Magnetic fields may be observed via the Zeeman effect, linear polarization of dust emission, and linear polarization of spectral-line emission. Useful parameters that can be inferred from observations are the mass-to-flux ratio $M/\Phi$ and the scaling of field strength with density. The former tells us whether magnetic fields exert sufficient pressure to provide support against gravitational contraction; the latter tells whether or not magnetic fields are sufficiently strong to determine the nature (spherical or disk geometry) of the contraction. Examples of massive star formation regions for which detailed observations have been made of magnetic field strengths and morphologies include DR21OH, OMC1, and S106; observational results for these regions and relevant results for the diffuse ISM and masers will be reviewed. Results are that the strength of interstellar magnetic fields remains invariant at $B {\sim} 6\mu$G between 0.1 cm$^{-3} < n(H) < 10^3$ cm$^{-3}$, but increases as $B \propto \rho^{0.4-0.5}$ for $10^3$ cm$^{-3} < n(H_2) < 10^{8}$ cm$^{-3}$. Moreover, $M/\Phi$ is significantly subcritical (strong $B$ with respect to gravity) in diffuse H I clouds that are not self-gravitating, but becomes approximately critical in high-density molecular cloud cores. This suggests that GMCs form primarily by accumulation of matter along magnetic field lines, a process that will increase density but not magnetic field strength. How clumps in GMCs evolve will then depend critically on the $M/\Phi$ ratio in each clump.

Recent years have seen accumulating evidence for infall and rotation around disk like structures toward young stars of spectral types of early B and possibly late O. Observations indicate that the disks or tori are massive in comparison with the mass of the central stars and geometrically thick. Both properties distinguish them from the disks around low mass stars, in particular T-Tauri type stars.

I review observational techniques used in studying disks around massive young stars and summarize properties of disks derived from observations. I will discuss implications of these findings for the formation of massive stars.

The central stars of planetary nebulae represent seemingly well-defined late stages of stellar evolution. Theoretical investigations with predictions of evolutionary tracks impose difficult requirements for observational data. Measurements of spectral energy distributions, of colors, and of magnitudes, and spectroscopic observations are all urgently needed.

Using high-dispersion spectral observations of HD 101065 (Przybylski's star) we have identified the lines of heavy radioactive elements with atomic numbers from 84 to 99 in the spectrum of the star. We found the lines of all these elements except At (Z=85) and Fr (Z=87). We try to explain a presence of such heavy species in the atmosphere of this star as a result of radioactive decay of Th and U nuclei and neutron capture process producing some transuranium isotopes. The necessary conditions for these processes to work may appear due to atomic diffusion and favorable accumulation of the thorium and uranium nuclei in the upper of the PS atmosphere.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Globular clusters produce orders of magnitude more millisecond pulsars per unit mass than the Galactic disk. Since the first cluster pulsar was uncovered 20 years ago, at least 138 have been identified – most of which are binary millisecond pulsars. Because their origins involve stellar encounters, many of the systems are exotic objects that would never be observed in the Galactic disk. Examples include pulsar-main sequence binaries, extremely rapid rotators (including the current record holder), and millisecond pulsars in highly eccentric orbits. These systems are allowing new probes of the interstellar medium, the equation of state of material at supra-nuclear density, the masses of neutron stars, and globular cluster dynamics.

A way of treatment of evolution of common envelope binaries based only on the laws of conservation of energy and angular momentum is suggested. It is shown that the final configuration depends on masses of components and initial period of the system, and on parameters describing friction in the envelope, and mass loss by the system. Possible final stages for massive binaries are either a Thorne-Zytkow type object for initially close binaries or a Wolf-Rayet star in pair with a relativistic compact remnant for wider ones. In the course of disruption of the latter system with orbital periods up to several hours very high space velocity (up to 500 km/s) pulsars can arise.

The study of supermassive galactic black holes (BH) has moved beyond discovery to maturity. The are now ∼ 15 reliable detections. The mass of a central black hole apparently correlates with the mass of the hot component of its galactic host. It may be that every normal galaxy has a supermassive black hole carrying about 10−3 of its bulge mass, with important consequences for the structure and evolution of the core of the galaxy. The most recent major review is by Kormendy & Richstone (1995, KR).

