Orbital Period Modulation in SW Cygni

AbstractThe O–C curve of the Algol-type eclipsing binary SW Cyg was analyzed using the Kalimeris method. The observed period variations with time, the P(E) function and its rate of change dP/dE, were calculated. The plots of O–C values as well as of P(E) and dP/dE against ephemeris (E) all show rather regular period variations in this system. To reveal any cyclic period variations, the P(E) function was subjected to Fourier analysis. A cyclic period change of average ≈27.8-yr duration was obtained. Also a relative mass transfer rate of Δm/m = −1.1 × 10−9 yr−1 was estimated. Finally the existence of a third companion is suggested, and possible causes of period variations in the system are discussed.

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A Beat Phenomenon in Dwarf Nova Eruptions

International Astronomical Union Colloquium ◽

10.1017/s0252921100069396 ◽

1977 ◽

Vol 42 ◽

pp. 227-233

Author(s):

N. Vogt

Keyword(s):

Mass Transfer ◽

Orbital Period ◽

Transfer Rate ◽

Convection Zone ◽

Mass Transfer Rate ◽

Accretion Disc ◽

Light Curves ◽

Dwarf Nova ◽

Beat Phenomenon ◽

Photoelectric Observations

Photoelectric observations of the dwarf nova VW Hyi, obtained at the end of the December 1975 supermaximum, are presented. After decline from the outburst, the superhump period (0ḍ07622) combines with the orbital period (0ḍ07427) to a beat phenomenon: the O-C’s and the light curves of the orbital hump vary systematically with the phase of the beat period for at least one week after recovery from the supermaximum. It is suggested that the red secondary component, which rotates non-synchroneously with the superhump period, expands slightly at the beginning of a supermaximum and is heated up asymmetrically, probably due to instabilities in its convection zone. In addition, the increased mass transfer rate may trigger the long eruption in the accretion disc while short eruptions originate in the disc without participation of the secondary.

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Minimum Orbital Period of Cataclysmic Variables

International Astronomical Union Colloquium ◽

10.1017/s0252921100076545 ◽

1979 ◽

Vol 53 ◽

pp. 504-504

Author(s):

B. Paczynski ◽

W. Krzeminski

Keyword(s):

Mass Transfer ◽

Angular Momentum ◽

Orbital Period ◽

Time Scale ◽

Transfer Rate ◽

Main Sequence ◽

Mass Transfer Rate ◽

Cataclysmic Variables ◽

Transfer Rates ◽

Angular Momentum Loss

The shortest known orbital period of a cataclysmic binary with a hydrogen dwarf secondary filling its Roche lobe is about 80 minutes. Theoretically the shortest possible orbital period for such a system is less than 60 minutes. We tried to explain why the periods shorter than 80 minutes are not observed. We estimated the time scale of angular momentum loss of a cataclysmic binary and the resulting mass transfer rate. The minimum orbital period for a given Ṁ is obtained during the transition of the secondary from the Main Sequence onto the Degenerate Dwarf Sequence. Pmin ∝ Ṁ½ Therefore, only those systems can reach low P for which Ṁ is small. This explains why among the shortest period cataclysmic variables there are no novae: presumably their mass transfer rates are too large. It also indicates that “polars” (AM Her-type stars) and SU UMa-type stars should have low Ṁ.

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A Brown Dwarf Companion to the Nova-like Variable RW Tri

Galaxies ◽

10.3390/galaxies9040094 ◽

2021 ◽

Vol 9 (4) ◽

pp. 94

Author(s):

Zhibin Dai ◽

Shengbang Qian ◽

Indika Medagangoda

Keyword(s):

