Semi-detached System Research Articles

Forty eclipsing binaries in the Small Magellanic Cloud: fundamental parameters and Cloud distance

We have conducted a programme to determine the fundamental parameters of a substantial number of eclipsing binaries of spectral types O and B in the Small Magellanic Cloud (SMC). New spectroscopic data, obtained with the two- degree- field (2dF) multi- object spectrograph on the 3.9- m Anglo- Australian Telescope, have been used in conjunction with photometry from the Optical Gravitational Lens Experiment (OGLE- II) data base of SMC eclipsing binaries. Previously we reported results for 10 systems; in this second and concluding paper we present spectral types, masses, radii, temperatures, surface gravities and luminosities for the components of a further 40 binaries. The uncertainties are typically +/- 10 per cent on masses, +/- 4 per cent on radii and +/- 0.07 on log L. The full sample of 50 OB- type eclipsing systems is the largest single set of fundamental parameters determined for high- mass binaries in any galaxy. We find that 21 of the systems studied are in detached configurations, 28 are in semidetached post- mass- transfer states, and one is a contact binary.The overall properties of the detached systems are consistent with theoretical models for the evolution of single stars with SMC metal abundances (Z similar or equal to 0.004); in particular, observed and evolutionary masses are in excellent agreement. Although there are no directly applicable published models, the overall properties of the semidetached systems are consistent with them being in the slow phase of mass transfer in case A. About 40 per cent of these semidetached systems show photometric evidence of orbital- phase- dependent absorption by a gas stream falling from the inner Lagrangian point on the secondary star towards the primary star. This sample demonstrates that case- A mass transfer is a common occurrence amongst high- mass binaries with initial orbital periods P less than or similar to 5 d, and that this slow phase has a comparable duration to the detached phase preceding it.Each system provides a primary distance indicator. We find a mean distance modulus to the SMC of 18.91 +/- 0.03 +/- 0.1 (internal and external uncertainties; D = 60.6 +/- 1.0 +/- 2.8 kpc). This value represents one of the most precise available determinations of the distance to the SMC.

Photometry of Eclipsing Binary Stars in the Large and Small Magellanic Clouds

AbstractThe light curves for three eclipsing binaries in the Magellanic Clouds have been obtained using CCD uVJIC photometry. One target in the LMC, MACHO*05:36:48.7−69:17:00, is an eccentric system, e = 0.20, with a period of 3.853534 ± 0.000005 d. Initial solutions indicate a primary component in the range Teff,1 = 20,000−35,000K and the secondary Teff,2 1000−2000K cooler than the primary, with inclinations ranging i = 84.2° − 86.0°. Two targets in the SMC, MOA J005018.4-723855 and MOA J005623.5−722123, have periods of 1.8399±0.0004 and 2.3199 ± 0.0003 days respectively. Both have circular orbits with the former being a semi-detached system.

Eclipsing spectroscopic binaries in the Small Magellanic Cloud

New results on the properties of eclipsing spectroscopic binary stars, in the Small Magellanic Cloud (SMC), that are composed of two massive stars of spectral types O and B are reviewed. The data sets include multi-colour photometry and spectroscopy of individual binaries, I-band photometry of large numbers of binaries from the OGLE II survey, and multiplexed spectroscopy of many binaries discovered by the OGLE survey. The detached systems studied so far suggest good agreement with the latest evolution models at SMC metallicity for single stars. The semi-detached systems are consistent with recent case A mass-exchange evolution models although the sample is not yet large enough to provide a test of the expected duration of the slow phase of mass transfer. The mean distance to the main body of the SMC is determined from one study of 10 OB binaries to be 60.0 ± 1.1 kpc.

Type-Ia supernovae in semidetached binaries

We consider the evolutionary scenarios for close binaries that lead to the formation of semidetached systems in which a white dwarf can accumulate the Chandrasekhar mass through mass accretion from its companion, a main sequence star or a subgiant of mass M ∼ 2M⊙. Such dwarfs probably explode as type-Ia supernovae or collapse to form a neutron star. The population synthesis method is used to analyze the dependence of the model rate of these events in the Galaxy on the common envelope parameter, the mass transfer rate, and the response of a main-sequence star to helium accretion at an intermediate evolutionary stage. The rate of explosions in semidetached systems of this type in the Galaxy was found to be no higher than ⋍0.2×10−3 yr−1, which is less than 10% of the lower level for the empirically estimated SNe Ia rate.