The Local Group contains 37 currently known or probable member galaxies within a radius of 1.8 Mpc (Grebel 1997a). 31 of these galaxies are dwarf galaxies with MB > -17 mag. The most frequent galaxy types are low-mass, gas-poor dwarf spheroidal (dSph) galaxies, which are dominated by old and intermediate-age populations, and more massive, gas-rich dwarf irregular (dIrr) galaxies with recent star formation. DSph galaxies have been found mostly in close vicinity to the large spiral galaxies in the Local Group, while dirr galaxies tend to be more distant and isolated.

Star-disk interaction is thought to drive the angular momentum evolution of young stars. In this review, I present the latest results obtained on the rotational properties of low mass and very low mass pre-main sequence stars. I discuss the evidence for extremely efficient angular momentum removal over the first few Myr of pre-main sequence evolution and describe recent results that support an accretion-driven braking mechanism. Angular momentum evolution models are presented and their implication for accretion disk lifetimes discussed.

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

Standard stellar evolution predicts that F stars should retain their initial surface lithium (Li) abundance because their convection zones are too shallow to destroy it at their base. Yet, observations reveal a severe Li depletion (the “Boesgaard Gap”), perhaps by as much as about two orders of magnitude, in a narrow Teff range. Several physical mechanisms, not usually included in stellar evolution calculations, have been proposed to account for this Li deficiency. These include diffusion, mass loss, meridional circulation, and rotationally-induced mixing driven by angular momentum loss. Identifying which of these (if any) might really be at work is not only of vital interest to stellar evolution, but may also have serious implications elsewhere (e.g. cosmology, Deliyannis et al. 1991). We bring attention to beryllium (Be) observations in F stars, which are crucial for discriminating between scenarios. Particularly important is the star 110 Her, which is depleted in Be by about a factor of 5 -10, but still has a detectable Li abundance (depleted by a factor of 100 - 200). Depleting surface Be without having depleted nearly all of the surface Li requires specific circumstances; we discuss how this depletion property severely constrains or eliminates most of the proposed mechanisms. One mechanism, rotationally-induced mixing, predicts relative depletions for these elements that agree well with what is observed.

We review what species remain to be seen for several types of astrochemistry: Thermochemical Equilibrium (TE) in circumstellar envelopes (CSEs); photo- and ion-molecule chemistry in CSEs; ion-molecule chemistry in cold interstellar clouds; grain chemistry (passive, catalytic, disruptive); and shock chemistry. In CSEs, a rich Si gas-phase chemistry is now recognized, and two predicted species (SiN, SiH2) have been seen. Others are predicted. In the ISM, a global picture of refractory-element chemistry predicts that compounds of Mg, Na, Fe, and possibly Al occur with detectable gas-phase abundance. Predicted species require laboratory synthesis and spectroscopy. Reactions of hydrocarbon ions with neutral species dominate the formation of the families CnH, HCnN, H2Cn, and CnO in both interstellar (TMC-1) and circumstellar (IRC10216) cases, and readily explain the favored values of n in each case as well as predicting which higher-n species remain to be seen. Confirmation of H3O+ (interstellar) is discussed.

We review the present status of our knowledge about observational evidence of the influence of rotation on the evolution and chemical surface enrichment of OB Main Sequence stars. We pay special attention to the CNO elements and show that luminosity class IV-V OB stars provide a good reference point for abundance analyses.

While there is clear evidence of rotationally induced mixing in OB stars, we show that fast rotation is not a guarantee of enrichment. A comparison of observed data with present evolutionary models indicates that the observed facts can be explained assuming that the stars are born with a distribution of rotational velocities, and that depending on the stellar mass the surface abundance changes will be dominated by rotation or mass loss. Only the existence of a large number of B supergiants beyond the Main Sequence cannot be explained in this scenario. We show that current evolutionary models including rotation do not adequately account for the transfer of angular momentum from the interior to the surface.

We point out that the difficulty in determining He abundances and in knowing the present or past binary status of many stars leads us to consider the above conclusions as preliminary.

We present spectroscopic analysis of ∼1000 stars on the Lick, Keck and AAT planet search projects. This analysis provides a quantitative, and unbiased correlation between metallicity and the rate of occurrence of detected gas giant planets with orbital periods shorter than three years. As stellar metallicity increases, the occurrence of planets increases. Stars with [Fe/H] that is one third of solar only have gas giants detected ∼ 3% of the time. Stars with solar metallicity have a planet occurrence rate of 5 − 10%. The occurrence of gas giant planets rises to 20% in stars with a metallicity that is three times solar.