Mass Transfer ◽

Orbital Period ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Base Line ◽

Mass Ratio ◽

Brown Dwarf ◽

Period Range ◽

Period Decrease ◽

Cataclysmic Variable Evolution

The orbital period of Nova-like variable RW Tri is expected to experience a long-term evolution due to a stable mass transfer from the red dwarf to the white dwarf. By adding 297 new eclipse timings obtained from our own observations and a cross-identification of many databases, we fully reinvestigated the variations in orbital period of RW Tri, based on a total of 658 data points spanning over 80 years. The new O-C diagram demonstrates a more complicate pattern than a pure sinusoidal modulation shown in the previous O-C analyses. The best fit of the O-C variations is a quadratic-plus-sinusoidal curve with a period of 22.66 (2) years and a typical decrease rate of P˙ = −2d.32(4) × 10−9 yr−1. To explain secular orbital period decrease, the magnetic braking effect is required to cause the orbital angular moment loss in RW Tri with a mass ratio less than unity, while a conserved mass transfer is also enough for RW Tri with a mass ratio larger than unity. No matter what the mass ratio is, a slightly enhanced mass transfer rate, 2.4–5.3 × 10−9 M⊙ yr−1, derived from our O-C diagram, providing an evidence supporting the disk instability model and the standard/revised models of cataclysmic variable evolution, is almost the same as that obtained from the light-curve modeling. This further confirms our observed orbital period decrease and the controversial system parameter, mass transfer rate. Our updated O-C analysis further verifies the claimed cyclical changes of orbital period with a period range of 21–24 years, which is approximately one half of the results in the literature. In accordance with the light-travel time effect, this periodical variation shown in our new O-C diagram indicates a brown dwarf hidden in RW Tri at a coplanar orbit. Note that the large scatter in the data range of 0–3 × 104 cycles requires the high-precision photometry in the longer base line in the future.

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Dwarf Nova EX Hydrae

International Astronomical Union Colloquium ◽

10.1017/s0252921100076557 ◽

1979 ◽

Vol 53 ◽

pp. 505-505

Author(s):

N. Vogt ◽

W. Krzeminski ◽

C. Sterken

Keyword(s):

Mass Transfer ◽

Orbital Period ◽

Time Scale ◽

Mass Transfer Rate ◽

Period Change ◽

Momentum Exchange ◽

Radiation Losses ◽

Disc Rotation ◽

The Difference ◽

Photoelectric Observations

AbstractExtensive photoelectric observations of EX Hya were obtained between 1962 and 1976 at different telescopes and observatories. Evaluation of the data reveals a decrease of the orbital period at the rate Ṗ = −5.2 × 10−12. This period change is likely caused by mass transfer with angular momentum exchange between orbital motion and disc rotation on a time scale which is considerably shorter than the corresponding Kelvin – Helmholtz time scale. A rough estimate of the mass transfer rate gives Ṁ ⋍ 2 × 10−9 M⊙/yr. Gravitational radiation losses are negligible in the evolution of EX Hya. Furthermore we report the detection of a periodic modulation of the light-curve with a period of 0.046546447 days and mean amplitudes between 0.2 and 0.4 mag. (“67-minute cycle”). This oscillation remained coherent over the 14 years covered by our observations. The 67-minute variability resembles superhumps seen at supermaxima in SU UMa-type stars with the difference that it shows a 2:3 commensurability to the orbital period. We mention either (i) asynchronous rotation or pulsations of the red component, or (ii) asynchronous rotation of the magnetic primary, or (iii) resonances in the outer regions of the accretion disc as possible sources for this periodicity.

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Testing the disk instability model of cataclysmic variables

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833372 ◽

2018 ◽

Vol 617 ◽

pp. A26 ◽

Cited By ~ 17

Author(s):

Guillaume Dubus ◽

Magdalena Otulakowska-Hypka ◽

Jean-Pierre Lasota

Keyword(s):

Mass Transfer ◽

Orbital Period ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Sampling Rate ◽