근접촉쌍성 AX Draconis의 광도곡선과 로쉬모형

2001년 3월부터 5월까지 총 11일간 소백산천문대의 61cm 망원경과 VR 필터를 사용하여 근접촉쌍성 AX Dra의 광도곡선을 완성하였다. 우리의 관측으로부터 7개(주극심 3개, 부극심 4개)의 새로운 극심시각과 최근의 관측자료에 맞는 광도요소를 결정하였다. Wilson-Devinney 쌍성모델과 q-search방법을 이용하여, 우리의 VR광도곡선을 다양한 로쉬모형과 질량비에 대하여 분석하였다. 그 결과, 우리는 식쌍성 AX Dra가 분리형이거나 반성은 로쉬로브를 채우고 주성은 거의 채운 준분리형인 FO Vir형 근접촉쌍성계임을 알아내었다. 또한, FO Vir형 근접촉쌍성계의 통계적인 연구(Shaw 1994)와 달리, 우리의 VR광도곡선은 모두 같은 형태의 O'Connell효과를 보이고 있으며 그 크기는 약 <TEX>$0^{m}.008$</TEX>정도이다. We completed the light curves of near-contact binary system AX Dra for 11 nights from March 2001 to May using the 61-cm reflector and VR filters at Sobaeksan Optical Astronomy Observatory. From our observations, seven new times of minimum light (three timings to. primary eclipse, four. for. secondary) and the light elements consistent with recent observations were determined. Using the Wilson-Devinney binary code and the q-search method, we analyzed our VR light curves for various Roche configurations and mass ratios. As the results, we found the eclipsing binary AX Dra to be the FO Vir-type near-contact binary system interpreted as a detached or a semi-detached system, with the secondary filling its Roche lobe and the primary almost. Unlike the statistical study(Shaw 1994) of the FO Vir-type near-contact binary system, our VR light curves showed the O'Connell effect of all the same type and it's dimensions was about <TEX>$0^{m}.008$</TEX>.

Evolution of Wolf-Rayet stars in binary systems: An analysis of the mass and orbital-eccentricity distributions

We have undertaken a statistical study of the component mass ratios and the orbital eccentricities of WR + O close binary, detached main-sequence (DMS), contact early-type (CE), and semidetached (SD) systems. A comparison of the characteristics of WR + O systems and of DMS, CE, and SD systems has enabled us to draw certain conclusions about the evolutionary paths of WR + O binaries and to demonstrate that up to 90% of all known WR + O binaries formed as a result of mass transfer in massive close O + O binary systems. Since there is a clear correlation between the component masses in SD systems with subgiants, the absence of an anticorrelation between the masses of the WR stars and O stars in WR + O binaries cannot be considered evidence against the formation of WR + O binaries via mass transfer. The spectroscopic transitional orbital period P tr sp corresponding to the transition from nearly circular orbits (e sp<0.1) to elliptical orbits (e sp≥0.1) is ∼14d for WR + O systems and ∼2d–3d for OB + OB systems. The period range in which all WR + O orbits are circular \((1\mathop d\limits_. 6 \leqslant P \leqslant 14^d )\) is close to the range for SD systems with subgiants, \(0\mathop d\limits_. 7 \leqslant P \leqslant 15^d \). The large difference between the P tr sp values for WR + O and OB + OB systems suggests that a mechanism of orbit circularization additional to that for OB + OB systems at the DMS stage (tidal dissipation of the orbital energy due to radiative damping of the dynamical tides) acts in WR + O binaries. It is natural to suggest mass transfer in the parent O + O binaries as this supplementary orbit-circularization mechanism. Since the transitional period between circular and elliptical orbits for close binaries with convective envelopes and ages of 5×109 years is \(P_{tr} = 12\mathop d\limits_. 4\), the orbits of most known SD systems with subgiants had enough time to circularize during the DMS stage, prior to the mass transfer. Thus, for most SD systems, mass transfer plays a secondary role in circularization of their orbits.

