The aim of the Round Table (RT) ”Problems in modelling stellar atmospheres“ was that of giving a panoramic view of the state of art on the atmospheric models used to predict observations of stars from T to A spectral type, the Sun included.

It is shown that under certain conditions hydrostatic equilibrium becomes unstable in a conducting medium in the presence of a magnetic field containing a neutral point if the gas pressure is less than a limiting value.

The motion resulting from breakdown of hydrostatic equilibrium in the solar chromosphere above complex sunspot groups could produce solar flares and cosmic ray particles.

The third dredge-up phenomenon in asymptotic giant branch stars, responsible for the formation of C stars, is discussed based on detailed evolutionary model calculations. The structural readjustment of the star as dredge-up proceeds is analyzed, and its consequences on dredge-up predictions discussed. The question of how to obtain dredge-up in asymptotic giant branch models is also addressed. It is stressed, in particular, that the modeling of dredge-up requires some sort of extra-mixing to be applied below the envelope if the local Schwarzschild criterion is used to delimit convective zones.

The study of star formation is a relatively young discipline of the field of astronomy. Up until the mid point of the twentieth century only a most rudimentary understanding of the subject was possible. This is because prior to that time there did not exist any substantive body of empirical data which could be used to critically test even the most basic hypotheses concerning stellar origins. However, as a result of impressive advances in observational technology and in our understanding of stellar evolution during the last forty years, the subject of star formation has developed into one of the most important branches of modern astrophysical research. A large body of observational data and a considerable literature pertaining to this subject now exist and a significant fraction of the international astronomical community devotes their efforts towards trying to comprehend the origins of stars and planets. Yet, despite these efforts we have yet to observationally identify, with any certainty, a single object in the process of stellar birth! Moreover, we have not yet produced a viable theory of star formation, one capable of being tested and refined by critical experiment. In many ways, stellar birth is as much a mystery today as it was forty years ago. However, there can be little doubt that during the last two decades truly revolutionary progress has been made in the quest to understand the star formation process in our galaxy. This apparent paradox in the state of our knowledge concerning stellar origins is resolved with the realization that the history of the study of star formation has been a history of the study of progressively earlier and earlier stages of stellar evolution. Indeed, it is in precisely this area of endeavor that we have learned so much.

The Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory is a fully robotic 0.76-m reflector equipped with a CCD imaging camera. Its telescope control system checks the weather, opens the dome, points to the desired objects, finds and acquires guide stars, exposes, stores the data, and manipulates the data without human intervention. There is a 20-slot filter wheel, including UBV RI. Five-minute guided exposures yield detections of stars at R ≈ 20 mag when the seeing is good (≤2″).

One of our main goals is to discover nearby supernovae (SNe; redshifts generally less than 5000 km s−1), to be used for a variety of studies. Special emphasis is placed on finding them well before maximum brightness. A limit of ~ 19 mag is reached in the 25-sec unfiltered, unguided exposures of our Lick Observatory Supernova Search (LOSS). We can observe over 1200 galaxies in a long night, and we try to cycle back to the same galaxies after 3 to 4 nights. Our software automatically subtracts template images from new observations and identifies supernova candidates that are subsequently examined by student research assistants. LOSS found 20 SNe in 1998, 40 in 1999, and 36 in 2000, making KAIT the world’s most successful search engine for nearby SNe. We also find novae in the Local Group, comets, asteroids, and cataclysmic variables. Multifilter follow-up photometry is conducted of the most important SNe, and all objects are monitored in unfiltered mode. A Web page describing LOSS is at http://astro.berkeley.edu/~bait/kait.html.

Forbush decrease (or, in a broader sense, Forbush effect) - is a storm in cosmic rays, which is a part of heliospheric storm and very often observed simultaneously with a geomagnetic storm. Disturbances in the solar wind, magnetosphere and cosmic rays are closely interrelated and caused by the same active processes on the Sun. Thus, it is natural and useful to investigate them together. Such an investigation in the present work is based on the characteristics of cosmic rays with rigidity of 10 GV. The results are derived using data from the world wide neutron monitor network and are combined with relevant information into a data base on Forbush effects and large interplanetary disturbances.

PN can be divided into four types depending on their chemical composition. In order of decreasing heavy element abundances the types are: I) He and N rich, II) intermediate population, III) high velocity, and IV) halo population. The type II PN are overabundant in N and C relative to the Orion Nebula. Well defined gradients across the galactic disk of He, N and O are derived from type II PN; the oxygen gradient is similar to the metallicity gradient derived from GK giants and F main sequence stars. By comparing the O, Ne and S abundances of PN of types III and IV with the Fe abundances of stars of similar population it is found that the O, Ne and S enrichment in the Galaxy probably took place before the Fe enrichment.

Recent advances in the calculation and measurement of transition probabilities, electron excitation rate coefficients and photoionization cross sections relevant to the study of planetary nebulae are discussed. A compilation of these parameters is also presented.

Due to weather-related travel delays Dr. McCarthy was unable to present his scheduled paper. In his absence, however, Dr. K. Yokoyama, Chairman of the International Earth Rotation Service (IERS), reported on the status of the revision of the IERS Standards carried out by McCarthy who provided the following precis.

These standards are meant to be used in the reduction of observations contributed to the IERS and by those who require IERS estimates of polar motion, Universal Time and nutation to establish the most precise celestial and terrestrial reference systems. The goal of the IERS is to publish the document, an update of the previous version (McCarthy, 1989), in the beginning of 1992.

