The segregated disk populations obtained from applying the MEMPHIS algorithm (Cubarsi & Alcobé, This symposium) to the Hipparcos catalogue are the basis of the following important kinematical results (Cubarsi & Alcobé 2006). In particular, the thick disk population was extrapolated until reaching an asymptotic ideal axisymmetric population. The obtained no net radial motion point had a radial heliocentric velocity of 20 ± 1 Km s−1 toward the galactic anticentre, which is the opposite of the solar radial motion.

According to the obtained population mean velocities, an intriguing question arose: Why the young thin disk population, the continuum of old thin disk stars, and the thick disk, are moving, on average, in the same direction, as belonging to an unique main stream? On the other hand, the early thin disk population, in the region of the Hyades-Pleiades supercluster, remains as an isolated population, with a nearly null radial mean velocity.

The thick disk stars drawn from increasing Hipparcos subsamples showed a decreasing trend of vertex deviation (Cubarsi & Alcobé 2004, Alcobé & Cubarsi 2005), by indicating a clear trend to axial-symmetry. If we assume that the asymptotic thick disk is nearly in steady state, then we can also admit a null radial mean velocity for the oldest thick disk. Thus, in the plane, using galactocentric cylindrical coordinates, with star velocities Π (toward the Galactic anticentre) and Θ (in the rotational direction), the mean velocity of thick disk stars satisfieswhere Π0(cyl) and Θ0(cyl) are the mean velocities of a pure axial population, and ρ is a constant.

The rotation mean velocity of such an ideal axial and steady state thick disk was extrapolated for Π0=Π0(cyl)=0, giving a value of Π0(cyl) = 138 ± 2 Km s−1. Moreover, the progressive partial thick disk populations were also extrapolated in the Π Θ plane, up to the above rotation mean velocity, leading to a solar galactocentric radial velocity of Π⊙ = −20 ± 1 Km s−1.

The centroid of such an asymptotic local thick disk (or local halo) is moving on a circular orbit, similarly to the early-thin disk. The young-thin disk is moving on the most eccentric elliptical orbit. This fact would be consistent with the effect of a Galactic bar moving stars from circular to eccentric orbits, in the journey from the early to the young thin disk. As the stars get older, the disk populations partially lose their average angular momentum, as well as they lose radial motion and increase their velocity dispersion.

Finally, let us remark that the mean radial velocity of the thick disk stars remains explained as the addition of a term due to the non axiality of the system, and a term due to the system's time dependence, which is clearly non-null. Both terms are acting in opposite senses, and are more important for younger than for older stars. The term due to the deviation from axial symmetry increases the radial motion toward the Galactic center, while the time dependent term opposes it, in a trend to recover the axial symmetry, that is reached for the extrapolated population.

Observations of Sgr A* over the past 4 years with the Keck Telescope in the near-infrared, coupled with millimeter and submillimeter observations, show that the 3.7×106M⊙ Galactic Black Hole, Sagittarius A*, displays continuous variability at all these wavelengths, with the variability power concentrated on characteristic time scales of a few hours, and with a variability fraction that increases with wavelength. We review the observations indicating that the few-hour time scale for variability is reproduced at all accessible wavelengths. Interpreted as a dynamical time, this time scale corresponds to a radial distance of 2 AU, or ∼25 Schwarzschild radii. Searches for quasi-periodicities in the near-infrared data from the Keck Telescope have so far been negative. One interpretation of the character of these variations is that they result from a recurring disk instability, rather than from variations in the mass accretion rate flowing through the outer boundary of the emission region. However, neither a variable accretion rate nor a mechanism associated with a jet can presently be ruled out.

We present observations of the dusty emission from the young planetary nebulae Hen 2-113 and CPD-56$^\circ$8032 obtained with VLT/NACO, VLTI/MIDI. Our NACO observations of Hen 2-113 reveals the presence of a diabolo-shaped structure. The L$\prime$ and M$\prime$ flux from the central source, show a strong infrared excess close to the central star and this source is resolved at a scale of about 150 mas. This infrared excess is explained by emission from a cocoon of hot dust with mass $\sim 10^{-9}$ M$_{\odot}$ at $\sim$900 K. The central source is no longer visible with MIDI in the N-band and the nebula is fully resolved by a 8m telescope in this band. The dusty environment of CPD-56$^\circ$8032 is much more compact, dominated by a bright, barely resolved, core whereas visible unpublished HST images shows that the nebula has an amazing complexity. From MIDI 8.7-$\mu$m acquisition images (dominated by PAH emission), the extension and geometry of the core have been estimated. Moreover, high SNR fringes at low level have been detected with projected baselines between 40 and 45 meters. This clear signal is interpreted in terms of the bright inner rim of a dusty disk exposed to the flux from the Wolf-Rayet star. The geometrical parameters of the N-band flux distribution are well constrained by means of simple geometrical models and a simple radiative transfer model has been developed to extract the physical parameters of the disc. The PA angle of the disk agrees well with the HST/STIS observations of De Marco et al. (2002), but the inferred inclination is much less (i$\,{\sim}\,30^\circ$).

