Accretion Disk in the Massive Binary Ry Scuti

Djurašević, G.; Vince, I.; Atanackovic, O.

doi:10.1088/0004-6256/136/2/767

Cited by 20 publications

(25 citation statements)

References 18 publications

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“…Among them, AF Gem, TU Her, AT Peg, TY Peg, Z Per, Y Psc, and X Tri are systems with low mass ratios, and consequently, they are strongly suspected to undergo a non-conservative MT era, accompanied by ML through the L3 point at a significant rate. Recently, light curves of several early-type systems with an accretion disk have been analyzed using the new improved code of Djurašević et al (2005Djurašević et al ( , 2008 for estimating the physical disk parameters. Their analysis has indicated the presence of a bright spot, a region on the disk edge opposite (and close) to the L3 point, through which matter is expected to escape from the system.…”

Section: Discussionmentioning

confidence: 99%

Efficiency of ETV diagrams as diagnostic tools for long-term period variations

Nanouris

Kalimeris

Antonopoulou

et al. 2015

A&A

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Context. The credibility of an eclipse timing variation (ETV) diagram analysis is investigated for various manifestations of the mass transfer and gravitational radiation processes in binary systems. The monotonicity of the period variations and the morphology of the respective ETV diagrams are thoroughly explored in both the direct impact and the accretion disk mode of mass transfer, accompanied by different types of mass and angular momentum losses (through a hot-spot emission from the gainer and via the L2/L3 points). Aims. Our primary objective concerns the traceability of each physical mechanism by means of an ETV diagram analysis. Also, possible critical mass ratio values are sought for those transfer modes that involve orbital angular momentum losses strong enough to dictate the secular period changes even when highly competitive mechanisms with the opposite direction act simultaneously. Methods. TheJ −Ṗ relation that governs the orbital evolution of a binary system is set to provide the exact solution for the period and the function expected to represent the subsequent eclipse timing variations. The angular momentum transport is parameterized through appropriate empirical relations, which are inferred from semi-analytical ballistic models. Then, we numerically determine the minimum temporal range over which a particular mechanism is rendered measurable, as well as the critical mass ratio values that signify monotonicity inversion in the period modulations. Results. Mass transfer rates comparable to or greater than 10 −8 M yr −1 are measurable for typical noise levels of the ETV diagrams, regardless of whether the process is conservative. However, the presence of a transient disk around the more massive component defines a critical mass ratio (q cr ≈ 0.83) above which the period turns out to decrease when still in the conservative regime, rendering the measurability of the anticipated variations a much more complicated task. The effects of gravitational radiation proved to be rather undetectable, except for systems with physical characteristics that only refer to cataclysmic variables. Conclusions. The monotonicity of the period variations and the curvature of the respective ETV diagrams depend strongly on the accretion mode and the degree of conservatism of the transfer process. Unlike the hot-spot effects, the Lagrangian points L2 and L3 support very efficient routes of strong angular momentum loss. It is further shown that escape of mass via the L3 point -when the donor is the less massive component -safely provides critical mass ratios above which the period is expected to decrease, no matter how intense the process is.

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Section: Discussionmentioning

confidence: 99%

Efficiency of ETV diagrams as diagnostic tools for long-term period variations

Nanouris

Kalimeris

Antonopoulou

et al. 2015

A&A

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“…In this paper, we modelled the UBV light curves of the eclipsing binary star V448 Cygni (Kumsiashvili & Kochiashvili 2003) by using our improved code for the systems with accretion disc (Djurašević et al 2008). The light‐curve analysis shows that the model with an optically and geometrically thick accretion disc fits the observations very well.…”

Section: Discussionmentioning

confidence: 99%

“…The light‐curve analysis of V448 Cygni, performed by means of our modified code (Djurašević et al 2008), demonstrated that this light‐curve fitting code represents a useful tool for the analysis of light curves and for modelling of any conically shaped accretion disc and any brightness feature appearing on the disc lateral side. However, caution is required when interpreting the results, since the large number of free parameters makes the determination of the unique solution difficult.…”

Section: Discussionmentioning

confidence: 99%

“…The disc edge is approximated by a cylindrical surface. In the current, modified version of the code (Djurašević, Vince & Atanacković 2008), the disc thickness can change linearly with radial distance. The conical form of the disc surface (that can be concave, convex or plane‐parallel as a special transient case) is described by the disc radius ( R d ), and by the disc thickness at the edge ( d e ) and at its centre ( d c ).…”

Section: Accretion Disc Model Of the Systemmentioning

confidence: 99%

“…The radiation from the conical surface of the disc depends on the radial temperature profile. Among the variety of simple power‐law radial temperature distribution profiles of the disc (Djurašević et al 2008) here we chose, as optimal, the following one: …”

Section: Accretion Disc Model Of the Systemmentioning

confidence: 99%

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Accretion disc in the massive V448 Cygni system

