RY Sct Research Articles

The Massive Binary System RY Sct – New Solution of the Light Curves

RY Sct is a unique massive binary star system in a short transitional evolutionary phase. It is an eclipsing binary where both stars have overfilled their Roche cavities, so that the system is in an “overcontact” state. It is surrounded by a young circumstellar nebula. The binary is regarded as a rare progenitor of a type WR+OB system. RY Sct is close to the Eddington luminosity limit, so that radiative pressure plays an important role in mass loss. At least one of the components of the close binary may be associated with a rare class of LBV stars or the so-called S Doradus variables. We have calculated the orbital elements using the old photometric data of Zakirov and Kumsiashvili and new spectral data, together with an analysis of HST observations. A model was examined according to which the components of RY Sct are in an overcontact state and fill their Roche cavities. The brighter primary component transfers mass to the more massive but less bright secondary. The binary system is surrounded by a common envelope. As initial parameters we, chose a mass ratio q = 4.42 and orbital period P = 11d.12471, and used an orbital inclination of i = 75.6°.

Spectral observations of the eclipsing binary RY Sct

Spectral observations of the eclipsing binary RY Sct during 2005 and 2009 on the 2.6-m telescope at the Byurakan Observatory are reported. Although RY Sct requires further, more detailed study, the present limited observations reveal a number of important aspects of this star. The maxima of the equivalent widths are observed close to the primary minimum, while their minima are detected at the brightness maximum, where the spectral lines have very narrow profiles. Emission in the HeI λ6678A line was seen throughout the observation period, but transforms into weak absorption halfway between the secondary minimum and the maximum. The observed P-Cyg type changes in the profile of some lines indicates a variable outflow of mass from the star. Estimates of the average velocity based on the blue components of the absorption lines yield roughly 400 km/s. The main observational characteristics of RY Sct are closely related to its orbital period. In all likelihood, its complicated spectrum and features are at least partially caused by intense, variable outflows of matter.

ACCRETION DISK IN THE MASSIVE BINARY RY SCUTI

The UBVR light curves of the massive eclipsing binary RY Sct, obtained at the Maidanak Observatory from 1979 to 1992, have been re-analyzed in order to prove the hypothesis of the presence of an accretion disk in the system. This hypothesis is supported by a new spectroscopic study of Grundstrom et al., and by a specific light-curve shape exhibiting a slight asymmetry around the secondary minima and a small difference in the height of the successive maxima. The light-curve analysis was performed using a Roche model of a binary containing a geometrically and optically thick accretion disk around the more massive primary star. By solving the inverse problem, the orbital elements and the physical parameters of the system components and of the accretion disk were estimated for all the individual UBVR light curves. The model gives a consistent solution for the RY Sct binary system and supports the hypothesis of the existence of an optically thick disk around the massive component. Our results suggest a mass exchange between the components and a mass loss from the system. This could be considered as a possible mechanism of the formation of the accretion disk around the more massive component and of the circumbinary envelope of toroidal form in the orbital plane of the system.

A new unique phenomenon for the RY Scuti binary star

We present the results of reanalysis of old electrophotometric data on RY Scuti obtained at the Abastumani Astrophysical Observatory, Georgia, during 1972–1990 and at the Maidanak Observatory, Uzbekistan, during 1979–1991. Unstable processes in RY Sct from period to period, from month to month and from year to year are revealed. The magnitude of this variation is from hundredths to tenths. Furthermore, periodic changes in the system's light are displayed near the first maximum on timescales of a few years. This is of great interest with regard to some similar variations seen in luminous blue variable stars and, in particular, in S Dor-type stars. This also could be closely related to the question of why RY Sct ejected its nebula.

Properties of galactic B[e] supergiants

We present results of the first two-dimensional radiative transfer modelling of the eclipsing binary RY Sct and its dusty disc. Assuming an effective temperature T&#x0359 = 27 000K for both components and the distance D = 1.8 kpc, we derive the total luminosity L&#x0359 = 4.2 × 105 L. The optically thin dusty disc (tV ˜ 0.04 in the equatorial plane) extends from its inner boundary at R1 = 60AU to the distances of R2 ˜ 105 AU, where it blends into the interstellar medium. The very high energy output of the supergiants heats up the interstellar dust, well beyond the outer boundary, to temperatures of ~ 100 K.