At issue is whether the quantitative dependence of planet occurrence on metallicity is primarily an initial condition, or a by-product of accretion of gas-depleted material onto the convective zone of the star. Accretion could be distinguished as the underlying mechanism for enhanced metallicity if: 1) planet-bearing F-type stars with thinner convective envelopes show a higher mean metallicity than planet-bearing G- or K-type stars, or 2) planet-bearing sub-giants with diluted convective zones showed statistically lower metallicity than their main sequence counterparts.

Non-radial pulsations in isolated white dwarfs have been known for 25 years and it has been shown that the hydrogen-rich (DA) white dwarfs have a high probability of pulsating if they lie in the instability strip with effective temperature between 11500 and 13200 K - the ZZ Ceti stars (e.g. Kepler and Nelan 1993). Analysing techniques developed for such stars allow derivation of masses, luminosities, rotation periods, hydrogen surface layer masses and other properties (e.g. Kepler and Bradley 1995). A number of binary systems are known in which the primary is a white dwarf; dominant in this class are the cataclysmic variable (CV) stars. Until now no CV primary has been found to have non-radial pulsations.

Recent observations of impulsive microwave and hard X-ray emissions during the early phase of the flares are briefly reviewed in order to deduce the dynamics of energetic electrons consistently from two view points of the microwaves and X-rays. An emphasis is put on the necessity of distinction between temporal and spatial variations so far confused in the interpretation of the time histories of the X-ray and radio emissions. The role of plasma turbulence on the dynamics of the energetic electrons is shown to be important in deducing the model of X-ray and radio sources.

Galileo spacecraft data suggest that a global ocean exists beneath the frozen ice surface Jupiter's moon Europa. Since the early 1970s, planetary scientists have used theoretical and observational arguments to deliberate the existence of an ocean within Europa and other large icy satellites. Galileo magnetometry data indicates an induced magnetic field at Europa, implying a salt water ocean. A paucity of large craters argues for a surface on average only ~40-90 Myr old. Two multi-ring structures suggest that impacts punched through an ice shell ~20 km thick. Europa's ocean and surface are inherently linked through tidal deformation of the floating ice shell, and tidal flexing and nonsynchronous rotation generate stresses that fracture and deform the surface to create ridges and bands. Dark spots, domes, and chaos terrain are probably related to tidally driven ice convection along with partial melting within the ice shell. Europa's geological activity and probable mantle contact permit the chemical ingredients necessary for life to be present within the satellite's ocean. Astonishing geology and high astrobiological potential make Europa a top priority for future spacecraft exploration, with a primary goal of assessing its habitability.

The cosmic microwave background (CMB) provides us with our most direct observational window to the early universe. Observations of the temperature and polarization anisotropies in the CMB have played a critical role in defining the now-standard cosmological model. In this contribution we review some of the basics of CMB science, highlighting the role of observations made with ground-based and balloon-borne Antarctic telescopes. Most of the ingredients of the standard cosmological model are poorly understood in terms of fundamental physics. We discuss how current and future CMB observations can address some of these issues, focusing on two directly relevant for Antarctic programmes: searching for gravitational waves from inflation via B-mode polarization, and mapping dark matter through CMB lensing.

The MESSIER surveyor is a small mission designed at exploring the very low surface brightness universe. The satellite will drift-scan the entire sky in 6 filters covering the 200–1000 nm range, reaching unprecedented surface brightness levels of 34 and 37 mag arcsec−2 in the optical and UV, respectively. These levels are required to achieve the two main science goals of the mission: to critically test the ΛCDM paradigm of structure formation through (1) the detection and characterisation of ultra-faint dwarf galaxies, which are predicted to be extremely abundant around normal galaxies, but which remain elusive; and (2) tracing the cosmic web, which feeds dark matter and baryons into galactic haloes, and which may contain the reservoir of missing baryons at low redshifts. A large number of science cases, ranging from stellar mass loss episodes to intracluster light through fluctuations in the cosmological UV-optical background radiation are free by-products of the full-sky maps produced.

Important problems to which we would like to find answers are:

1. • What are the distances to the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC)?

2. • What is the present distribution of stars, gas and dark matter in the Clouds, and how did it evolve?

3. • How, and where, did the Magellanic Clouds form, and how have their orbits evolved?

4. • Finally the recent discovery of numerous microlensing events in the Clouds provides answers to questions that we have only recently started to ask.