scholarly journals A Model for Contact Binary EP Andromedae

2012 ◽  
Vol 29 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Davood Manzoori
Keyword(s):  
Activity Cycle ◽  
Magnetic Activity ◽  
Close Binary ◽  
Evolutionary Status ◽  
Period Increase ◽  
System A ◽  
Contact Binary ◽  
The Times ◽  
Absolute Parameters ◽  
Program Version

AbstractThis paper presents the first comprehensive study of the EP And system, a contact binary. In this work the solution of the standard V light curve was obtained using the phoebe program (version 0.3c). Absolute parameters of the stellar components were then determined, enabling us to discuss the structure and evolutionary status of the close binary EP And. The times of minima data (‘O–C curve’) were analyzed. It was found that a third body with a period of 41.20 yr and mass 0.15 M⊙ is orbiting around the system. Also a modulating period of an 11.72-yr cycle along with a relative period increase of = 1.79 × 10−7 were obtained, which were attributed to the magnetic activity cycle and mass transfer with rate = 9.98 × 10−8 yr−1 between the components, respectively.

scholarly journals An Extensive Photometric Investigation of the W UMa System DK Cyg

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
M. M. Elkhateeb ◽  
M. I. Nouh ◽  
E. Elkholy ◽  
B. Korany
Keyword(s):  
Binary System ◽  
Evolutionary Status ◽  
Evolutionary Models ◽  
Period Increase ◽  
System A ◽  
New Period ◽  
Contact Binary ◽  
Photometric Investigation ◽  
Photometric Solution

DK Cyg (P=0.4707) is a contact binary system that undergoes complete eclipses. All the published photoelectric data have been collected and utilized to reexamine and update the period behavior of the system. A significant period increase with rate of 12.590 × 10−11 days/cycle was calculated. New period and ephemeris have been calculated for the system. A long term photometric solution study was performed and a light curve elements were calculated. We investigated the evolutionary status of the system using theoretical evolutionary models.

scholarly journals The Period Changes of YY Eridani

1998 ◽  
Vol 11 (1) ◽  
pp. 370-370
Author(s):  
C.-H. Kim ◽  
J.H. Jeong ◽  
O. Demircan ◽  
Z. Muyesseroulu ◽  
E. Budding
Keyword(s):  
Activity Cycle ◽  
Light Level ◽  
Magnetic Activity ◽  
Third Body ◽  
Period Increase ◽  
Activity Effect ◽  
Abrupt Changes ◽  
Massive Component ◽  
Photoelectric Observations

A total of eighteen times of minimum lights for YY Eri were determined from relatively new or unpublished photoelectric observations collected from Korea and Turkey. All minima available to us were intensively analyzed to deduce the character of period variation of YY Eri. It is either formed by a sinusoidal variation superimposed on an upward parabola, or a set of abrupt changes. The abrupt changes appeared to have alternatively occured in the pattern of two increases following one decrease, which may be an indication of sinusoidal variations rather than real sudden changes of period. Upward parabolic variation can be due to a secular period increase caused by mass transfer from less massive to more massive component. The sinusoidal character can arise from a third body or from a strong magnetic activity cycle. Long term sinusoidal light level variation in the light curves supports the cyclic magnetic activity effect on the orbital period. However, the third body hypothesis can not be ruled out by the present data.

scholarly journals Physical parameters of close binary systems: VIII

2021 ◽  
Author(s):  
K Gazeas ◽  
S Zola ◽  
A Liakos ◽  
B Zakrzewski ◽  
S M Rucinski ◽  
...  
Keyword(s):  
Binary Systems ◽  
Extreme Values ◽  
Close Binary ◽  
Physical Parameters ◽  
Evolutionary Status ◽  
Mass Ratio ◽  
Orbital Parameters ◽  
Contact Binaries ◽  
Contact Binary ◽  
Orbital Periods

Abstract This paper presents the results of a combined spectroscopic and photometric study of 20 contact binary systems: HV Aqr, OO Aql, FI Boo, TX Cnc, OT Cnc, EE Cet, RW Com, KR Com, V401 Cyg, V345 Gem, AK Her, V502 Oph, V566 Oph, V2612 Oph, V1363 Ori, V351 Peg, V357 Peg, Y Sex, V1123 Tau and W UMa, which was conducted in the frame of the W UMa Project. Together with 51 already covered by the project and an additional 67 in the existing literature, these systems bring the total number of contact binaries with known combined spectroscopic and photometric solutions to 138. It was found that mass, radius and luminosity of the components follow certain relations along the MS and new empirical power relations are extracted. We found that 30 per cent of the systems in the current sample show extreme values in their parameters, expressed in their mass ratio or fill-out factor. This study shows that, among the contact binary systems studied, some have an extremely low mass ratio (q<0.1) or an ultra-short orbital period (Porb <0.25 d), which are expected to show evidence of mass transfer progress. The evolutionary status of these components is discussed with the aid of correlation diagrams and their physical and orbital parameters compared to those in the entire sample of known contact binaries. The existence of very short orbital periods confirms the very slow nature of the merging process, which seems to explain why their components still exist as MS stars in contact configurations even after several Gyr of evolution.

scholarly journals A survey for variable young stars with small telescopes – III. Warm spots on the active star V1598 Cyg

2020 ◽  
Vol 497 (4) ◽  
pp. 4602-4613
Author(s):  
Dirk Froebrich ◽  
Aleks Scholz ◽  
Jochen Eislöffel ◽  
Bringfried Stecklum
Keyword(s):  
Light Curve ◽  
Broad Band ◽  
Activity Cycle ◽  
Close Binary System ◽  
Magnetic Activity ◽  
Close Binary ◽  
Low Mass Stars ◽  
Data Set ◽  
Active Star ◽  
Average Brightness