A photometric study of the massive binary RY Sct

The present study deals with the problem of the estimation of the orbital and physical parameters for the EB-type eclipsing binary RY Sct, based on the interpretation of new photometric U B V R observations. The light curves obtained at the Maidanak Observatory during 1979-94 show a slight asymmetry around the secondary minima and a small difference in the height of the successive maxima. The light curves are analysed in the framework of the Roche computer model (Djurasevic [CITE]) by applying the inverse-problem method (Djurasevic [CITE]) based on Marquardt's ([CITE]) algorithm. The analysis shows that RY Sct system is in an overcontact configuration $(f_{\rm over}\sim 33\%)$ with $q=m_{2}/m_{1}=3.3$ and $i\sim 84\fdg 3$, generating total-annular eclipses. The basic parameters of the system and of the active region are estimated for all individual U, B, V and R light curves. Our results suggested a mass exchange between the components and mass loss through the outer Lagrangian point L 3 . This could be taken as a possible mechanism in the formation of the circumstellar envelope of toroidal form lying in the orbital plane of the system.

Stream formation in W Serpentis‐type binaries

AbstractBy the method proposed by Nazarenko (1993) and using observational data obtained by different authors, the physical conditions in the stream in the neighbourhood of the inner Lagrangian point L1 were calculated for three interacting binary systems of W Ser‐type: β Lyr, V367 Cyg, RY Sct. It is shown, that as a result of the evolutional expansion of the mass losing component the deep layers of its atmosphere reach the neighbourhood of the first Lagrangian point L1 and a stream of axial symmetric shape is formed. Its radius is comparable to the dimension of the mass losing component. The rate of the mass transfer increases up to 10−5 M⊙/yr. The calculated parameters of the stream in the neighbourhood of the point L1 explain the main observational properties of the investigated systems (existence of extended circumstellar matter with a developed structure, high mass transfer rate).

Results of a cooperative investigation of RY Scuti

Some preliminary results are given of a cooperative investigation of the highly interesting radio object RY Sct. From spectroscopic data the mass-ratio was found to be q=m2/m1≈3.3. An attempt to determine the helium content by model-atmosphere techniques has shown that the atmosphere of the primary component has a large helium excess; the star has every characteristic of a helium star formed by mass exchange in case B. The analysis suggests that RY Set may offer a rare chance to observe a massive system at the stage when “switching of the roles” is complete and a helium remnant with a hydrogen shell is beginning to develop the characteristics of a WR-star.

A review of early-type close binary systems

This is a review of close binary systems with very early spectral types (B, O, Of, and WR stars). We limit our selection to systems with Roche model photometric solution only. There are 10 contact systems known at present. Three of them (V701 Sco, BH Cen, and RZ Pyx) are located in the vicinity of the zero-age contact (ZC) according to a Spectral Type — Period diagram. Only the first two systems have absolute dimensions available. Both of these fall into the ZC zone in the logP-logm diagram and the logm-logR diagram. The system TU Mus was thought to be a ZC system is located in the evolved contact zone (EC) in the above diagrams. Both V701 Sco and BH Cen were thought to be having mass ratios about unity. With the much improved light curves of BH Cen and new analysis the mass ratio has been revised to 0.84! This result may favor Shu's model for early-type zero-age contact systems. The evolved systems might be undergone Case A mass exchange except for two systems (V729 Cyg and RY Sct) which might be from Case B. The systems V367 Cyg was classified by Plavec as a W Ser system may be a evolved contact system.

THE UNUSUAL RADIO BINARY RY SCUTI.

ABSTRACT Recently obtained spectrograms imply that RY Sct contains two massive stars embedded in an unusual nebulosity whose spectrum shows exceptionally strong (forbidden Fe III) emission. At least one component is probably H-deficient (or He-rich), which may result from the loss of the H-rich envelope. Rapid rotation is thought to be the cause of this. A modern light curve is required before a complete interpretation of the data can be made.

PHOTOMETRY OF SYMBIOTIC AND VV CEPHEI STARS IN THE NEAR INFRARED (WITH A NOTE ON MWC 56)

ABSTRACT The majority of symbiotic and VV Cephei stars have near infrared continua closely resembling those of late-type stars. Evidence for weak infrared excesses has been found in the three stars RY Sct, W Cep, and U Lac. RX Pup and V1O16 Cyg exhibit very prominent infrared excesses which are attributable to thermal radiation from circumstellar dust. The "Bep" star MWC 56, whose spectrum shows Fe ii and [Fe ii] emission lines in the blue, possesses the absorption lines of a C or K component in the red. No substantial infrared excess is present. Key words: near-infrared photometry - symbiotic stars - VV Cephei stars