After the report on flare stars presented by Ambartsumian and the author (1971) at the last Bamberg Colloquium, some success has been achieved in the study of these interesting objects.

Optical observations of stellar flares with high time-resolution undoubtedly proved the explosive character of this phenomenon and the non-thermal nature of the radiation that appears at least at the beginning of the flare. Parallel optical and radio observations of flares in stellar aggregates complicated the interpretation and showed how far we are from an understanding of the physical nature of this phenomenon. Finally, new optical observations of stellar flares in aggregates of different age confirmed the evolutionary significance of this stage in the life of a star and led to the study of certain regularities in the evolution of flare stars.

A new Edition of the Asiago Catalogue of QSOs (Barbieri et al. 1982) is available on magnetic tape. It contains essentially all the information of the previous editions updated with the papers published before Dec.31, 1984. The catalog should be essentially complete to that date in respect to objects having slit spectra (2330 objects), while it is seriously incomplete regarding candidates discovered by objective prism or grism/grens surveys after 1982 (279 such objects included in the present version).

The question posed by the title is not yet conclusively resolved. Nonetheless, determinations of the lunar tidal acceleration based on dynamical time scales are now in reasonable accord with one another, whether based on the transits of Mercury, ancient eclipse observations, ocean tide models, or artificial satellite observations; these give a purely tidal component of −28.8 ± 1.5 “/cy2. Lunar occultations and laser ranging now give concordant results for the total anomalous acceleration of about −22.8 ± 1.5. The difference in these results gives an acceleration of possible cosmological origin of ṅ/n = +3.5 ± 1.2 × 10−11 per year, which is also consistent with very preliminary planetary radar studies. If interpreted in the scalar covariant cosmology of Canuto and Hsieh, this implies that Ġ/G = (−6.9 ± 2.4) × 10−11 per year, if measured in atomic time, but zero if measured in dynamical time. The implications for relativity and cosmology are discussed briefly in the paper, scheduled for the Astrophysical Journal issue of 1 September 1981.

The evolution of the orbits of 19 asteroids of particular interest has been studied over the interval 1660–2060, perturbations by Venus to Pluto being taken into account. Information was obtained about the encounters with Venus, the Earth, and Mars. A few approaches of Hidalgo to Jupiter were noted. In distinction to the orbits of short-period comets, the orbits of the 19 asteroids are stable throughout the 400-yr interval.

In δ Scuti star models the photometric amplitudes and phases exhibit a strong dependence on convection, which enters through the complex parameter,f, that describes the bolometric flux variation. We present a new method of extracting l and f from multi-colour data and apply it to several δ Scuti stars. The inferred values of f are sufficiently accurate to yield a useful constraint on models of stellar convection.

Evidence for superclustering of galaxies includes the local supercluster, the large deviation of the observed surface distribution of clusters of galaxies from a random one, the cell size dependence of the index of clumpiness, the results of covariance function tests for correlations between different cluster centers and between clusters and individual galaxies, and a power-spectrum analysis. All tests give results that indicate or are compatible with the existence of inhomogeneities in the distribution of matter in space with linear diameters of 50 to 100 Mpc. If these are dynamically stable superclusters, they probably have internal velocity dispersions in the range 1000 to 3000 km s-1. The possible effects of superclustering on dynamical studies of individual clusters are discussed briefly.

Estimates of the masses and energies of the supernova explosions that resulted in the Cygnus Loop and similar remnants are revised downward on the basis of recent soft X-ray observations.

The rotational energy transfer of NH3, OH and D2CO in inelastic collisions with He and H2 is studied in a crossed molecular beam experiment. The molecules are prepared in a single initial state by rotational cooling in an adiabatic expansion followed by electrostatic state selection. Relative state-to-state cross sections are determined by measuring the collision induced redistribution of the population of the initial state by using state selective laser detection techniques. The results for NH3 and OH are compared to theoretical values obtained from quantum calculations. Except for NH3 — He where theory predicts a parity selection rule for transitions to the 33 and 43 states, which is not observed in the experiment, good agreement between experiment and theory is obtained.

In the context of the search of asteroid families (i.e. identification of minor planets as potential fragments of an old bigger body), the calculation of proper elements plays an important role. They are quasi-invariants of the motion, obtained by a double averaging process of the restricted N-body problem; firstly the osculating elements are averaged over the short periodic terms (namely the longitudes of the asteroid and of the perturbing planets) so to get the mean elements, and secondly, the mean elements are averaged over the long periodic terms (longitudes of the pericenters and of the nodes of the asteroid and of the perturbing planets) to obtain the proper elements.

