To understand the structure and evolution of the cataclysmic variables, we will need accurate values for their masses, dimensions, mass transfer rates, and other physical properties. Unfortunately, despite an abundance of observational data on these systems, there is a severe dearth of reliable, quantitative information about their fundamental physical properties. Only two cataclysmic variables, U Gem and EM Cyg, are simultaneously eclipsing binaries and double-lined spectroscopic binaries, and only for these two systems can masses and dimensions be determined with a minimum of assumptions (Stover 1981a; Stover, Robinson, and Nather 1981). Even if there were more systems like U Gem and EM Cyg, it is not obvious that our information would be any more reliable, because observers are often unable to agree on the values of the directly measured quantities used to determine physical properties. Thus, the radial velocity curve of the brightest dwarf nova, SS Cyg, has been measured independently 5 times in the last 30 years. The agreement among the measurements is unsatisfactory, and the reasons for the disagreement are not completely understood (Joy 1956; Kiplinger 1979; Stover et al. 1980; Cowley, Crampton, and Hutchings 1980; Walker 1981). The physical properties may still be unreliable when the disagreements are understood and eliminated, because there is considerable uncertainty about the proper way to extract physical properties from observational data. For example, the observed radial velocity curves of cataclysmic variables are believed to be different from the true radial velocity curves of their component stars, but the amount of difference and ways to correct for the difference are unknown.

The eclipsing variable AC Cancri, recently identified as a cataclysmic variable by Shugarov (1981) and Okazaki, Kitamura and Yamasaki (1982), was further studied in detail on the bases of UBVcolours, multi-channel photoelectric light curves and image-tube spectrograms which were newly obtained at Tokyo Astronomical Observatory. The result of analysis of these materials for the nature of the cataclysmic variable is presented.

We present results of recent spectroscopic observations of A) some LMC X-ray sources, B) the X-ray burster 1735-44, and C) the peculiar emission-line binary BE UMa. From the short time scale variations and inferred low mass components each shows some similarities to more classical CV's.

Spectroscopic observations of two very different objects are discussed: the first, SS433, is a wery massive binary system probably containing an unseen 0 or WR star and a black hole surrounded by a luminous precessing accretion disk (from which emanate spectacular relativistic jets); the second, GK Per, is a classical old nova consisting of a slightly evolved K2 star and an unseen white dwarf companion surrounded by an accretion disk which is less luminous than the K2 star.

WZ Sagittae was one of the first cataclysmic variables shown to be a binary system (Kraft 1961) from spectroscopic observations. Krzeminski (1962) found that WZ Sge was an eclipsing binary with an 81 min 38 s orbital period. Krzeminski and Kraft (1964, hereafter KK) in the first of many comprehensive analyses of the WZ Sge system to appear in the literature stated “a lower limit to certain detection of orbital velocity changes for the double emission feature is 2K = 75 km s-1 .” Interpreted as an upper limit to K^ of 37.5 km s-1 this fundamental result has remained untested for two decades, although interpretations and observations of WZ Sge have led to a vast literature. Despite the lack of a well determined orbital velocity, WZ Sge is one of the most thoroughly studied cataclysmic variables. The photometric properties during quiescence have been thoroughly studied and discussed (Robinson, et al. 1978; Fabian, et al. 1978; Ritter and Schroder 1979), although a consensus on model parameters has remained elusive.

We have observed Z And and other symbiotic stars at the Wise Observatory and have obtained absolute flux measurements of many emission lines. Preliminary analysis of the data shows that the line emitting gas is probably photoionized by a hot, T* ≳ 200,000 OK continuum, which can explain the extremely strong Hell lines. The hydrogen Balmer line intensities are different from what is predicted by recombination theory and the optical depths in Hα and Hβ must be significant. Our photoionization model can be used to deduce the geometry, density and temperature of the line emitting gas, and the nature of the hot companion.

KQ Mon, a new UX UMa type nova-like variable discovered by H.E. Bond, exhibits optical spectra, UBV and high speed photometric characteristics strongly similar to other members of the UX Ursa Majoris subset. However its ultraviolet spectra when compared with other UX UMa stars shed considerable light on the nature of these objects. Its spectrum is dominated by strong broad highly ionized absorption lines including the NV, SiIV and CIV UV resonance doublets. No emission lines or P Cygni type features are evident and the velocity displacements are smaller suggesting the absence of a hot high velocity wind characterizing other UX UMa stars. A physical interpretation of the UV absorption spectra and optical spectra and their observed temporal variations is presented. Based upon (1) high mass accretion rates derived by fitting the observations with theoretical continuum fluxes from steady accretion disk models by R.E. Williams, (2) the presence of outflowing winds with the determination of corresponding mass loss rates and properties of the theoretical wind models by Cassinelli, Olson and Stalio, and (3) new time independent steady state disk structure computations, a model is suggested to explain the observed properties of the UX UMa stars and their lack of major outbursts.

