[en] The basic physics is presented of a mechanism which explains dwarf nova outbursts as accretion disc instabilities. Briefly put, the strong and oppositely directed temperature dependences of opacity in hydrogen ionization regions drive a thermal instability which modulates mass transfer throughout the disc. It is also shown that the conventional thin disc treatment breaks down in cool regions, where the surface boundary condition dominates the structure. One major purpose of the paper is to modify the conventional treatment, to produce analytical approximations for many of the relationships of interest. When these results are applied to a schematic local treatment of disc flows, the prospect of a thermal limit cycle is revealed. Finally, these results will be particularly useful for time-dependent treatments of global accretion disc flow. (author)

[en] Einstein, IUE, optical multichannel spectrophotometry, and IR observations of Stepanian's star are discussed in terms of other known cataclysmics. While the X-ray flux and IUE emission-line data are similar to that of dwarf novae, the total continuum flux distribution from uv-IR is cooler (peaking near a 10,000 K blackbody) and is unlike either a stellar component or a classic steady-state disk. The IR data show no evidence for a late-type component

[en] For 25 years the conception has been well established that the overwhelming majority of chemical elements and their isotopes have been synthesized in stars during the course of stellar evolution, in particular during the advanced stages and in supernova explosions. Until now this general idea has not led to major difficulties or inconsistencies. On the contrary, the theoretical models have been very successful in explaining the observed abundances in meteorites, planets (including the earth), stars (including the sun) and galactic cosmic rays. Our present understanding of nucleosynthesis will be reviewed with special attention given to nucleosynthetic processes in primordial stars and supernovae. We will concentrate primarily on predictions which can be made for relative abundances rather than for absolute abundances, because the latter problem requires evolutionary models of the galaxy which are beyond the scope of this article. (orig.)

[en] An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km s^-₁, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (> or approx. =10 L/sub sun/) and low inclination angles with respect to the observer's line of sight. The mass loss rate for cataclysmic variables is of order 10^-₁₁ M/sub sun/ yr^-₁; this is from approx.10^-₂ to approx.10^-₃ of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed

[en] The author studies the past paths of the run-away star Zeta Oph from the OB association Sco-Cen, and of the run-away stars AE Aur, Mu Col and 53 Ari from the OB association Ori OB1, in connection with the question of the origin of these high velocities. Should the binary-hypothesis be adhered to (supernova explosion of one of the components) or, perhaps, dynamical evolution in young, dense clusters offer a clue to this phenomenon? It is shown that the latter hypothesis is very unlikely to apply to Zeta Oph. For the run-away stars from Orion conclusive evidence may well be obtained in the course of the next decade, from improved accuracy of the proper motions

[en] The Monoceros ring, a circular optical nebulosity approx. 3⁰.5 in diameter and centred at R.A. = 6sup(h)37sup(m), Dec. = 6⁰30'(lsup(II) = 205⁰.5, bsup(II) = 0⁰.2) is in good structural agreement with radio observations. A neutral hydrogen shell is also accurately projected on the ring. These observations are consistent with the Monoceros ring being a supernova remnant 90-100 pc in diameter expanding at about 45 km s^-1 and having an age of the order of a million years. Bright H II regions containing early-type stars (e.g., galactic cluster NGC 2244 in the Rosette nebula) and extremely young stars of the OB association Mon OB2 lie at the edges of the ring. The positional and temporal coincidence of the Mon OB2 association with a supernova remnant suggests that probably the star formation in this region is induced or speeded up by the passage of a supernova shock wave through the clumpy interstellar medium. (orig.)

[en] A program is described for development of an automated supernova search based upon complete remote computer control of a telescope and vidicon digital imaging system

[en] Evidence is reported for an intimate connection between a particular supernova and the solar system. It appears that a massive star exploded in the vicinity of the developing solar system at about the time the system condensed. This evidence comes from studies of the chemical elements in meteorites, and in particular, from measurements of the abundance of the various isotopes of certain elements. The kinetics of the solar system development from this explosion and the isotope-ratio evidence for these processes are described in some detail

[en] Results are given of a search for multiple Trapezium type systems in T associations in Orion based on examination of the Palomar Sky Survey Charts. It is found that among the multiple stars in the investigated T associations a large percentage are in star systems of the Trapezium type

[en] The origin of the chemical elements in nature is understood in terms of nuclear reactions which occur in a variety of cosmological settings. In order to develop a self-consistent explanation of these processes, extensive information from many diverse fields of science is required. First, one must know the characteristic abundances of the elements and their isotopes in the universe, for it is these values that any successful theory of nucleosynthesis must reproduce. Second, it is necessary to investigate all possible nuclear processes that might give rise to these abundances. Finally, an appropriate cosmological environment must be found which is capable of generating the essential nuclear reactions. The major sources of element production will be reviewed. These include: 1) Cosmological processes associated with the big bang; 2) Nucleosynthesis in stars during stellar evolution from main sequence stars through the supernova stage, and 3) Formation of elements via interactions of galactic cosmic rays with the interstellar medium. The relationship of recent measurements relevant to light element nucleosynthesis in the big band and the question of the expanding universe is discussed, as is the possibility of forming super-heavy elements during supernova explosions. (orig.)