Cataclysmic Variables ◽

Irregular Sampling ◽

Light Curves ◽

Stable Region ◽

Dwarf Novae

Context. The disk instability model (DIM) attributes the outbursts of dwarf novae to a thermal-viscous instability of their accretion disk, an instability to which nova-like stars are not subject. Aims. We aim to test the fundamental prediction of the DIM: the separation of cataclysmic variables (CVs) into nova-likes and dwarf novae depending on orbital period and mass transfer rate from the companion. Methods. We analyzed the light curves from a sample of ≈130 CVs with a parallax distance in the Gaia DR2 catalog to derive their average mass transfer rate. We validated the method for converting optical magnitude to mass accretion rate against theoretical light curves of dwarf novae. Results. Dwarf novae (resp. nova-likes) are consistently placed in the unstable (resp. stable) region of the orbital period – mass transfer rate plane predicted by the DIM. None of the analyzed systems present a challenge to the model. These results are robust against the possible sources of error and bias that we investigated. Light curves from Kepler or, in the future, the LSST or Plato surveys, could alleviate a major source of uncertainty, that is, the irregular sampling rate of the light curves, assuming good constraints can be set on the orbital parameters of the CVs that they happen to target. Conclusions. The disk instability model remains the solid basis on which to construct an understanding of accretion processes in CVs.

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Updated orbital ephemeris of the ADC source X 1822-371: a stable orbital expansion over 40 years

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935665 ◽

2019 ◽

Vol 625 ◽

pp. L12 ◽

Cited By ~ 1

Author(s):

S. M. Mazzola ◽

R. Iaria ◽

T. Di Salvo ◽

A. F. Gambino ◽

A. Marino ◽

...

Keyword(s):

Mass Transfer ◽

Orbital Period ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Optical Data ◽

Quadratic Model ◽

Arrival Times ◽

Companion Star ◽

X Ray ◽

Period Derivative

Aims. Source X 1822-371 is an eclipsing compact binary system with a period close to 5.57 h and an orbital period derivative Ṗorb of 1.51(7)×10−10 s s−1. The very high value of Ṗorb is compatible with a super-Eddington mass transfer rate from the companion star, as suggested by X-ray and optical data. The XMM-Newton observation taken in 2017 allows us to update the orbital ephemeris and verify whether the orbital period derivative has been stable over the past 40 yr. Methods. We added two new values obtained from the Rossi-XTE (RXTE) and XMM-Newton observations performed in 2011 and 2017, respectively, to the X-ray eclipse arrival times from 1977 to 2008. We estimated the number of orbital cycles and the delays of our eclipse arrival times spanning 40 yr, using as reference time the eclipse arrival time obtained from the RXTE observation taken in 1996. Results. Fitting the delays with a quadratic model, we found an orbital period Porb = 5.57062957(20) h and a Ṗorb value of 1.475(54)×10−10 s s−1. The addition of a cubic term to the model does not significantly improve the fit quality. We also determined a spin-period value of Pspin = 0.5915669(4) s and its first derivative Ṗspin = − 2.595(11) × 10−12 s s−1. Conclusions. Our results confirm the scenario of a super-Eddington mass transfer rate; we also exclude a gravitational coupling between the orbit and the change in the oblateness of the companion star triggered by the nuclear luminosity of the companion star.

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Free Convective Mass Transfer at Isosceles Triangular Surfaces of Varying Inclination

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20032080 ◽

2003 ◽

Vol 68 (11) ◽

pp. 2080-2092 ◽

Cited By ~ 1

Author(s):

Martin Keppert ◽

Josef Krýsa ◽

Anthony A. Wragg

Keyword(s):

Mass Transfer ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Mass Transfer Process ◽

Sulfate Solution ◽

Convective Mass Transfer ◽

Varying Length ◽

Inclined Surface ◽

Vertical Case ◽

Limiting Diffusion Current

The limiting diffusion current technique was used for investigation of free convective mass transfer at down-pointing up-facing isosceles triangular surfaces of varying length and inclination. As the mass transfer process, copper deposition from acidified copper(II) sulfate solution was used. It was found that the mass transfer rate increases with inclination from the vertical to the horizontal position and decreases with length of inclined surface. Correlation equations for 7 angles from 0 to 90° were found. The exponent in the ShL-RaL correlation ranged from 0.247 for the vertical case, indicating laminar flow, to 0.32 for inclinations of 60 to 90°, indicating mixed or turbulent flow. The general correlation ShL = 0.358(RaL sin θ)0.30 for the RaL sin θ range from 7 × 106 to 2 × 1011 and inclination range from 15 to 90° was obtained.

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