The effect of gravitational settling and radiation driven diffusion on the evolution of stars near the main sequence is reviewed. New simplified formulae for calculating diffusion are proposed that improve on previous such formulae. The reliability of available diffusion coefficients is discussed and areas where further work is needed are identified. Newly available opacity calculations are used to estimate the effects of radiative acceleration on Fe.

The size of the modifications to the evolution are shown to be modest: a reduction of order 10% on the evolutionary age of globular clusters. There are indications from the Li abundance in the high Teff halo stars that some turbulence is present below the convection zone. Models calibrated using solar properties reproduce the Teff at which the Li gap is observed in F stars as well as its depth without any arbitrary parameter. Similarly the presence of AmFm stars is explained over the Teff range where they are observed.

Some dwarf galaxies have HI rotation curves that are completely dominated by a surrounding dark matter (DM) halo (e.g. Carignan & Freeman 1988). These objects represent ideal candidates for an investigation of the density structure of low-mass DM halos as the uncertainties resulting from the subtraction of the visible component are small, even in the innermost regions. Flores & Primack (1994) and Moore (1994) compared the observed DM rotation curves with the profiles, predicted from cosmological cold dark matter (CDM) calculations. They found an interesting discrepancy: whereas the calculations lead to a DM density distribution which diverges as ρ ∼ r−1 in the inner parts, the observed rotation curves indicate shallow DM cores which can be described by an isothermal density profile with finite central density.

Observed and derived structure parameters are tabulated for 154 galactic globular clusters, 7 dwarf spheroidal satellites of the Galaxy, and 6 globular clusters in the Fornax dwarf spheroidal. Observational parameters listed include equatorial coordinates, apparent level of the horizontal branch, reddening, subgiant branch color at the horizontal branch level, limiting and core angular radii, integrated magnitudes, and central surface brightnesses. Derived parameters include galactic coordinates, heliocentric and galactocentric distance, metallicity, limiting and core radii, central relaxation time scale, central mass density, central velocity dispersion, and central escape velocity.

In the future, the ephemerides produced at JPL will be based upon the reference frame of the radio source catalogues. Recent planetary observations have been made directly with respect to the radio frame, and these observations have shown a satisfying degree of absolute accuracy and internal consistency; they provide an automatic frame-tie.

A workshop on the dynamics, emission and morphology associated with the highly collimated outflows seen in radio galaxies and quasars was held at The University of Alabama in Tuscaloosa in September of 1995. Complete workshop proceedings will be published in the ASP Conference Series. This workshop review covers the theoretical developments and problems discussed at the workshop.

The CoRoT Mission and its performances in flight are summarised. After more than 500 days in orbit, the early results in the exoplanet finding programme are highlighted. The first 5 planets discovered are compared to the previous population of exoplanets.

Recent work on the dynamics of galaxy bulges has been dominated by two themes. (1) Bulges share the richness in kinematic structure that is currently being discovered in elliptical galaxies. This includes kinematic evidence for triaxiality and for accretion (counterrotating gas and stellar components). (2) The main subject of this paper is observational and theoretical evidence that some “bulges” are built secularly out of disk material. Many bulges show photometric and kinematic evidence for disklike dynamics. This includes (i) velocity dispersions σ much smaller than those predicted by the Faber-Jackson σ — M B correlation, (ii) rapid rotation V(r) that implies V/σ values well above the “oblate line” describing rotationally flattened, isotropic spheroids in the V/σ — ellipticity diagram, and (iii) spiral structure dominating the r 1/4 part of the galaxy. In these galaxies, the steep, r1/4-law central brightness profiles belong not to bulges but to disks. That is, some galaxy disks have central brightness profiles that are much steeper than the inward extrapolation of an exponential fit to the outer parts. These observations and n-body simulations of gas flow in nonaxisymmetric galaxies imply that high-central-concentration, flat components can be formed out of disk gas that is transported toward the center by bars and oval distortions. The n-body models suggest further that some “bulges” are built of disk stars heated in the axial direction by resonant scattering off of bars. These effects are signs that important secular evolution processes are at work in galaxy disks.

A young star cluster is a less contrived explanation than a massive black hole for many of the features seen in the Galactic center. However from a Copernican point of view, this explanation is less attractive than a black hole. The evidence for a ~ 106M⊙ black hole is becoming progressively less convincing, but the case against it is no stronger. We describe the development of a singular star cluster, as well as the processes of stellar disruption, merging, and gas accretion in such a cluster. Recently merged stars and tidally stripped giants may be detectable within an arcminute of the Galactic Center. We examine the physics of star formation in the inner parsecs of the galaxy, and the problem of maintaining the two parsec molecular torus.

There are point-like sources in central regions of several supernova remnants which have not been detected outside the X-ray range. The X-ray spectra of these Central Compact Objects (CCOs) have thermal components with blackbody temperatures of 0.2–0.5 keV and characteristic sizes of 0.3-3 km. Most likely, the CCOs are neutron stars born in supernova explosions. We overview their observational properties, emphasizing the Chandra data, and compare them with magnetars.

20 years of CORAVEL photoelectric radial-velocity measurements associated with the high precision achieved by the ELODIE spectrograph on a fair time span allow us to propose a new list of high-precision radial-velocity standards with velocity variations lower than a few times 10 m s−1.