We report the first results of an observational campaign consisting of coordinated photoelectric photometry of Ex Hya from four observatories at different geographical longitudes for a total of 146 hours in April 1979.

Ex Hya was monitored differentially for a total of 109 hours, partly simultaneously at different telescopes. The largest time-interval of uninterrupted observation is of nearly 18 hours. 68 times of eclipse, and 89 times of maxima in the 67-minute cycle have been obtained. Figure 1 is an 0-C diagram representing all residuals listed by Vogt et al. (1980), and those as obtained during this run.

Following earlier work of Lynden-Bell & Pringle (1974) and Lightman (1974a, 1974b), Bath & Pringle (1981) have presented a simple method for studying the time-dependent evolution of viscous accretion discs. These models are axisymmetrlc, with the vertical structure reduced to integrated averages of local physical conditions. Published work examines models of dwarf nova eruptions driven by mass transfer bursts (Bath & Pringle 1981 – Paper I), eruptions produced by global viscous changes within the disc (Bath & Pringle 1982a Paper II), and the time-dependent properties of giant discs in symbiotic binaries (Bath & Pringle 1982b – Paper III).

It is now well established, following the classic work of Smak, Warner and Nather, that discs in dwarf novae possess an anisotropic radiation pattern responsible for the hump, or shoulder, that occurs prior to eclipse in the quiescent state, and, in systems with suitable inclination such as TT Gem, responsible also for the primary eclipse itself. In systems with higher inclination such as Z Cha, the primary eclipse is composed of both this anisotropic disc component and the inner-disc/white-dwarf primary component.

Simple theories of hydrogen shell flashes on accreting white dwarfs are used to find the requisite conditions for classical novae. It is shown that enhancement of CNO abundances, relative to the Sun, is necessary for fast novae yet slow novae, such as DQ Her, can still occur with large CNO abundances. An analysis of observational data indicates that the white dwarfs in nova binaries have masses typically 1.1 Mʘ. For some old novae, the accretion rate, deduced from the accretion disk luminosity, is too high to permit a strong enough hydrogen flash to give the observed nova strength. Some possible resolutions to this paradox are suggested.

Recurrent novae are probably not thermonuclear runaways on accreting white dwarfs.

Spectroscopic observations of CNO emission lines are presented for old nova systems, and possible excitation processes for the lines are considered. The Bowen fluorescence mechanism cannot generally be responsible for the strength of N III λ4640 because of the weakness of 0 III λ3429. Other CNO lines are observed which indicate that all of the lines are excited by resonance fluorescence of UV continuum radiation. Several nonfluorescent excited lines of carbon are also present in old novae, probably formed by recombination processes. The available data for the optical CNO lines suggest that non-solar CNO enhancements exist in quiescent novae, indicating that some of the binary systems may be evolved.

The extremely high velocity absorption components observed in the ultraviolet with IUE, could have been produced by a supercritical wind. In this case most radiation would have been emitted shortwards of Lyman a, even at the time of the first IUE observations.

Nova Aquilae 1982 was discovered on January 27, but was difficult to observe at first because of closeness to the sun. A number of IUE spectra were obtained by Blades and Snijders from February 24, and the results were communicated to members of the ESA + SERC nova target of opportunity team. A preliminary report concerning these spectra has been made by Snijders, Seaton and Blades (1982).

We describe infrared photometry and spectroscopy of Nova Aquilae 1982. The broadband observations suggest that the dust shell of Nova Aquilae was anomalous, while the spectroscopic observations point to the presence of molecules in the nova environment.

Nova Aquilae was discovered (Honda 1982) on 1982 January 27th. The visual light curve, based on visual estimates (IAU circulars), IUE FES counts (derived assuming (B-V) = 0) and photometry at the South African Astronomical Observatory (SAA0), suggest a fast nova with visual decay rate mv = 0.3 mag d-1. Spectral development and outburst amplitude suggest that the nova was discovered at maximum.

The observed X-ray to IR continuum energy distribution of the old-nova GK Per, corrected for the contribution of the late-type secondary and for i.s. extinction,is found to be consistent with the model of an accreting magnetic white dwarf. Furthermore, we discuss plausible modifications of the standard disc structure caused by the presence of magnetic field lines threading the disc and evaluate the contribution to the observed radiation field from several physical mechanisms.

We describe a model for the evolution of the infrared spectrum of the dust shell of nova NQ Vul. The effects of nucleation and grain growth, together with.extended, but diminishing, mass loss from the nova, are included. The variations in the effective temperature of the dust shell that occur near infrared maximum may be understood in terms of varying optical depth in a dust shell having significant temperature gradient. However, a more consistent picture is shown to combine interrelated optical depth and grain size variations.

Results of fitting blackbqdy and pseudoblackbody functions to infrared photometry for three classical novae are briefly summarised.