Djurašević

Vince

Khruzina³

et al. 2009

Monthly Notices of the Royal Astronomical Society

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The UBV light curves of the early-type eclipsing binary V448 Cygni, obtained at the Abastumani Astrophysical Observatory from 1964 to 1967, are re-analysed here. The analysis was made assuming the presence of an accretion disc in the system, as inferred from the light-curve shape and spectroscopic characteristics of the system. The Roche model of a binary was used, containing a geometrically and optically thick accretion disc around the hotter and more massive star. By solving the inverse problem, the orbital elements and the physical parameters of the system components and of the accretion disc were estimated. This result is important for understanding the star formation and evolution processes in the systems with massive components.Key words: accretion, accretion discs -binaries: eclipsing -stars: individual: V448 Cygnistars: mass-loss. • 23 10 ) was discovered by Wachmann (1939). Ashbrook (1941) classified it as a β-Lyrae-type eclipsing variable. Its orbital period is about 6.5 days. The spectroscopic classification of V448 Cygni is not quite certain. Various spectral types are assigned to its components. In the Henry Draper (HD) catalogue, it is classified as a B3 spectral type. On the other hand, based on the prominence of O II and Si III lines, Petrie (1956) classified the cooler, less massive component (donor) as B1 and the hotter and more massive component (gainer) as O9.5 V. By combining the spectroscopic orbit and light-curve solutions based on the photographic light curve (Ashbrook 1941), Harries, Hilditch & Hill (1997) determined the masses of components as 25.2 and 14.0 solar masses and the radii as 6.7 and 16.3 solar radii for the gainer and the donor, respectively, considering the orbital inclination to be 83.• 2. Both components of this binary are massive stars, thus making this system particularly important for our understanding of the star formation processes. The duration of the mass transfer process in the massive close binaries is very short and the mass transfer rate is very large giving rise to unusual physical conditions and chemical composition in such systems. Therefore, a good knowledge of the models of binaries like V448 Cygni is essential, and the determination of their parameters is both important and challenging. Kumsiashvili & Kochiashvili (2003) published their photoelectric observations of V448 Cygni in three colours (close to UBV E-mail: gdjurasevic@aob.bg.ac.yu photometric system) obtained in the period from 1964 to 1967. The orbital phase was rather evenly covered with about 540 observations, providing the light curves of high quality. The maxima of the light curves in quadratures significantly differ and the rising branches of principal minima are steeper than the falling ones. The opposite happens with the secondary minima. Kumsiashvili & Kochiashvili (2003) modelled the system assuming circular orbits and ellipsoidal components, but this model did not satisfactorily fit the observations. Later on Kumsiashvili, Kochiashvili & Djurašević (2005) introduced a Roche mo...

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Study of nonstationary processes in the close binary system RY Scuti

2009

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We present results of reanalysis of old electrophotometric data of early type close binary system RY Scuti obtained at the Abastumani Astrophysical Observatory, Georgia, during 1972Georgia, during -1990 years and at the Maidanak Observatory, Uzbekistan, during 1979-1991 years. It is revealed non-stable processes in RY Sct from period to period, from month to month and from year to year. This variation consists from the hundredths up to the tenths of a magnitude. Furthermore, periodical changes in the system's light are displayed near the first maximum on timescales of a few years. That is of great interest with regard to some similar variations seen in luminous blue variable (LBV) stars. This also could be closely related to the question of why RY Sct ejected its nebula.Keywords: Close binaries, early-type stars, individual RY Scuti.1. Introduction. RY Scuti is a unique massive binary star system in a rare transitional evolutionary phase. It is surrounded by a young circumstellar nebula. The system is thought to be a rare progenitor of a WR+OB system, so it may be a "Rosetta Stone" for understanding the late evolutionary stages of close binary stars -particularly the formation of close WR binaries by tidally-induced mass transfer and mass loss. So, the close binary RY Sct undergoes mass-transfer and mass exchange processes and has complicated structure in its outer atmospheric layers. It possibly suffers evolutionary changes in a comparatively short time interval that is significant for constructing an evolutionary model of the system.The short history of investigation of this binary system is as follows: Merrill 1 found the He II 4686 line in the spectrum of RY Sct being specific only to nebulae and their nuclei. There are strong forbidden lines of [Fe III] and [Si III] in the spectrum, as well as emission lines of hydrogen, helium and other elements. RY Sct was observed as a radio source 2. The presence of the intense emission lines and radio emission (as in  Lyr) favored the assumption that there may be a small H II region around RY Sct 3 . The star is strongly reddened by the surrounding gas and dust shell 4. Based on spectroscopic observations, Cowley and Hutchings 5 found that the binary system consists of two early-type supergiants with a mass ratio of q=M 2 /M 1 =1.25. Guirichin and Mardirossian 6 suggested that the secondary must be surrounded by a geometrically thick accretion disk, which can explain its anomalously low luminosity, and that RY Sct is similar to the peculiar  Lyr system and is currently on its way to become a Wolf-Rayet (WR) system. Milano et al.

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Accretion Disk in the Massive Binary Ry Scuti

Cited by 20 publications

References 18 publications

Efficiency of ETV diagrams as diagnostic tools for long-term period variations

Efficiency of ETV diagrams as diagnostic tools for long-term period variations

Accretion disc in the massive V448 Cygni system

Study of nonstationary processes in the close binary system RY Scuti

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