Recent investigations on the evolution of the inhomogeneities in the inflationary universe are reviewed. 1) Strict cosmological no hair theorem does not hold, but the class of inhomogeneous universe which evolve to homogeneous de Sitter universe is finite, i.e, “weak cosmic no hair theorem” holds. 2) High density regions in the inhomogeneous universe evolve to wormholes provided that i) the size of the regions is greater than the horizon length, but smaller than a critical length which is the function of the density contrast, and ii) the density is three times higher than that of surrounding region. 3) If wormholes are formed copiously in the period of inflation, they evolve to causally disconnected “child- universes”. In this scenario, the universe we are now observing is one of the locally flat regions.

The dispersion of the Crab nebula pulsar was measured as a function of time from 10 May 1969 to 24 July 1970. Transient events occurred in the middle of June each year which coincided with the occultation of the pulsar by the solar corona. In addition there were 2 or 3 distinct events which produced enhancements of several times 1016 electrons cm-2; these were characterized by rise times of about 50 days and decay times several times longer. One event correlated with the frejump of the pulsar at the end of September 1969 and with the observation of optical activity in the quency nebula. A discussion is given of the interpretation of the variations in dispersion measure.

During 1988–1990 Commission 7 has sponsored or co-sponsored several IAU conferences: Colloquium No. 109 “Application of Computer Technology to Dynamical Astronomy” (Gaithersburg, July 1988), Symposium No. 141 “Inertial Coordinate System on the Sky” (Pulkovo, October 1989), Colloquium No. 127 “Reference Frames” (Virginia Beach, October 1990), Colloquium No. 132 “Instability, Chaos and Predictability in Celestial Mechanics and Stellar Systems” (Delhi, October 1990). The colloquium No. 118 “Dynamics of Small Bodies in the Solar System” which was to be held in Nanjing in June 1989 had unfortunately to be postponed then cancelled. Other meetings of interest to the members of Commission 7 were the 2nd Alexander von Humbolt Colloquium on “Long Term Evolution of Planetary Systems” (Ramsau, March 1988), the Colloquium “Asteroids, Comets, Meteors III” (Uppsala, June 1989), the colloquium “Mécanique Céleste et Systèmes Hamiltoniens” (Luminy, May 1990) and the NATO Advanced Study Institute on “Predictability, Stability and Chaos in N-Body Dynamical Systems” (Cortina d’Ampezzo, August 1990).

Preliminary Hα observations with the TAURUS imaging spectrometer confirm a pattern of systematic radial motions in a section of spiral arm in M83. The velocity gradients are not consistent with those predicted for the neutral gas.

Non-circular motions have also been discovered in the central regions of the galaxy.

We have used archival Chandra-acis observations to search for X-ray emission from WR stars in the Magellanic Clouds (MCs), where the low interstellar absorption and known distances make it easy to compare X-ray luminosities with spectral types and binary status of WR stars. We have detected X-ray emission from ~20 WR stars in the MCs with X-ray luminosities of 6.6×1032-1.4×1035 ergs s–1. The analysis of the X-ray spectra of the brightest sources indicates that the X-ray emitting gas has temperatures ≥ 1.0×107 K, as expected in colliding winds. We will compare these results with the binary status of the WR stars to determine the amounts of the X-ray emission produced in the colliding winds for WR stars in binary systems and to assess the X-ray emission from single WR stars.

The observations were carried out in August, 1983 using the 75 cm telescope at Sierra Nevada Observatory in Spain. This telescope is equipped with a six-channel uvbyβ photometer for simultaneous measurements in uvby and the narrow and wide Hβ channels, respectively. The observations were collected during four nights in the four uvby filters and one more night was devoted to measuring β Cas in the n and w bands of the Hβ Crawford system. In all cases, a calibrated neutral filter was used for β Cas. The comparison star was Cl=HR 9085 (V=5.m55, F0III).

The analysis of frequencies was carried out using the Discrete Fourier Transform method, as described in López de Coca et al. (1984), to the observational uvby points collected. The periodograms showed a principal peak at v=9.91 cd−l. After prewhitening for this frequency, the resulting periodograms did not show any trace of another peak, suggesting the monoperiodic nature of this star, in agreement with Antonello et al. (1986). Under the assumption of monoperiodicity of β Cas, the classical O-C method can easily be applied. Nine times of maxima were obtained for the four nights by using the method described in Rodriguez et al. (1990), where each light maximum has been derived as an average over the four uvby bands. When the O-C method was applied, the least squares fit converged to a linear ephemeris with the following elements: To=2445568.d5097 (±0.d0007) and Po=0.d10091 (±0.d00002). This linear ephemeris satisfactorily reproduces our data of β Cas.

We propose a new method to constrain the actual state of the interstellar cloud that surrounds the solar system. Using Voyager UVS Lyman-α sky maps and the powerful principle of invariance, we derive the H distribution all along the spacecraft path. Provided current models of the heliopause interface between the solar and the interstellar winds, we extrapolate this distribution to farther distances from the Sun and infer in a self consistent way key parameters of the local cloud. Our findings are a high interstellar hydrogen density of ~ 0.24 cm−3 and a weak ionization .