To reach lower noise levels with the Hubble Space Telescope Fine Guidance Sensors (FGS) the photometric properties as well as the systematic effects affecting the data have been investigated.

A number of promising observational programs involving linear polarization measurements are discussed after consideration of the observational limits based on telescope size and instrumental accuracy. These projects include studies of interstellar extinction, circumstellar shells and extended envelopes, inhomogeneities on stellar surfaces such as nonradial pulsation, magnetic stars, and interactive binary systems.

Spherically symmetric models for classical novae as thermonuclear run-aways (TNR) of hydrogen-rich, accreted, envelopes on top of cold white dwarfs (WD) are in very good agreement with observations (Starrfield, Sparks & Truran 1974, 1985; Prialnik, Shara & Shaviv 1978; Prialnik 1986; MacDonald 1980). Multi-dimensional investigations are needed since the burning rate is very sensitive to the temperature and small fluctuations in temperature can lead to large differences between the flash times of different points on the burning shell; these differences can be much larger than the rise time of the nova light curve. Convection is assumed to be the mechanism that couples the burning process at different points in the shell so that the overall phenomena is spherically symmetric.

Six streams of dust were unexpectedly detected by the Ulysses dust detector while this spacecraft was approximately within one AU distance from Jupiter (Grün et al., 1993). Stream durations ranged from hours to days for individual streams. It was clear that the dust in these streams (or bursts), from their directionality of approach to the spacecraft and from the nearness of stream occurrences to Jupiter, emanated from the Jovian system.

Following the original report, Baguhl et al. (1994) later relaxed the criteria for differentiating true dust impacts from “noise pulses” and found almost triple the number of dust impacts in the six streams already found. They also found 5 more streams that, except for one stream, clearly emanated from the Jovian system. The criteria were relaxed in such a way as to not introduce “noise events” into the data.

Observations of the night-sky brightness were organized at 106 places in Japan by a promotion of the Environmental Agency with the help of many local governments. Two kinds of measurements were carried out: 1) Number of stars were counted in a region of triangle formed by Alpha Lyr, Epsilon Lyr, and Zeta Lyr by at least 10 contributors at each point. 2) Photographs of a star field at the zenith at each point were taken with the same type of camera and film. These results gave us a good idea on distribution of night-sky brightness in Japan.

It is becoming increasingly evident that the older stellar components of the Magellanic Clouds are significantly younger, on the average, than the old star component of the Galaxy. Magellanic Cloud red globular-like clusters of the NGC 419 variety, and the common field stars of similar type, are almost certainly to be classified as intermediate-age populations by galactic standards. The oldest galactic population, seen in the galactic halo, globular clusters, and oldest galactic clusters, is apparently very sparse in the Magellanic Clouds, although in the SMC at least something very similar is seen in and near NGC 121.

A method for testing the possible correlation between axial rotations of pairs of stars is developed. The test is applied to a sample of visual binaries. It is concluded that some kind of coupling between the spins of components of visual binaries does in fact exist.

Radial and nonradial pulsations are excited in low-mass helium stars with effective temperatures between 7000 and 35000 K. In the case of the most luminous stars, these are driven by strange-mode instabilities (Saio & Jeffery 1988). Less luminous helium stars are mostly non-variable, except around 25000 K. V652Her is the prototype radially pulsating helium star, with Teff ~ 25000 K and a pulsation period of 0ḍ08 (Hill et al. 1981). The pulsation was only understood to be driven by the K-mechanism with the introduction of Z-bump opacity (Saio 1993).

The importance of Z-bump instability in low-mass helium stars has been investigated further through a series of pulsation models (Jeffery & Saio 1999a). It is shown that Z-bump pulsations can persist to surprisingly high hydrogen abundances in low-mass stars, and may consequently be excited in several helium-rich hot subdwarfs with Teff ~ 25000 K. Within the Z-bump instability region, both radial and nonradial pulsations are excited, and multi-periodic variability is expected.

Pulsation properties are closely linked to the global dimensions of a pulsating star by the period – mean density relation. When spectroscopic measurements are also available, the twin constraints of period and surface gravity can place very tight limits on the stellar radius (Jeffery & Saio 1999b). These are in excellent agreement with independent measurements for V652 Her and place a lower limit on the mass of the recently discovered Z-bump pulsator BXCir (Kilkenny et al. 1999).