Ten eclipsing binaries in the Small Magellanic Cloud: fundamental parameters and Cloud distance

We have conducted a programme to determine the fundamental parameters of a substantial number of eclipsing binaries of spectral types O and B in the Small Magellanic Cloud (SMC). New spectroscopic data, obtained with the two- degree- field (2dF) multi- object spectrograph on the 3.9- m Anglo- Australian Telescope, have been used in conjunction with photometry from the Optical Gravitational Lens Experiment (OGLE- II) data base of SMC eclipsing binaries. Previously we reported results for 10 systems; in this second and concluding paper we present spectral types, masses, radii, temperatures, surface gravities and luminosities for the components of a further 40 binaries. The uncertainties are typically +/- 10 per cent on masses, +/- 4 per cent on radii and +/- 0.07 on log L. The full sample of 50 OB- type eclipsing systems is the largest single set of fundamental parameters determined for high- mass binaries in any galaxy. We find that 21 of the systems studied are in detached configurations, 28 are in semidetached post- mass- transfer states, and one is a contact binary.The overall properties of the detached systems are consistent with theoretical models for the evolution of single stars with SMC metal abundances (Z similar or equal to 0.004); in particular, observed and evolutionary masses are in excellent agreement. Although there are no directly applicable published models, the overall properties of the semidetached systems are consistent with them being in the slow phase of mass transfer in case A. About 40 per cent of these semidetached systems show photometric evidence of orbital- phase- dependent absorption by a gas stream falling from the inner Lagrangian point on the secondary star towards the primary star. This sample demonstrates that case- A mass transfer is a common occurrence amongst high- mass binaries with initial orbital periods P less than or similar to 5 d, and that this slow phase has a comparable duration to the detached phase preceding it.Each system provides a primary distance indicator. We find a mean distance modulus to the SMC of 18.91 +/- 0.03 +/- 0.1 (internal and external uncertainties; D = 60.6 +/- 1.0 +/- 2.8 kpc). This value represents one of the most precise available determinations of the distance to the SMC.

The Classification and Orbital Period of WD 2154+408: A New Short‐Period Post–Common‐Envelope Binary

ABSTRACTWe present orbit‐sampled photometry of the binary system WD 2154+408. The photometric study reveals a period of P = 0.26772 day, which is taken to be the orbital period of the binary. No evidence is seen for either an accretion disk or mass transfer, leading to the conclusion that WD 2154+408 is not a contact or semidetached system but has detached components with a visible irradiation effect. The short orbital period also leads to the conclusion that the system passed through a common‐envelope phase at some time in the past. A single spectrum is shown exhibiting both narrow emission and broad absorption components of the Hβ line. This and the photometric variations are consistent with the system being a post–common‐envelope binary consisting of a hot white dwarf primary and a cool irradiated companion.

Photometric Solutions for Semidetached Eclipsing Binaries: Selection of Distance Indicators in the Small Magellanic Cloud

Estimation of distances to nearby galaxies by the use of eclipsing binaries as standard candles has recently become feasible because of new large-scale instruments and the discovery of thousands of eclipsing binaries as spin-off from Galactic microlensing surveys. Published measurements of distances to detached eclipsing binaries in the Large Magellanic Cloud combine stellar surface areas (in absolute units) determined from photometric light and radial velocity curves with surface brightnesses from model atmospheres and observed spectra. The method does not require the stars to be normal or undistorted and is not limited in its applicability to the well-detached systems that have traditionally been considered. We discuss the potential usefulness of semidetached vis a vis detached eclipsing binaries for distance determination and examine and quantify criteria for their selection from large catalogs. Following our earlier paper on detached binaries in the Small Magellanic Cloud (SMC), we carry out semidetached light-curve solutions for SMC binaries discovered by the OGLE collaboration, identify candidates for SMC distance estimation that can be targets of future high-quality observations, and tabulate results of OGLE light-curve solutions. We point out that semidetached binaries have important advantages over well-detached systems as standard candles, although this idea runs counter to the usual view that the latter are optimal distance indicators. Potential advantages are that (1) light-curve solutions can be strengthened by exploiting lobe-filling configurations, (2) only single-lined spectra may be needed for radial velocities because the mass ratio can be determined from photometry in the case of complete eclipses, and (3) nearly all semidetached binaries have sensibly circular orbits, which is not true for detached binaries. We carry out simulations with synthetic data to see if semidetached binaries can be reliably identified and to quantify the accuracy of solutions. The simulations were done for detached as well as semidetached binaries so as to constitute a proper controlled study. The simulations demonstrate two additional advantages for semidetached distance determination candidates; (4) the well-known difficulty in distinguishing solutions with interchanged radii (aliasing) is much less severe for semidetached than for detached binaries and (5) the condition of complete eclipse (which removes a near degeneracy between inclination and the ratio of the radii) is identified with improved reliability. In many cases we find that parameters are accurately determined (e.g., relative errors in radii smaller than 10%) and that detached and semidetached systems can be distinguished. We select 36 candidate semidetached systems (although seven of these are doubtful because of large mass ratios or periods) from the OGLE SMC eclipsing binary catalog. We expected that most semidetached candidates would have light curves similar to those of common Algol binaries, but that turned out not to be the case, and we note that fully Algol-like light curves are nearly absent in the OGLE sample. We discuss possible explanations for the near absence of obvious Algols in OGLE, including whether their paucity is real or apparent.