The theoretical study of the evolution of massive stars has considerable relevance to many branches of observational astronomy. As an example, one may mention, first, the direct application of theoretical models in interpreting the observed properties of supergiants, and second, the use of calculations of the nucleosynthesis taking place in these stars, together with observed supergiant mass loss rates and supernova calculations, to estimate the rate and type of nucleosynthetic enrichment of the interstellar medium by supergiants.

V647 Tau was observed during a 1997 STEPHI campaign; 228 hr of observations in v were obtained, together with another 50 hr of simultaneous data in y. The data were analyzed and main results are discussed in the text.

The hypothesis that a significant fraction of Be stars are interacting binaries is discussed in general terms. The author believes that the observed Be stars are a mixture of three different types of objects. The weakest point of the single-star hypothesis is probably the difficulty in explaining the quasi-periodic V/R variations; the weakest point of the binary hypothesis appears to be the statistical expectancy of a fairly high number of eclipsing systems among them.

Over the past decade, we have come to realize that mass loss on the asymptotic giant branch (AGB) plays a significant role in the formation of planetary nebulae (PN). Mass ejected during the AGB can now be observed in haloes of PN and we believe that the main shell of PN is formed by the interaction of this material with a later-developed central-star wind. In this review, we show that the evolution from AGB to PN can be traced in a continuous infrared sequence. This sequence predicts properties of proto-PN which allow them to be identified.

Detailed analyses giving the chemical composition have been carried out for twelve K dwarfs. Iron over hydrogen values have been found. Estimates of the masses of these stars are given.

It is important for understanding stellar evolution to constrain observationally how overshoot occurs for stellar conditions. Simplified models of the dynamics (eg. Zahn 1991) indicate that overshoot results in a slightly subadiabatic region beyond the convectively unstable layers, followed by an almost discontinuous transition to radiative stratification. Abrupt changes such as this contribute with a characteristic periodic signal to the frequencies ωn,l, of modes of low degree l (Gough 1990). This signature may therefore be detectable for distant stars. Here we show that the signal is sensitive to the “severity” of the overshoot and, of practical importance for the solar case, how it may be extracted from modes of higher degree. Finally we apply our method to solar data.

To analyze the applicability of the method, we consider four stellar models, Z1 — Z4, with solar mass, radius (R) and luminosity; of these, Z2 and Z4 have overshoot. The bases of the nearly adiabatically stratified region in the models are at radii rd/R = .729, .713, .713 and .700 respectively.

ESO has two telescope projects: the NTT (New Technology Telescope) with 3.5 m aperture and the VLT (Very Large Telescope) with 16 m equivalent aperture. The former is already in the engineering phase and should be completed in 1987; the latter is still in the study phase and will be described at this conference by our colleague, D. Enard.

This paper is concerned with the primary support system of the NTT. The basic principles and layout of this support have already been described in the literature 1,2,3).

In this paper, we present the NORT, a network of oriental robotic telescopes originally proposed in 1993 by Querci & Querci to study stellar variability. The NORT project covers all of northern Africa and Asia near the tropic of Cancer. The interest generated among a number of astronomers in countries from the Arab World and Asia offers a solid basis for the rebirth of astronomy and astrophysics and space sciences in developing countries. The number of national projects for telescopes in different countries makes the NORT a framework of choice to coordinate and stimulate these separate efforts by the creation of a NORT steering committee.

Using the WENSS survey, we have selected a complete sample of 26 Giant Radio Galaxies. We have investigated the properties of their radio structures using multifrequency radio observations. A spectral ageing analisys reveals that, among other things, that these sources are typically 50 — 100 Myr old and that their lobes have higher advance velocities than smaller sources of similar radio power. Further, we find pressure gradients in their radio lobes, suggesting that the lobes are still overpressured with respect to the environment. We find no evidence for a cosmological evolution of the radio lobe pressures with increasing redshift, at least up to z ∼ 0.3, other than that caused by our selection technique. A faint, higher redshift sample of giant sources is needed to constrain the pressure in their environments, the IGM. We are well underway with selecting such a sample, and the GMRT can play an important role in studying the radio properties of these sources.

We are engaged in a program to monitor radial velocity variability in proto-planetary nebulae (PPN). Observations are being made with the radial velocity spectrometer at the DAO, with a precision of ±0.5 km s−1. Radial velocity variability can arise from binary motion and/or pulsation in these post-AGB stars. The demonstration of a binary nature for some of these objects can have important implications for the understanding of their physical properties, and for the shaping of their circumstellar shells.

During the past five years, a total of about 180 U-lines has been observed by the author and others in the 70-115 GHz region in the prominent molecular clouds Sgr B2 and Ori (KL). A program to identify the carriers of these lines has been undertaken. A computer code, incorporating nine different centrifugal distortion Hamiltonians, generates spectra of asymmetric rotors from given rotational and centrigugal-distortion constants. Spectra have been computed for ∼550 molecules that are considered potentially interesting astrophysically. Molecules were selected from Landolt-Bornstein Volumes IV (1967) and VI (1974) on Molecular Constants, and from the spectroscopic literature (1973 - present).

Probable dust counterparts of arching structures are looked for in two cases, (a) the Eridanus expanding shell, Heiles (1976) and (b) the extended Sco-Cen feature, Weaver (1977). Apparently the color excess data may be used to derive distance and dimension estimates of these structures.