perspectives for close binary star research in view of future space missions, such as COROT and Eddington are briefly discussed.

scholarly journals Doppler Imaging of Stars with Roche–Geometry

2006 ◽  
Vol 2 (S240) ◽  
pp. 587-592
Author(s):  
Zs. Kővári ◽  
J. Bartus ◽  
K. Oláh ◽  
K.G. Strassmeier ◽  
J.B. Rice ◽  
...  
Keyword(s):  
Binary Star ◽  
Real Data ◽  
Doppler Imaging ◽  
Close Binary ◽  
Close Binaries ◽  
Spherical Approximation ◽  
Close Binary Star

AbstractTests are carried out on retrieving Doppler maps from distorted stars in close binaries to estimate how Doppler imaging may be aliased by ellipticity. Maps obtained for the distorted shape are compared with the results of the simple spherical approximation, using real data of the RS CVn-type close binary star ζ Andromedae.

scholarly journals The Evolution of Pre-Main Sequence Close Binaries

1980 ◽  
Vol 88 ◽  
pp. 149-153 ◽  
Author(s):  
Jon K. West ◽  
Kwan-Yu Chen
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
Total Mass ◽  
Main Sequence ◽  
Binary Star ◽  
Computer Models ◽  
Close Binary ◽  
Close Binaries ◽  
Close Binary Star ◽  
Conventional Computer

Conventional computer models of close binary star systems usually start with at least one component on the main sequence. Models of premain sequence binaries have been computed to study mass transfer (Yamasaki 1971). However no pre-main sequence computations have been published that follow the evolutionary tracks of a binary system onto the main sequence, even though some observed systems appear to be premain sequence (Field 1969). The main purpose of this investigation is the evaluation of individual close binaries with a pre-main sequence model. The evaluation will be accomplished by comparing the positions of the observed binary on the Hertzsprung-Russell diagram with the evolutionary tracks generated by the pre-main sequence model. If both components appear to have the same age and fall near the tracks of the model, then the system is possibly pre-main sequence. Eleven semidetached binaries were considered, each with a total mass between 2.5 and 6 solar masses and with a period between 0.9 and 3.4 days.

Photometric modelling of close binary star CN And

2006 ◽  
Vol 27 (1) ◽  
pp. 47-56 ◽  
Author(s):  
D. M. Z. Jassur ◽  
A. Khodadadi
Keyword(s):  
Binary Star ◽  
Close Binary ◽  
Close Binary Star

scholarly journals The Eclipses of the Close Binary Star BE UMa

1996 ◽  
Vol 158 ◽  
pp. 471-472
Author(s):  
Janet H. Wood ◽  
E. L. Robinson ◽  
E.-H. Zhang
Keyword(s):  
Light Curve ◽  
High Speed ◽  
Binary Star ◽  
Light Curves ◽  
Close Binary ◽  
Primary Star ◽  
Secondary Star ◽  
Different Depths ◽  
The Mean ◽  
Close Binary Star

BE UMa is a close binary star, not transferring mass, with an extremely hot primary star irradiating the inner face of the cool secondary star. The light curve shows a large-amplitude, sinusoidal variation with a period of 2.29 d, and an eclipse that is centered on the minimum of the variation [1], [3]. According to [1], the eclipse is partial, not total. However, it has been argued [2] that the eclipse was really flat bottomed and thus total. This has important repercussions for the deduced model of the system. To resolve this issue we obtained simultaneous UBVR photometry of BE UMa using the Stiening 4-channel, high-speed photometer on the 82-inch telescope at McDonald Observatory. The mean light curves are shown in Fig. 1. The eclipse in all colours is round bottomed and partial. The different depths are caused by the different contribution from the red secondary star in each bandpass.

scholarly journals Surface flux patterns on planets in circumbinary systems and potential for photosynthesis

2014 ◽  
Vol 14 (3) ◽  
pp. 465-478 ◽  
Author(s):  
Duncan H. Forgan ◽  
Alexander Mead ◽  
Charles S. Cockell ◽  
John A. Raven
Keyword(s):  
Binary Star ◽  
Surface Flux ◽  
Close Binary ◽  
Mass Motion ◽  
Single Star ◽  
Photosynthetic Organisms ◽  
Spatial And Temporal Distributions ◽  
Close Binary Star ◽  
Binary Star System ◽  
Circumbinary Planets

AbstractRecently, the Kepler Space Telescope has detected several planets in orbit around a close binary star system. These so-called circumbinary planets will experience non-trivial spatial and temporal distributions of radiative flux on their surfaces, with features not seen in their single-star orbiting counterparts. Earth-like circumbinary planets inhabited by photosynthetic organisms will be forced to adapt to these unusual flux patterns. We map the flux received by putative Earth-like planets (as a function of surface latitude/longitude and time) orbiting the binary star systems Kepler-16 and Kepler-47, two star systems which already boast circumbinary exoplanet detections. The longitudinal and latitudinal distribution of flux is sensitive to the centre-of-mass motion of the binary, and the relative orbital phases of the binary and planet. Total eclipses of the secondary by the primary, as well as partial eclipses of the primary by the secondary add an extra forcing term to the system. We also find that the patterns of darkness on the surface are equally unique. Beyond the planet's polar circles, the surface spends a significantly longer time in darkness than latitudes around the equator, due to the stars’ motions delaying the first sunrise of spring (or hastening the last sunset of autumn). In the case of Kepler-47, we also find a weak longitudinal dependence for darkness, but this effect tends to average out if considered over many orbits. In the light of these flux and darkness patterns, we consider and discuss the prospects and challenges for photosynthetic organisms, using terrestrial analogues as a guide.

