New determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described. The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.

We provide a brief overview of some key issues that came out of the IAUS 256 symposium on the Magellanic System (http://www.astro.keele.ac.uk/iaus256).

Using the circumstellar envelope parameters (mean temperature, extent and opacity) derived by fitting theoretical energy distributions to those observed in a sample of 20 Be stars, we estimate the respective magnitude difference ΔV = V – V* of the continuum flux excess produced by their circumstellar envelopes. Using then the HIPPARCOS parallaxes of these stars and the ISM E(B-V) colour excesses derived with the surrounding normal B stars, we estimate the visual absolute magnitude of the central objects in the program Be stars. In most cases the results obtained are in good agreement with the absolute magnitudes obtained from the photospheric (λ1, D) components derived in the BCD spectrophotometric system. There are, however, strong discrepancies in 4 program stars which deserve further studies. The magnitude excess seems to be ΔV ≲ 0 for the higher effective temperatures only. There is no correlation between ΔV and Vsin i, as would be expected if the circumstellar envelopes were strongly flattened.

We report the Suzaku follow-up observations of the Gamma-ray pulsars, 1FGL J0614,13328, J1044.55737, J1741.82101, and J1813.31246, which were discovered by the Fermi Gamma-ray observatory. Analysing Suzaku/XIS data, we detected X-ray counterparts of these pulsars in the Fermi error circle and interpreted their spectra with absorbed power-law functions. These results indicate that the origin of these X-ray sources is non-thermal emission from the pulsars or from Pulsar Wind Nebulae (PWNe) surrounding them. Moreover we found that J1741.82101 exhibits a peculiar profile: spin-down luminosity vs flux ratio between X- and gamma-rays is unusually large compared to usual radio pulsars.

Searching for globular cluster candidates in nearby galaxies such as M31 is the first step to study the characteristics of extragalactic globular cluster systems. Previous searches for M31 globular clusters were mostly based on visual inspection of photograpic plates. We have selected globular cluster candidates from a wide-field Washington CCD survey of M31, using various methods: color-magnitude diagrams, color-color diagrams, point spread function subtraction and visual inspection of the objects. The efficiency and accuracy of these methods for finding globular clusters are presented.

X-ray emission from spiral galaxies without activity is thought to consist of low-mass X-ray binaries (LMXBs), and the Einstein observations established the relation between X-ray (0.2-4 keV) and optical luminosities as log(LX/LB) ~ −4 (Fabbiano, 1992). This relation has been used when discussing the activity other than LMXBs (Iyomoto, 1996). However, spectral information of Einstein Observatory was rather poor above 3 keV, where LMXBs would emit significant energy flux. Therefore we performed ASCA observations of two normal spirals, NGC2903 and NGC628, in order to better calibrate the LX - LB relation.

The Be phenomenon, i.e. the ejection of matter from Be stars into a circumstellar disk, has been a long lasting mystery. In the last few years, the CoRoT satellite brought clear evidence that Be outbursts are directly correlated to pulsations and rapid rotation. In particular the stochastic excitation of gravito-inertial modes, such as those detected by CoRoT in the hot Be star HD 51452, is enhanced thanks to rapid rotation. These waves increase the transport of angular momentum and help to bring the already rapid stellar rotation to its critical value at the surface, allowing the star to eject material. Below we summarize the recent observational and theoretical findings and describe the new picture of the Be phenomenon which arose from these results.

The construction of all age indicators consists of certain basic steps which lead to the identification of the properties desirable for stellar age indicators. Prior age indicators for main sequence field stars possess only some of these properties. The measured rotation periods of cool stars are particularly useful in this respect because they have well-defined dependencies that allow stellar ages to be determined with ~20% errors. This method, called gyrochronology, is explained informally in this talk, shown to have the desired properties, compared to prior methods, and used to derive ages for samples of main sequence field stars.

We investigate the influence of blending on the Cepheid distance scale using two Local Group galaxies, M31 and M33. Blending leads to systematically low distances to galaxies observed with the HST, and therefore to systematically high estimates of H0. High-resolution HST images are compared to our ground-based data, obtained as part of the DIRECT project, for a sample of 22 Cepheids in M31 and 102 Cepheids in M33. For a sample of 22 Cepheids in M31, the average (median) flux contribution from luminous companions not resolved on the ground-based images in the V-band, SV, is about 19% (12%) of the flux of the Cepheid. For 102 Cepheids in M33 the average (median) values of SV, SI, SB are 23% (13%), 28% (20%), 28% (15%). For 64 Cepheids in M33 with periods in excess of 10 days the average (median) SV, SI, SB are 16% (7%), 23% (12%), 20% (10%).