δ Sct-Type Pulsators in Eclipsing Binary Systems: the Case of RZ Cas

AbstractRZ Cas is an Algol-type eclipsing binary system where the primary component was recently discovered as a δ Set pulsator. A three-continent multisite photometric campaign was carried out during 1999. Preliminary results are reported here indicating a semi-detached system where the secondary fills its Roche lobe. The light curves also suggest a hot spot on the surface of the primary component as a consequence of the impact of the mass stream from the secondary. The pulsational behaviour can be well described with only one frequency.

Numerical Methods for the Simulation of Dynamical Mass Transfer in Binaries

We describe computational tools that have been developed to simulate dynamical mass transfer in semidetached, polytropic binaries that are initially executing synchronous rotation upon circular orbits. Initial equilibrium models are generated with a self-consistent field algorithm; models are then evolved in time with a parallel, explicit, Eulerian hydrodynamics code with no assumptions made about the symmetry of the system. Poisson's equation is solved along with the equations of ideal fluid mechanics to allow us to treat the nonlinear tidal distortion of the components in a fully self-consistent manner. We present results from several standard numerical experiments that have been conducted to assess the general viability and validity of our tools, and from benchmark simulations that follow the evolution of two detached systems through five full orbits (up to approximately 90 stellar dynamical times). These benchmark runs allow us to gauge the level of quantitative accuracy with which simulations of semidetached systems can be performed using presently available computing resources. We find that we should be able to resolve mass transfer at levels /M > few × 10-5 per orbit through approximately 20 orbits with each orbit taking about 30 hours of computing time on parallel computing platforms.

Infrared Spectroscopy of Symbiotic Stars. III. First Orbits for Three S-Type Systems

Infrared radial velocities have been used to derive the first well-determined orbital elements for the cool giants of three symbiotic systems, BF Cyg, V1329 Cyg, and V343 Ser=AS 289. Periods found for BF Cyg and V1329 Cyg from the radial velocity data are in good agreement with periods previously determined for their light variations, and the orbits are circular. Masses for the components of BF Cyg and V1329 Cyg were determined by combining our orbital elements for the cool giants with elements for their hot stars. BF Cyg and V1329 Cyg are shown to be detached binary systems. The third system, V343 Ser, has an orbital period of 450.5 days, a value that is typical for symbiotic binaries. However, the system is atypical because of its somewhat eccentric orbit, with e = 0.135 and the possibility that it is a semidetached system. An orbital inclination of 18° is estimated, indicating that V343 Ser does not eclipse.

Variations of Polarization in the Emission of ℴ Andromedae and LZ Cephei

The results of observations of polarization for the Be star ο And that are given are in fully satisfactory agreement with the results obtained by Arsenijevic, Vince, and Kubicela in 1974-1977. All these observations together support Harmanec's hypothesis that strengthening of the circumstellar envelope of ο And occurs during periastron passage of its companion, moving in an elongated orbit with a period of 8.5 years. The results of polarimetric observations of LZ Cep indicate that its slight, variable intrinsic polarization may originate, as in most semidetached systems, in the scattering of radiation of these stars from particles of matter escaping from the component that is filling its Roche lobe.

AV hydrae: A near-contact semi-detached binary with possible mass and angular momentum loss

The photoelectric observations of the neglected binary AV Hya published by Srivastava and Kandpal (1980) have been re-analyzed using Wilson-Devinney's synthetic light-curve program. The binary turns out to be a near-contact semi-detached system. The primary, more massive, more luminous and greater component, eclipsed at primary minimum, is detached from its Roche lobe (85%). The secondary fills its Roche lobe and has a temperature difference of DeltaT = -3414 K. As with other semi-detached binaries, the secondary is more evolved than that of the primary. The times of light minima of the eclipsing have been analyzed, showing that the orbital period of AV Hya undergoes a continuous decrease with a rate of dP/dE = -8.26 x 10(-8) day/year. The mass transfer between the two components can not explain the present orbital period variation since the secondary component is filling the Roche lobe. The orbital period change demonstrates that the system may undergo a secular mass and angular momentum loss and the system may evolve from the present short-period near-contact system into an A-type contact binary.

