scholarly journals W UMa Stars and Angular Momentum Loss

1980 ◽  
Vol 88 ◽  
pp. 491-494 ◽  
Author(s):  
Osmi Vilhu ◽  
Timo Rahunen
Keyword(s):  
Time Scale ◽  
Type Systems ◽  
Light Curves ◽  
Theoretical Studies ◽  
Mass Ratio ◽  
Subsequent Evolution ◽  
Convective Envelope ◽  
Angular Momentum Loss ◽  
Envelope Model ◽  
The Common

The structure and evolution of W UMa stars is still unsolved although considerable progress has been achieved in recent years. Most theoretical studies are based on the common convective envelope model by Lucy (1968a,b), which almost satisfactorily explains the nearly equal minima of the light curves. All A-type (Wilson, 1978) and some W-type systems (Whelan et al., 1979) may contain an evolved primary. In this case stable models exist (Hazlehurst, 1970; Moss and Whelan, 1970). Computations performed for the subsequent evolution (Moss, 1971; Hazlehurst and Meyer-Hofmeister, 1973; Rahunen and Vilhu, 1977) show nuclear time scale evolution towards more extreme mass ratio, supplemented by possible thermal time scale oscillations.

scholarly journals A Study on W Ursae Majoris-Type Systems Recognised by the ROTSE-IIId Experiment

2013 ◽  
Vol 30 ◽  
Author(s):  
D. Çoker ◽  
S. Özdemir ◽  
C. Yeşilyaprak ◽  
S. K. Yerli ◽  
N. Aksaker ◽  
...  
Keyword(s):  
Type Systems ◽  
Light Curves ◽  
Geometrical Parameters ◽  
Mass Ratio ◽  
Orbital Inclination ◽  
Fourier Decomposition ◽  
Search Experiment ◽  
Orbital Periods ◽  
The Fourier Transform ◽  
Optical Transient

AbstractWe present a study on characterising the light curves of W UMa-type systems gathered from the archive containing 5 years of data observed with the Robotic Optical Transient Search Experiment Telescope (ROTSE-IIId) located in Turkey. A sample of 45 W UMa-type systems was studied on the basis of Fourier decomposition of light curves and some basic geometrical parameters, namely degree of contact (f), mass ratio (q), and orbital inclination (i), as approximated values for these systems were determined. Moreover, methods based on the Fourier transform technique were applied to the discrete data to determine the orbital periods of those systems. Preliminary estimates for the system parameters were presented and compared with the values available in the literature.

CSS J075415.6+191052 and NW Leo: two contact binaries at different evolutionary stages

2021 ◽  
Author(s):  
Xu-Dong Zhang ◽  
Shengbang Qian ◽  
Ergang Zhao ◽  
Qijun Zhi ◽  
Aijun Dong ◽  
...  
Keyword(s):  
Relaxation Oscillation ◽  
Thermal Relaxation ◽  
Light Curves ◽  
Secondary Component ◽  
High Mass ◽  
Dark Spot ◽  
Left Shoulder ◽  
Mass Ratio ◽  
Convective Envelope ◽  
Contact Binary

Abstract Multi-color light curves of CSS J075415.6+191052 and NW Leo are presented and the photometric solutions suggest that CSS J075415.6+191052 is a low mass ratio (q=0.178) and slightly deep contact binary (f=34.9%), while NW Leo with high mass ratio (q=0.707) and shallow degree of contact (f=2.3%). For CSS J075415.6+191052, the RI light curves show weakening around the left shoulder of secondary minimum, which indicates that there may be a dark spot on the secondary component. However, the light curves of BV bands are totally symmetric. It is unreasonable if the dark spot is caused by magnetic activity or mass transfers between two components. Therefore, the weakening of the light curves in this contact binary is caused by something else. A possible explanation is mass transferring from primary component to common convective envelope through the inner Lagrangian point, and this part of the mass, for some reason, weakens RI bands of light from secondary component. O - C analysis of NW Leo reveals a cyclic period change with a modulation period of 4.7 years, which may be caused by the light travel time effect of a third body. The positions of CSS J075415.6+191052 and NW Leo in P - J_{orb}' diagram suggest that the former is more evolved, which is in agreement with their photometric solutions. In the current stage, CSS J075415.6+191052 is dominated by the angular momentum loss theory, but NW Leo mainly follow the thermal relaxation oscillation theory.

scholarly journals Evolutionary scenario for W UMa-type stars

2008 ◽  
Vol 4 (S252) ◽  
pp. 427-428 ◽  
Author(s):  
K. Stepień ◽  
K. Gazeas
Keyword(s):  
Thermal Equilibrium ◽  
Large Scale ◽  
Primary Component ◽  
Mass Ratio ◽  
Common Envelope ◽  
Evolutionary Scenario ◽  
Angular Momentum Loss ◽  
Temperature Equalization ◽  
The Common ◽  
Large Scale Flow

AbstractAn alternative to TRO model of a W UMa-type star is presented in which the binary is past mass exchange with mass ratio reversal. The secondary is hydrogen depleted and both components are in thermal equilibrium. Evolution in contact is driven by orbital angular momentum loss and mass transfer from the secondary to primary component, similarly as it is observed in Algols. Temperature equalization of both components results from an assumed energy transfer by a large scale flow encircling the whole system in the common envelope.