We propose that the most massive stars in the local Universe start out on the main sequence being extremely luminous and already exhibiting wind-like emission lines. Such stars can probably be identified as hydrogen-rich WN5-7 stars. Masses are now being determined for these stars using the least model-dependent technique of binary orbits.

In this paper, we have presented high resolution magnetograms around sunspot at CaI $6102.7 \AA$ photospheric line and in $H\alpha$ chromospheric line.

Futher, more the longitudinal magnetic field difference in two wings(red and blue)around central line in photosphere and chromosphere has been studied.

Using a huge library of 1-Å resolution spectra over a wide range of log Teff, log g and [Fe/H] and for both solar and α-enhanced abundance ratios [α/Fe], we derive the response functions (s) which are commonly used to correct indices with solar α-enhanced ratios to indices with α-enhanced>0. The s vary not only with the type of star but also with metallicity. With the aid of this and the fitting functions (s), we derive the indices for single stellar populations. The new indices for single stellar populations are used to derive the age, metallicity, and degree of enhancement first for sample of Galactic globular clusters for which these key parameters have been independently derived from the colour-magnitude diagram and/or spectroscopic studies, and second to study the classical two index diagram.

The current status of microturbulent velocity and abundance determinations for A and F dwarfs in open clusters is reviewed. A programme to observe several tens of A and F dwarfs in open clusters of various ages was initiated several years ago. We have performed high resolution high signal-to-noise spectroscopy of stars well distributed in mass along the Main Sequence. Microturbulent velocities and abundances of several chemical elements have been derived iteratively by fitting grids of synthetic spectra calculated in LTE to the observed spectra. Curve of growths were used in a few instances as well. The results obtained are reviewed for Coma Berenices, the Pleiades, Alpha Persei and the Ursa Major moving group.

The microturbulent velocities exhibit a broad maximum in the range A5V to about F0V as indicated in Smalley (2004).

Using radial velocities of vibrationally excited H2 emission in OMC1 we present the structure functions and the scaling of the structure functions with their order at scales ranging from 70 AU to 30000 AU extending earlier related studies to scales lower by two orders of magnitude. The structure functions for OMC1 show clear deviations from power laws at 1500 AU. The scaling of the higher order structure functions with order deviates from predicted theoretical scalings. Observational results are compared with simulations of supersonic hydrodynamic turbulence. The unusual scaling is explained as a selection effect of preferentially observing the shocked part of the gas. The simulations are unable to reproduce the deviations from power laws of the structure functions.

Pre-encounter ground-based thermal observations of NEA 25143 Itokawa at 10μm led to a size prediction of 520(±50) × 270(±30) × 230(±20)m, corresponding to an effective diameter of DTPMeff= 318m (Müller et al.2005). This is in almost perfect agreement with the final in-situ results 535 × 294 × 209m (DHayabusaeff= 320m; Demura et al.2006). The corresponding radar value, based on the same shape model (Kaasalainen et al.2005), were about 20% too high: 594 × 320 × 288m (DRadareff= 379m; Ostro et al.2005). The very simple N-band observations revealed a surface which is dominated by bare rocks rather than a thick regolith layer. This prediction was nicely confirmed by the Hayabusa mission (e.g., Fujiwara et al.2006; Saito et al.2006). The ground-based measurements covered three different phase angles which enabled us to determine the thermal properties with unprecedented accuracy and in excellent agreement with the results from the touch-down measurements (Okada et al.2006; Yano et al.2006). These thermal values are also key ingredients for high precision Yarkovsky and YORP calculations (mainly the rotation slowing) for Itokawa (e.g., Vokrouhlický et al.2004; Vokrouhlický et al.2005). In addition to the above mentioned properties, our data allowed us to derive the surface albedo and to estimate the total mass. We believe that with our well-tested and calibrated radiometric techniques (Lagerros 1996,1997,1998; Müller & Lagerros 1998, 2002; Müller 2002) we have tools at hand to distinguish between monolithic, regolith-covered and rubble pile near-Earth objects by only using remote thermal observations. This project also emphasizes the high and so far not yet fully exploited potential of thermophysical modeling techniques for the NEA/NEO exploration.