Radial Velocity Studies of Close Binary Stars. II.

Radial velocity measurements and simple sine-curve fits to the orbital velocity variations are presented for the second set of 10 contact binary systems. Eight systems are of the A type: AH Aur, CK Boo, DK Cyg, UZ Leo, XZ Leo, V839 Oph, GR Vir, and NN Vir; V842 Her is the only W type, while SV Equ appears to be a semidetached system seen at a low orbital inclination rather than a contact binary. Several of the studied systems are prime candidates for complete light and radial velocity synthesis solutions.

Can Combination of ‘Kozai Effect’ and Tidal Friction Produce Close Stellar and Planetary Orbits?

In binary stars, tidal friction dissipates a fraction of the orbital energy at constant angular momentum and will circularise binary orbits on a rather short rimescale compared with the nuclear rimescale, provided that at least one star of the binary has a radius comparable to the separation between binary components. This dissipation effectively ceases once the orbit is circularised. In a hierarchical triple system such dissipation cannot cease entirely, as neither inner nor outer orbit can become exactly circular because of the perturbation of the third distant body. Thus in such systems tidal friction can lead to a steady secular decrease of the inner semimajor axis, accompanied by transfer of angular momentum from the inner to the outer pair, persisting over the whole nuclear lifetime of the system. The situation can be even more dramatic if two orbits have high relative inclination i &gt; 40° It can be shown analytically and numerically (see e.g., Kozai 1962, Marchal 1990, Kiseleva 1996 and references therein) that for triple systems with high relative inclination there is a quasi-periodic change of the inner eccentricity (on a timescale ) during which it reaches a maximum value . This value only depends on the inclination i between the two orbital planes; other parameters affect only the timescale. For example, if we approximate a triple stellar system like β Per (Algol) (m1 = 0.8M⊙, m2 = 3.7M⊙, Pin = 2.87 days; m3 = 1.7M⊙, Pout = 1.86 yr, eout = 0.23; i = 100°) as three point masses, then the inner eccentricity ein cycles rather smoothly between 0 and 0.985, while i fluctuates between 100° and 140°. We call these fluctuations ‘Kozai cycles’. Such ‘Kozai cycles’ do not actually occur in this semi-detached system: they can be damped to a small value by tidal friction, but in fact they are also strongly reduced by the non-dissipative effect of the quadrupole moments of the two stars in the inner pair. This effect produces apsidal motion which is much more rapid than the apsidal motion due to the third star, and so prevents the Kozai cycles from operating.

Interacting OB star binaries: LZ Cep, SZ Cam and IU Aur

New spectroscopic observations of three O+O binary stars (LZ Cep, SZ Cam and IU Aur), obtained over a number of years at the Dominion Astrophysical Observatory, are analysed using state-of-the-art cross-correlation techniques to produce radial velocity curves. These results are combined with new (LZ Cep) and published (SZ Cam and IU Aur) photometry to yield masses, temperatures, radii and luminosities. We find that LZ Cep is a semi-detached system, in agreement with the results of Howarth et al., with the secondary star filling its Roche lobe. We find a distance modulus of 9.6 ± 0.2, which is slightly smaller than the distance modulus to Cep OB2 (= 9.9).The reddening of LZ Cep is also at the lower end of the cluster range, suggesting that the binary is located on the near side of the cluster. SZ Cam is a triple system, and we are able to measure the radial velocities of the three components that are observed in the absorption lines. A light-curve solution employing our new mass ratio shows that the short-period binary is detached. The third body emits about 40 per cent of the radiation from the system, and is probably a binary itself. The distance modulus for SZ Cam (= 9.88) is in good agreement with that of its parent cluster NGC 1502 (= 9.71). IU Aur is another triple system, although we are unable to find spectroscopic evidence for the tertiary. The close binary is semi-detached, with the secondary filling its Roche lobe. The distance modulus of the system is 11.0, which is in approximate agreement with that of the Aur OB1 association (= 10.6 ± 0.2). We note that the current models for interacting massive binaries all assume case B mass transfer, in which the mass-loser becomes a Wolf—Rayet star. Case A mass-transfer models (in which the mass-loser fills its Roche lobe while still on the main sequence) are required in order to see whether or not they can explain the observed properties of these interacting systems.