A study of the close binary star TU Monocerotis

1968 ◽  
Vol 2 (4) ◽  
pp. 448-460
Author(s):  
Masatoshi Kitamura
Keyword(s):  
Binary Star ◽  
Close Binary ◽  
Close Binary Star

scholarly journals Asteroseismology of Close Binary Stars: Tides and Mass Transfer

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhao Guo
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Binary Systems ◽  
Binary Star ◽  
Close Binary ◽  
Close Binaries ◽  
Linear Mode ◽  
Stellar Oscillations ◽  
Theoretical Approaches ◽  
Stellar Interiors

The study of stellar oscillations allows us to infer the properties of stellar interiors. Meanwhile, fundamental parameters such as mass and radius can be obtained by studying stars in binary systems. The synergy between binarity and asteroseismology can constrain the parameter space of stellar properties and facilitate the asteroseismic inference. On the other hand, binarity also introduces additional complexities such tides and mass transfer. From an observational perspective, we briefly review the recent advances in the study of tidal effects on stellar oscillations, focusing on upper main sequence stars (F-, A-, or OB- type). The effect can be roughly divided into two categories. The first one concerns the tidally excited oscillations (TEOs) in eccentric binaries where TEOs are mostly due to resonances between dynamical tides and gravity modes of the star. TEOs appear as orbital-harmonic oscillations on top of the eccentric ellipsoidal light curve variations (the “heartbeat” feature). The second category is regarding the self-excited oscillations perturbed by static tides in circularized and synchronized close binaries. It includes the tidal deformation of the propagation cavity and its effect on eigenfrequencies, eigenfunctions, and the pulsation alignment. We list binary systems that show these two types of tidal effect and summarize the orbital and pulsation observables. We also discuss the theoretical approaches used to model these tidal oscillations and relevant complications such as non-linear mode coupling and resonance locking. Further information can be extracted from the observations of these oscillations which will improve our understanding of tides. We also discuss the effect of mass transfer, the extreme result of tides, on stellar oscillations. We bring to the readers' attention: (1) oscillating stars undergoing mass accretion (A-, F-, and OB type pulsators and white dwarfs), for which the pulsation properties may be changed significantly by accretion; (2) post-mass transfer pulsators, which have undergone a stable or unstable Roche-Lobe overflow. These pulsators have great potential in probing detailed physical processes in stellar interiors and mass transfer, as well as in studying the binary star populations.

scholarly journals Mass Transfer Characterization in Close Binary Stars

1992 ◽  
Vol 151 ◽  
pp. 337-340
Author(s):  
J. M. García ◽  
A. Giménez
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Binary Stars ◽  
Binary Star ◽  
Type System ◽  
Close Binary ◽  
Select Group ◽  
Close Binary Stars ◽  
Loss Of Mass ◽  
Close Binary Star

A method for estimating representative values of the parameters that characterize the loss of mass and angular momentum occurred during the evolution of a close binary star is considered. Absolute dimensions previous to mass-transfer stage have been obtained for a select group of 43 semidetached systems adopting a grid of values of mass loss, angular momentum loss and initial mass ratio. Our study reveals a highly non-conservative scenario for the evolution towards an Algol-type system.

Period-Activity Relations in Close Binary Systems

1983 ◽  
Vol 102 ◽  
pp. 199-202
Author(s):  
Gibor Basri ◽  
Robert Laurent ◽  
Fredrick Walter
Keyword(s):  
Magnetic Fields ◽  
Spectral Type ◽  
Binary Systems ◽  
Close Binary ◽  
Dynamo Theory ◽  
Stellar Activity ◽  
Level Of Activity ◽  
Cool Stars ◽  
Ultraviolet Observations ◽  
Extra Parameter

Since the advent of extensive ultraviolet observations of cool stars, it has been clear that the stellar activity observed is not directly correlated with the star's position on the HR diagram (Basri and Linsky 1979, Stencel et al. 1980). Observations of an important chromospheric diagnostic, the MgII resonance lines, led to the conclusion that stellar chromospheric activity had only a weak dependence on spectral type, and exhibited large variations within a given spectral type. Because of the strong observed correlation of solar activity with magnetic fields, the field is thought to be a natural candidate for the extra parameter which predicts the level of activity. Unfortunately, it is quite difficult to measure magnetic fields directly in most cool stars. Another method with which to examine correlations between magnetic field and stellar activity indirectly is the hypothesis that magnetic fluxes are directly related to a combination of the convective and rotational parameters of a star through its generation in a magnetic dynamo. The α-ω dynamo theory (Parker, 1979) predicts a direct correlation between differential rotational velocities and field generated. Durney and Robinson (1982) predict basically a linear dependence of the emergent flux on the angular velocity of the star. One might therefore expect that in stars with the same fundamental stellar parameters, the amount of activity observed would depend on the rotational velocities. This is difficult to test because most cool stars are slow rotators and only a few rotational velocities are known.

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