ABSTRACT Magnetic spots on low-mass stars can be traced and characterized using multiband photometric light curves. Here, we analyse an extensive data set for one active star, V1598 Cyg, a known variable K dwarf which is either pre-main sequence and/or in a close binary system. Our light curve contains 2854 photometric data points, mostly in V, Rc, Ic, but also in U, B, and Hα, with a total baseline of about 4 yr, obtained with small telescopes as part of the HOYS project. We find that V1598 Cyg is a very fast rotator with a period of 0.8246 d and varying amplitudes in all filters, best explained as a signature of strong magnetic activity and spots. We fit the photometric amplitudes in V, Rc, Ic and use them to estimate spot properties, using a grid-based method that is also propagating uncertainties. We verify the method on a partial data set with high cadence and all five broad-band filters. The method yields spot temperatures and fractional spot coverage with typical uncertainties of 100 K and 3–4  per cent, respectively. V1598 Cyg consistently exhibits spots that are a few hundred degrees warmer than the photosphere, most likely indicating that the light curve is dominated by chromospheric plage. The spot activity varies over our observing baseline, with a typical time-scale of 0.5–1 yr, which we interpret as the typical spot lifetime. Combining our light curve with archival data, we find a six year cycle in the average brightness, that is probably a sign of a magnetic activity cycle.

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 DISCOVERY OF A 1.6 YEAR MAGNETIC ACTIVITY CYCLE IN THE EXOPLANET HOST STAR ι HOROLOGII

2010 ◽  
Vol 723 (2) ◽  
pp. L213-L217 ◽  
Author(s):  
T. S. Metcalfe ◽  
S. Basu ◽  
T. J. Henry ◽  
D. R. Soderblom ◽  
P. G. Judge ◽  
...  
Keyword(s):  
Activity Cycle ◽  
Magnetic Activity

scholarly journals The Influence of Binarity on Stellar Activity

2006 ◽  
Vol 2 (S240) ◽  
pp. 442-452 ◽  
Author(s):  
Katalin Oláh
Keyword(s):  
Binary Systems ◽  
Magnetic Energy ◽  
Theoretical Calculations ◽  
Deep Convection ◽  
Magnetic Activity ◽  
Close Binary ◽  
Convective Envelope ◽  
Flux Tubes ◽  
Gravitational Forces ◽  
Magnetic Flux Tubes

AbstractActivity of late type stars is enhanced by fast rotation, which is maintained in nearly synchronized close binary systems. Magnetic activity originates in the deep convection zones of stars from where magnetic flux tubes emerge to their surfaces. The gravitational forces in binaries help the clustering of activity features giving rise to active longitudes. These preferred longitudes are observed in binaries from dwarfs to giants. Differential rotation is found in many active stars that are components of binary systems. If these binaries are circularized and nearly synchronized, then there will be a corotation latitude in their surfaces, and its position can be determined by observations and by theoretical calculations. Enhanced activity in binaries could have a reverse effect as well: strong magnetism in a binary component can modify the orbital period by the cyclic exchange of kinetic and magnetic energy in its convective envelope.

scholarly journals A Period Study of the Close Binary V508 Ophiuchi

2005 ◽  
Vol 22 (4) ◽  
pp. 311-314 ◽  
Author(s):  
Berahitdin Albayrak
Keyword(s):  
Period Change ◽  
Close Binary ◽  
Period Increase ◽  
Short Period

AbstractThe short-period (0d.34) close binary V508 Oph was observed in 2005 and four new times of minima were derived. All of the available times of minima, including the new ones, covering 69 years were analyzed. It was shown that the period change of the system is very complex. Two possible period oscillations with periods of 24.73 and 9.91 years and amplitudes of about 0.011 and 0.002 day, respectively, were found to superimpose on upward parabolic change, indicating a secular period increase at a rate of dp/dt = 4.24 × 10−9 days yr−1. The mechanisms that could explain the period changes of the system are discussed.

scholarly journals Physics of the Applegate mechanism: Eclipsing time variations from magnetic activity

2018 ◽  
Vol 620 ◽  
pp. A42 ◽  
Author(s):  
M. Völschow ◽  
D. R. G. Schleicher ◽  
R. Banerjee ◽  
J. H. M. M. Schmitt
Keyword(s):  
Binary Systems ◽  
Theoretical Work ◽  
Magnetic Activity ◽  
Close Binary ◽  
Magnetic Fluctuations ◽  
Common Envelope ◽  
Stellar Parameter ◽  
Low Mass ◽  
Time Variations ◽  
Binary Separations

Since its proposal in 1992, the Applegate mechanism has been discussed as a potential intrinsical mechanism to explain transit-timing variations in various types of close binary systems. Most analytical arguments presented so far focused on the energetic feasibility of the mechanism while applying rather crude one- or two-zone prescriptions to describe the exchange of angular momentum within the star. In this paper, we present the most detailed approach to date to describe the physics giving rise to the modulation period from kinetic and magnetic fluctuations. Assuming moderate levels of stellar parameter fluctuations, we find that the resulting binary period variations are one or two orders of magnitude lower than the observed values in RS-CVn like systems, supporting the conclusion of existing theoretical work that the Applegate mechanism may not suffice to produce the observed variations in these systems. The most promising Applegate candidates are low-mass post-common-envelope binaries with binary separations ≲1 R⊙ and secondary masses in the range of 0.30 M⊙ and 0.36 M⊙.

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