Subgiant luminosity excesses in eclipsing binary systems

It has been shown that radius and temperature excesses are largeat for subgiant stars in DS systems and low-mass and long-period SD systems, and smallest for subgiant stars in AR systems and lowmass and short-period SD systems. Subgiant stars in AR and more massive SD systems exhibit temperature deficiencies which are largest for the primaries of the AR systems. It is necessary to divide the class of SD systems into groups according to mass and orbital period while studying their properties. Investigations of subgiant stars from eclipsing binary systems have shown that they possess luminosity excesses for their masses. The excesses are determined as the difference between the observed subgiant luminosities and those of mainsequence stars with similar masses. Generally, an excess indicates that the subgiant does not follow the mass-luminosity relation. At the same time subgiants in some cases show luminosity excesses, and in other cases have radii excesses, which are inherent to detached subgiants of DS systems (Batten, 1976). Subgiant stars are present in three types of eclipsing binary stars. According to Svechnikov (1986) they can be companions in semi-detached systems (SD systems), in systems with a detached subgiant (DS systems) as well as primary and secondary stars in the eclipsing systems of AR Lacertae type (AR systems). In SD systems the subgiant completely fills up its Roche lobe, whereas in DS and AR systems the subgiant lies deep inside it. This testifies to the differences in subgiant star structure. Let us consider the problem of the origin of luminosity excesses calculating them for subgiant stars of different types of eclipsing binary systems and dividing them into the following components: a, radius excesses; b, temperature excesses. To calculate the excesses we used data on stars’ properties from Karetnikov and Andronov (1989); and from Karetnikov (1991) the averaged formulae of mass-radius and mass-temperature relations. We have also determined the correlations bf excesses with binary system size A, subgiant mass A4 aiid stellar mas ratio q.

Determination of the Physical Parameters of Binary Systems: A Statistical Approach

A statistical analysis of the solutions of binary systems from light and radial velocity curves is a very critical task, but necessary for labeling the parameters characterizing the solutions with suitable uncertainties in connection with the precision of the observations and the quality of the model used for the description of the systems. For this task, we introduced the χ2 test for variance, that is probably the best technique for statistical analysis of solutions, which has the not negligible advantage that it can be easily integrated in procedures like the Wilson-Price code. This procedure, developed by our group for the solution of eclipsing binary systems, is mainly based on the Wilson code (1992) for light curves and radial velocity curves synthesis and on the Price algorithm for the optimization of the solution. Within this context, we give first an heuristic proof of the convergence of the Price algorithm and then we discuss a general statistical approach to the solution of binary systems in order to establish the level of significance of the solutions together with a statistical estimate of the errors on the parameters. For the latter task, we used the Wilson code to generate the synthetic light and radial velocity curves of tens of systems (contact systems, semi-detached systems and detached systems), added with different levels of gaussian noise in agreement with the precision of modern photoelectric and spectroscopic observations. In this paper, we report the results of seven test cases, three contact systems, three semi-detached systems and one detached system, discussing the most relevant and general results obtained. We also show that the analysis of systems with and without radial velocity curves exhibits a good agreement, within the estimated errors, for the mass-ratios of all the statistically meaningful solutions.

Light Curve Variations of the Old Disk Eclipsing Binary R Canis Majoris

R CMa is one of the best observed low mass Algol-type systems, believed to be a semidetached system composed of a nearly spherical FOV primary and a less massive highly distorted K3 IV-V star. Most of the published light curves have asymmetries of one kind or another. Analysis of the individual light curves, dating back to over 75 years, yielded somewhat different orbital solutions depending on the epoch. These inconsistencies are caused by obvious differences in the shape of the light curves obtained at different epochs and by the different models used to find solutions.A series of light curves of R CMa (obtained at different epochs) have been analyzed by a new version of the Wilson-Devinney computing program to find a homogeneous solution. All parameters were adjusted to fit a light curve of each epoch. Then we found the weighted mean value of each parameter. These mean values were used as initial parameters and the potential and radius of each component were re-adjusted for each epoch to see the variation of radii for over 30 years. Several radial velocity curves were used to find spectroscopic parameters. The photometric parameters were combined with the corresponding spectroscopic parameters to calculate an absolute dimension of R CMa.Finally, we examined the IUE spectra of R CMa for existence of circumstellar gas in the system and evidence of magnetic activity on the cooler component. We also discuss the evolution of the system and possible observable real time evolutionary processes.