scholarly journals Defining Characteristics of Fast Novae

1979 ◽  
Vol 53 ◽  
pp. 532-532
Author(s):  
James W. Truran
Keyword(s):  
Light Curves ◽  
Theoretical Studies ◽  
Hydrogen Fuel ◽  
Core Mass ◽  
Infrared Observations ◽  
Bolometric Luminosity ◽  
Thermonuclear Burning ◽  
Residual Hydrogen ◽  
The Common ◽  
Nova Outburst

Scrutiny of the light curves of the common novae yields important clues concerning both the nature of the nova outburst and the characteristics of the underlying white dwarfs. Ultraviolet and infrared observations have served to make available essentially complete bolometric light curves for several recent novae. These data confirm our earlier prediction that, following maximum, both fast and slow novae experience an epoch (of varying duration) of substantially hydrostatic evolution defined by thermonuclear burning of the residual hydrogen fuel at constant bolometric luminosity. Theoretical studies reveal that the luminosity during this phase of a nova’s evolution is well represented by the Paczynski core mass-luminosity relation for such shell burning configurations involving degenerate stellar cores. This luminosity represents, as well, an increasingly significant fraction of the Eddington luminosity with increasing white dwarf mass.

scholarly journals New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions

2020 ◽  
Vol 29 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Fatemeh Davoudi ◽  
Atila Poro ◽  
Fahri Alicavus ◽  
Afshin Halavati ◽  
Saeed Doostmohammadi ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Mass Function ◽  
Light Curves ◽  
Complete Analysis ◽  
Physical Parameters ◽  
Mass Ratio ◽  
Third Body ◽  
Eclipsing Binary

AbstractNew observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m3) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.

scholarly journals Fast Comparison of High-Precision Time Scales Using GNSS Receivers

2017 ◽  
Vol 2017 ◽  
pp. 1-4
Author(s):  
Vojtech Vigner ◽  
Jaroslav Roztocil
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
High Performance ◽  
Data Format ◽  
Common View ◽  
Log Files ◽  
Gnss Receivers ◽  
Precision Time ◽  
The Common ◽  
The Difference

Comparison of high-performance time scales generated by atomic clocks in laboratories of time and frequency metrology is usually performed by means of the Common View method. Laboratories are equipped with specialized GNSS receivers which measure the difference between a local time scale and a time scale of the selected satellite. Every receiver generates log files in CGGTTS data format to record measured differences. In order to calculate time differences recorded by two receivers, it is necessary to obtain these logs from both receivers and process them. This paper deals with automation and speeding up of these processes.

scholarly journals CCD Observations and Analysis of the W UMA Type Binary SS Arietis

1998 ◽  
Vol 11 (1) ◽  
pp. 382-382
Author(s):  
Wonyong Han ◽  
Chun-Hwey Kim ◽  
Jae Woo Lee ◽  
Ho-Il Kim ◽  
Woo-Baik Lee
Keyword(s):  
Period Change ◽  
Light Curves ◽  
Period Variation ◽  
Light Elements ◽  
Astronomy Observatory ◽  
Third Body ◽  
Convective Envelope ◽  
Ccd Observations ◽  
The Times

The BVR CCD observations of W UMa-type eclipsing binary SS Arietis were made for ten nights from November 1996 to December 1996 at the Sobaeksan Astronomy Observatory. From the observed light curves, nine new times of minimum lights were derived from the Kwee and van Woerden’s method. Improved light elements for this system were determined from these minimum lights with all the published minima. The analysis of the times of minima of SS Ari confirms that the orbital period of SS Ari has been suffering from a sinusoidal variation as the suggestions of other previous investigators (Kaluzny & Pojmanski 1984, Demircan & Selam 1993). The calculation shows that the cyclic period change has a period of about 56.3yrs with an amplitude of about 0.d052. The period variation has been discussed in terms of two potential mechanisms: 1) the light-time effect due to a hypothetical third body and 2) deformations in the convective envelope of a magnetically active component. The BVR light curves of SS Ari observed for about one month showed the existence of cycle to cycle light variations. Long-term light changes of SS Ari are discussed in terms of the period variation of the binary system.

scholarly journals CVs Around the Minimum Orbital Period

2015 ◽  
Vol 2 (1) ◽  
pp. 41-45
Author(s):  
S. Zharikov ◽  
G. Tovmassian
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Orbital Period ◽  
Cataclysmic Variables ◽  
Outer Edge ◽  
Light Curves ◽  
Mass Ratio ◽  
Period Limit ◽  
Bounce Back ◽  
The Continuum

We discussed features of Cataclysmic Variables at the period minimum. In general, most of them must be WZ Sge-type objects. Main characteristics of the prototype star (WZ Sge) are discussed. A part of WZ Sge-type objects has evolved past the period limit and formed the bounce back systems. We also explore conditions and structure of accretion disks in such systems. We show that the accretion disk in a system with extreme mass ratio grows in size reaching a 2:1 resonance radius and are relatively cool. They also become largely optically thin in the continuum, contributing to the total flux less than the stellar components of the system. In contrast, the viscosity and the temperature in spiral arms formed at the outer edge of the disk are higher and their contribution in continuum plays an increasingly important role. We model such disks and generate light curves which successfully simulate the observed double-humped light curves in the quiescence.

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