scholarly journals Asteroseismic tests for models of magnetically active close binaries with orbital period modulation

2002 ◽  
Vol 390 (1) ◽  
pp. 167-172 ◽  
Author(s):  
A. F. Lanza ◽  
M. Rodonò
Keyword(s):  
Orbital Period ◽  
Close Binaries

scholarly journals Cyclic Period Changes in the Algol WW Cygni

2004 ◽  
Vol 194 ◽  
pp. 87-88
Author(s):  
R. T. Zavala ◽  
B. J. McNamara ◽  
T. E. Harrison ◽  
H. Bogue ◽  
H. L. Maness
Keyword(s):  
Orbital Period ◽  
Period Change ◽  
Close Binaries ◽  
Cyclic Change ◽  
Optical Interferometer ◽  
Third Body ◽  
Magnetic Cycle ◽  
Color Changes ◽  
The Third ◽  
Algol System

AbstractYear to decade-long cyclic period changes have been observed in many classes of close binaries. The Algol binary WW Cygni shows a cyclic change in its orbital period with an amplitude of slightly more than 0.02 days and a period of 56 years. A hypothetical third or fourth body does not satisfactorily explain the observed variation in the orbital period. The change in luminosity and color of the system at primary eclipse minimum are in agreement with the model proposed by Applegate for a magnetic cycle induced period change in WW Cygni. We have commenced monitoring 9 close binaries for evidence of the luminosity and color changes consistent with the magnetic cycle hypothesis. δ Librae is suggested as a case suitable for observation with an optical interferometer to test the third body proposed for this Algol system.

A mechanism for orbital period modulation in close binaries

1992 ◽  
Vol 385 ◽  
pp. 621 ◽  
Author(s):  
James H. Applegate
Keyword(s):  
Orbital Period ◽  
Close Binaries

scholarly journals Binary frequency among the O-type stars

1979 ◽  
Vol 83 ◽  
pp. 261-264
Author(s):  
Catharine D. Garmany
Keyword(s):  
Orbital Period ◽  
Selection Effect ◽  
Close Binaries ◽  
General Question ◽  
Mass Ratio ◽  
Double Line ◽  
Mass Ratios ◽  
Low Amplitude ◽  
Different Sources ◽  
Amplitude Versus

A great deal of work has been done on the theory of mass loss and evolution in close binaries, and numerous individual systems have been discussed in this connection, but the general question of the binary frequency of O-stars, and in particular, the initial binary mass ratio frequency or distribution of secondary masses, has not been completely answered. In general, we know that about half of all O-type stars are binaries; the most recent determination by Conti, Leep and Lorre (1977) found 58% of their sample to be certain or probable binaries. However, many of these stars were judged to be variable on the basis of only a few spectra from different sources, and therefore require further study. Another point to be examined concerns the binaries with available orbits: two thirds of these are double line systems. Figure 1 shows a plot of the semi-amplitude versus orbital period for all known systems, along with some theoretical curves for different mass ratios. Not only is the lack of single line systems obvious, but low amplitude systems are almost completely missing. This would appear to be only an observational selection effect, although it is to be noted that low amplitude double line Wolf-Rayet systems have been detected. If the effect is real, it implies that O-type binaries with mass ratios (m1/m2) greater than about three do not exist.

scholarly journals Secular period decreasing of 17 detached chromospherically active binaries

2008 ◽  
Vol 4 (S252) ◽  
pp. 437-438
Author(s):  
C. Q. Luo ◽  
Y. P. Luo ◽  
X. B. Zhang ◽  
L. C. Deng ◽  
Z. Q. Luo ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Period ◽  
Close Binaries ◽  
Momentum Loss ◽  
System A ◽  
Angular Momentum Loss ◽  
Theoretical Predictions

AbstractThe long-term orbital period changes of detached chromospheric active binaries were surveyed. 17 of such systems are found to be undergoing secular period decreasing with the rates (dP/dt) of −3.05 × 10−9 to −3.77 × 10−5 days per year. The longer the orbital period, the more rapidly the period decreases. Following Stepien (1995), the period decreasing rate due to the angular momentum loss (AML) caused by magnetic wind is computed for each system. A comparison shows that the observed dP/dt's are obviously higher than that of the theoretical predictions by 1-3 orders of magnitude. It suggests that the magnetic wind is not likely the determinant mechanism driving the AML in close binaries.

scholarly journals Orbital Motion and Magnetic Activity in Close Binaries and Planetary Systems

2004 ◽  
Vol 219 ◽  
pp. 411-422
Author(s):  
Marcello Rodonò ◽  
Antonino F. Lanza
Keyword(s):  
Orbital Period ◽  
Observational Studies ◽  
Planetary Systems ◽  
Activity Cycle ◽  
Central Star ◽  
Magnetic Activity ◽  
Close Binaries ◽  
Cyclic Behaviour ◽  
Promising Tool ◽  
Cyclic Changes

The connection between orbital period variation and magnetic activity cyclic behaviour in close binaries with late-type components is addressed by discussing recent observational studies of Algols, RS CVn's, W UMa's and CVs. A theoretical model based on the Applegate's mechanism seems capable of explaining the observed orbital period modulation in terms of cyclic changes of a gravitational quadrupole moment induced by a magnetic activity cycle affecting one of the binary components. In such a case, the study of orbital period modulations offers a promising tool to investigate hydromagnetic dynamos operating in the interior of active stars, in particular, to address the fundamental question of the interaction between rotation and magnetic fields in nonlinear dynamo regimes. Moreover, interesting applications to planetary systems with a magnetically active central star are discussed.

Origin of Very-Short Orbital-Period Binary Systems

1983 ◽  
Vol 72 ◽  
pp. 263-267
Author(s):  
Shigeki Miyaji
Keyword(s):  
Binary System ◽  
Globular Cluster ◽  
Orbital Period ◽  
Binary Systems ◽  
Main Sequence ◽  
Cataclysmic Variables ◽  
Close Binaries ◽  
X Ray ◽  
Evolutionary Scenario ◽  
Orbital Periods

Recent observations of four close binaries have established that there is a group of very-short orbital-period (VSOP) binaries whose orbital periods are less than 60 minutes. The VSOP binaries consist of both x-ray close binaries (4U1626-67; Middleditch et al. 1981 and 4U1916 -0.5; White and Swank 1982) and cataclysmic variables (AM CVn; Faulkner et al. 1972 and G61-29; Nather et al. 1981). Their orbital periods are too short to have a main-sequence companion. However, four binaries, none of them belongs to any globular cluster, are too abundant to be explained by capturing mechanism of a white dwarf. Therefore it seemed to be worth to present an evolutionary scenario from an original binary system which can be applied for all of VSOP binaries.

Sign in / Sign up

Export Citation Format

Share Document