The preliminary results of a search for OH/IR stars in the Galactic Centre using the VLA are presented. The goal of this project is to determine the mass density distribution from a few parsecs up to about 120 pc of the Galactic Centre using stellar kinematics. Up to now, 125 OH/IR stars have been found. The distribution of the stars is clearly elongated with the major axis parallel to the galactic equator. The stars show a rotation of 117 km s−1 deg−1 with a dispersion of 90 km s−1. Two preliminary models have been applied in order to determine the enclosed mass, resulting in M(r)=4.0·106·r1.4 Mo, where r is the galactocentric distance in parsecs.

The classical problem of determining the secular retardation of the Earth's rotation due to the effect of tides (oceanic and bodily) has an important geophysical value in determining the possible existence of processes inside the Earth, which lead to secular variations of rotation of the whole Earth or its external layers.

Using new cotidal charts of the world ocean calculated by Bogdanov for the main tidal waves M2, S2, K1 and O1 and using the method of moments of tidal forces the retarding moment was found to be 8.3 × 1023 dyn cm. This is twice the amount of previous evaluations. (This method is superior to the method of calculating the dissipation of energy or the moments of frictional forces). This amount corresponds to a retardation of 3.8 μs/century in the speed of the Earth's rotation. But the observations of the Sun give only 1.9 μs/century for the retardation. Thus, there seem to be nontidal and probably internal processes, which accelerate the Earth's rotation by about 2 μs/century. And this is without taking account of additional smaller effects of bodily tides. The search for these processes is an important problem.

The full text of the paper will be published in the magazine Physics of the Earth, No. 2, 1972.

The massive O and B-type stars will be among the first targets of the new generation of long baseline optical interferometers (such as the CHARA Array, a 400-m diameter distributed array of five 1-m telescopes). Many of these objects are binary stars for which joint astrometric and spectroscopic observations will provide masses and distances (e.g., 15 Mon; Gies et al. 1993), but there is also great interest in resolving disks of single stars. Early interferometric observations have already resolved the flattened circumstellar disks around some Be stars (Quirrenbach et al. 1994).

We determined individual distances to a small number of rather round, quite regularly shaped planetary nebulae by combining their angular expansion in the plane of the sky with a spectroscopically measured expansion along the line of sight. For this goal, we combined up to three epochs of Hubble Space Telescope imaging data and determined the respective proper motions of rim and shell edges, and of other features as well. Ground-based radial velocities are assigned separately to the nebular rims and shells and used to determine individual distances, thereby assuming that the expansions in the line-of-sight and in the plane of sky are equal. We employed 1D radiation-hydrodynamics simulations of planetary nebulae evolution to correct for the difference between the spectroscopically measured expansion velocities of rim and shell and the expansion speeds of their respective shock fronts.

Interpretation of current and future data calls for a continuous improvement in the theoretical modeling of CMB spectrum. We describe the new version of a numerical code, KYPRIX, specifically written to solve the Kompaneets equation in a cosmological context under general assumptions. We report on the equation formalism, and structure and computational aspects of the code. New physical options have been introduced in the current code version: the cosmological constant in the terms controlling the general expansion of the Universe, the relevant chemical abundances, and the ionization history, from recombination to cosmological reionization. We present some of fundamental tests we carried out to verify the accuracy, reliability, and performance of the code. All the tests demonstrate the reliability and versatility of the new code version and its accuracy and applicability to the scientific analysis of current CMB spectrum data and of much more precise measurements that will be available in the future.

Acoustic modes are well-suited probes to check the internal stellar structure and bring interesting constraints on turbulence regions, mixing in stellar interiors and magnetic fields. The SOHO satellite, through the helioseismic instruments GOLF, MDI and VIRGO, has significantly improved the knowledge of these modes owing to an excellent duty cycle (greater than 90%) and the capability to detect very low amplitude modes, down to 3 mm/s. Five years of the SOHO misson guarantee an accurate view of the solar interior, weakly dependent on the turbulent surface, from the energy-generating core to the surface.

The recent results allow us to verify some of the theoretical assumptions of stellar modelling. The tachocline layers, located in a narrow region at the base of the convection zone, support an hydro (or magnetohydro) dynamical instability which induces mixing and results in 7Li depletion in accordance with photospheric observations. On the contrary, central mixing is not favoured by the present observations. Nuclear reaction rates of the pp chain are now constrained by the behaviour of the sound speed and density. Döppler velocity measurements appear as an excellent technique to follow in real time the temporal evolution of the luminosity produced in the core. Some puzzling questions about dynamical effects in stellar plasmas can now start to be addressed for the first time. The theoretical neutrino emissions can be now directly deduced from our helioseismic vision of the energy-generating core.

Nowadays, helioseismology provides a dynamical vision of the external half of the Sun (20% in mass), as a result of the extraction of the sound speed, density, rotation profiles and of the time evolution of velocity measurements. Below, the classical static vision of the nuclear region persists because of the poor spatial resolution offered by acoustic modes (±6% in radius, 10% in mass) and the long integration time (several years). Gravity modes will be extremely useful to improve the spatial resolution in the radiative region. The extended observations with the SOHO satellite may be extremely useful to detect some of these modes.

UV spectra with 15 km s-1 resolution of bright stars have been searched for Fell and Mgll interstellar lines. We present equivalent widths of absorption for 8 stars and find average line-of-sight densities n(FeII)= 4 10-8 and n(MgII)= 2 10-7 cm-3 . This represents approximately n(H)= 0.03 cm-3.

The presently available multidimensional dusty gasdynamic cometary atmosphere models are reviewed. This paper examines the simplifying assumptions and their potential consequences. Special attention is paid to the question of potential nightside dust accumulation presently predicted by Korosmezey and Gombosi (1989).

Magnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.

Several tracers of the cold interstellar medium in its quiescent phase reveal common unexpected properties: the fractal nature of the emission contour levels, the self-similar brightness distribution, the existence of small unresolved fragments of dense gas in various environments, and a highly turbulent velocity field. In spite of the difficulties met in interpreting these data, they are important bearings in our understanding of the structure, the physics and the chemistry of this medium.

Observing supernova remnants provides important clues to the nature of supernova explosions. Conversely, the late stages of stellar evolution and the mechanism of supernova explosions affect supernova remnants through circumstellar matter, stellar remnants, and nucleosynthesis. The elements of supernova classification and the connection between supernova type and remnant properties are explored. A special emphasis is placed on SN 1987a which provides a unique opportunity to learn the connection between the star that exploded (whose name we know) and the remnant that will develop in our lifetimes.

The stellar populations give traces of the formation history of the bulges. The metallicity distribution of K-giants in the Galactic bulge resembles to that of the giant ellipticals. There seems to be no conspicuous colour-magnitude relation intrinsic to the bulges. This can be explained if the bulges formed by the dissipative collapse of central regions of proto-galaxies followed by the supernova-driven bulge wind which was induced later than the dwarf ellipticals of the similar mass (the biased wind). Unfortunately, the observational data available at present of stellar populations of the bulges are not yet sufficient to get a firm conclusion on the origin of the bulges.

We present the first results of a series of Monte-Carlo simulations investigating the imprints of a central black hole on the core structure of globular clusters. We investigate the three-dimensional and the projected density profile of the inner regions of idealized as well as more realistic globular cluster models, taking into account a stellar mass spectrum, stellar evolution and allowing for a larger, more realistic, number of stars than was previously possible with direct N-body methods. We compare our results to other N-body simulations published previously in the literature.

The characteristics of large-scale two-ribbon flares and dark points observed in He I λ10830 are summarized and compared with observations of these phenomena at other wavelengths and with the underlying magnetic field.

In this paper, I review our current understanding of interstellar scintillations (ISS) of pulsars. The emphasis is on new results that have appeared during the last five years. The topics covered include (i) review of the understanding of refractive ISS (ii) the shape of the spectrum of electron density fluctuations in the interstellar medium (iii) the distribution of scattering plasma in the Galaxy (iv) resolving pulsar emission regions using ISS and (v) ISS and pulsar velocities.

We present an ISOCAM-CVF map of the ρ Oph A region, covering 3′ × 3′. For each 6 arcsec2 pixel, we extract the spectrum from 5–15 μm. We determine the fluxes of the main PAH features by fitting Lorentzian profiles to the spectrum. The peaks of the various PAH components correspond well with the known positions of the PDRs in this vicinity. The spectrum in several pixels exhibits strong rotational lines of molecular hydrogen which can be used to derive the physical properties of the cloud. The H2 emission traces the hot gas of the bipolar CO outflow from VLA1623.

Rotation is a key parameter in the evolution of massive stars, affecting their evolution, chemical yields, ionizing photon budget, and final fate. We determined the projected rotational velocity, υe sin i, of ~330 O-type objects, i.e. ~210 spectroscopic single stars and ~110 primaries in binary systems, in the Tarantula nebula or 30 Doradus (30 Dor) region. The observations were taken using VLT/FLAMES and constitute the largest homogeneous dataset of multi-epoch spectroscopy of O-type stars currently available. The most distinctive feature of the υe sin i distributions of the presumed-single stars and primaries in 30 Dor is a low-velocity peak at around 100 km s−1. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak in the single star sample is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tail of stars rotating more rapidly than 300 km s−1, the sample of primaries does not feature such a high-velocity tail. The tail of the presumed-single star distribution is attributed for the most part – and could potentially be completely due – to spun-up binary products that appear as single stars or that have merged. This would be consistent with the lack of such post-interaction products in the binary sample, that is expected to be dominated by pre-interaction systems. The peak in this distribution is broader and is shifted toward somewhat higher spin rates compared to the distribution of presumed-single stars. Systems displaying large radial velocity variations, typical for short period systems, appear mostly responsible for these differences.

Despite the early optical detection of the Crab pulsar in 1969, optical pulsars have become the poor cousin of the neutron star family. Only five normal pulsars have been observed to pulse in the optical waveband. A further three magnetars/SGRs have been detected in the optical/near IR. Optical pulsars are intrinsically faint with a first order luminosity, predicted by Pacini, to be proportional to P−10, where P is the pulsar’s period. Consequently they require both large telescopes, generally over-subscribed, and long exposure times, generally difficult to get. However optical observations have the benefit that polarisation and spectral observations are possible compared to X-ray and gamma-ray observations where polarisation measurements are limited. Over the next decade the number of optical pulsars should increase as optical detectors approach 100% quantum efficiency and as we move into the era of extremely large telescopes where limiting fluxes will be 30 to 100 times fainter compared to existing optical telescopes.

Many complex organic molecules and inorganic solid-state compounds have been observed in the circumstellar shell of stars (both C-rich and O-rich) in the transition phase between Asymptotic Giant Branch (AGB) stars and Planetary Nebulae (PNe). This short (~102-104 years) phase of stellar evolution represents a wonderful laboratory for astrochemistry and provides severe constraints on any model of gas-phase and solid-state chemistry. One of the major challenges of present day astrophysics and astrochemistry is to understand the formation pathways of these complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene in the case of a C-rich chemistry and oxides and crystalline silicates in O-rich environments) in space. In this review, I present an observational review of the molecular processes in the late stages of stellar evolution with a special emphasis on the first detections of fullerenes and graphene in PNe.