Imaging of active regions in continuum around 1.6 μm shows that many facular regions are less bright than the photosphere when observed nearer to disk center than μ = cos θ ~ 0.75. The contrast of these dark faculae increases with magnetic flux above a threshold of approximately 2 × 1018 Mx. This explains why not all faculae are dark at 1.6 μm, since the magnetic flux density in many regions of bright Ca K plage emission falls below this threshold. After correction for blurring, the typical contrast value is about 4-5%, so the brightness temperature deficit is about 130 K. Faculae are brighter than the photosphere at 1.63 μm nearer to the limb than μ ~ 0.5. The negative contrast of dark faculae may arise from cooling of the surrounding photosphere, or from increased visibility of cool layers of the facular flux tube itself. Quantitative comparison of these IR data with MHD models awaits calculation of flux tube contrasts at realistic angular resolution.

The problem of determining the distance scale for planetary nebulae (PN) is approached through the kinematics of this subpopulation in the galaxy. To this end, we have compiled a catalogue of all known radial velocities for 457 galactic PN with standardized error statistics. External (calibration?) errors of the same magnitude as internal spectral line deviations are noted.

In this work, we study the feasibility of four physical mechanisms for driving jet/disk precession in the galaxies NGC 4258, NGC 1068, 3C 120, OJ 287 and Arp 102B. Given the many observational uncertainties that still exist in the parameters of those AGN, we find that it is difficult to discriminate unambiguously what mechanism is actually responsible for precession.

Accretion from many small planetesimals to planets is reviewed. Solid protoplanets accrete through runaway and oligarchic growth until they become isolated. The isolation mass of protoplanets in terrestrial planet region is about 0.1-0.2 Earth mass, which suggests giant impacts among the protoplanets in the final stage of terrestrial planet formation. On the other hand, the isolation mass in Jupiter's and Saturn's orbits is about a few to 5 Earth masses, which may be massive enough to trigger gas accretion onto the cores. The isolation mass in Uranus and Neptune's orbits is as large as their present cores. Extending the above arguments to extrasolar planetary systems that are formed from disks with various initial masses, we also discuss diversity of extrasolar planetary systems.

We present new observations in the radio continuum of 31 planetary nebulae at 5 and 8 GHz with the Australian Telescope Compact Array. The observations are used to invesigate properties of the interstellar extinction toward Galactic Bulge.

Oscillation frequencies were determined for a number of rapidly rotating main sequence stars. However, real seismic probing is still ahead of us. I review here tools that we have for modeling pulsation in rotating stars and their potential application to seismic sounding.

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 previous reports by Lüst and by Pottasch concerned quasi-stationary mass loss. The loss is called quasi-stationary because the basic characteristics of a star, its temperature and its radius, do not change significantly during the time that a particle needs to flow from the stellar surface out to a point where the stellar influence is negligible. However there are many stars which show significant changes of temperature and radius within a short time. Very often these changes are accompanied by instantaneous ejection of a great amount of material. For example, during the outburst of a nova the ejected mass can reach 10−4M⊙. Such effects are very appreciable in the so-called ‘eruptive variables’, in which the brightness changes spasmodically. It is very likely that the rate and the mechanism of mass loss of eruptive variables are different from that of normal stars.

The OH/IR stars evolving on the Asymptotic Giant Branch are large-amplitude variable stars with periods in the range of ~400 to 2500 days, significantly longer than those of the related Mira variables. We use preliminary results from a monitoring program of the 1612-MHz OH maser variations of a sample of > 70 OH/IR stars to study a possible extension of Mira Period-Luminosity Relations to longer periods. The period distribution of the sample is split around P ~ 1100 days. Using WISE W3 absolute magnitudes as proxies for the luminosity and the best available distances, we found no convincing relation between periods and absolute magnitudes. A cause could be rapid evolution of the ‘extreme OH/IR stars’ (the group with P >1100 days) close to the tip of the AGB, where no increase of luminosity is expected on the short time-scales involved.