Hasan et al. (2005) have recently presented 2-D dynamical calculations on wave propagation in in the magnetic network of the Sun. The latter is idealized as consisting of non-potential flux tubes in the quiet solar chromosphere. It is of interest to understand how the nature of wave propagation is influenced by the choice of initial equilibrium configuration of the magnetic field. We examine this by comparing the earlier calculations with those when the network is modelled as a potential structure. Our calculations demonstrate that the nature of the wave propagation is significantly different, particularly the transport of energy which for the potential case, occurs more isotropically than for the non-potential configuration.

One of the most important changes in observational astronomy of the 21st Century is a rapid shift from classical object-by-object observations to extensive automatic surveys. As CCD detectors are getting better and their prices are getting lower, more and more small and medium-size observatories are refocusing their attention to detection of stellar variability through systematic sky-scanning missions. This trend is aditionally powered by the success of pioneering surveys such as ASAS, DENIS, OGLE, TASS, their space counterpart Hipparcos and others. Such surveys produce massive amounts of data and it is not at all clear how these data are to be reduced and analysed. This is especially striking in the eclipsing binary (EB) field, where most frequently used tools are optimized for object-by-object analysis. A clear need for thorough, reliable and fully automated approaches to modeling and analysis of EB data is thus obvious. This task is very difficult because of limited data quality, non-uniform phase coverage and solution degeneracy. This paper reviews recent advancements in putting together semi-automatic and fully automatic pipelines for EB data processing. Automatic procedures have already been used to process Hipparcos data, LMC/SMC observations, OGLE and ASAS catalogs etc. We discuss the advantages and shortcomings of these procedures.

In this paper the basic researches, telescopes and devices of the Khurel Togoot astronomical observatory, which was founded during the International Geophysical Year, are briefly described. Our astronomical observatory is located on Bogd Mountain near the capital city Ulaanbaatar. Almost 50 years of scientific work has been carried out there. In particular, astrometric researches, GPS, solar researches and observations of minor planets are conducted. Now these scientific researches basically are maintained and extended, with the introduction of modern technology. As an example of the data received by our solar telescope ‘Coronagraph’, some solar images will be shown. Recently we equipped this telescope with a CCD camera. Because of the transformation of the economy in Mongolia, there are at present difficulties with the preparation of young professional astronomers and with the purchase of new astronomical equipment.

Molecular line emission in the mm- and submm-wave domains is found to be a very useful tool to study planetary nebulae (PNe). Molecular lines, particularly the low-$J$ transitions of carbon monoxide, are known to probe most of the nebular material in young PNe and protoplanetary nebulae (PPNe). Many quantitative results on these objects have been so obtained, including general structure, total mass and density distribution, kinetic temperatures, velocity fields, etc. In more evolved PNe, however, the molecular line intensity (or even detection) is quite uncertain, due to photodissociation. Molecular lines often trace just certain parts of these nebulae, like equatorial tori or axial clumps. Other molecules are in general more affected by photodissociation than CO, but photo- or shock-induced chemistry produces high abundances of radicals and large molecules in some intermediate-evolution objects. The presence of rotating disks in some objects is finally discussed.

The process of cataloguing the minor planet population of the Solar System has experienced a great advance in the last decades with the start-up of several surveys. The large volume of data generated by them has increased with time and given rise to huge databases of asteroids with uneven qualities.

In fact, a significant fraction of these objects have not been enough observed, thus leading to the computation of very poor quality orbits as to carry out useful predictions of the positions of such asteroids. As a result, some objects can get lost, which is particularly embarrassing for those with Earth crossing orbits.

When this situation persists for a long time, the aforementioned databases end up contaminated in the sense that they contain more than one discovery for the same physical object and some kind of action must be taken. The algorithms for asteroid identifications are thought precisely to mitigate this problem and their design will depend upon the quality of the available data for the objects to be identified.

In this paper we will distinguish two cases: when both objects have a nominal orbit and when one of them lacks it. In addition, when the available data poorly constrain the solution, other orbits in the neighbourhood of the nominal one are also compatible with the observations. Using these alternative orbits allows us to find many identifications that otherwise would be missed. Finally, we will show the efficiency of all these algorithms when applied to the datasets distributed by the Minor Planet Center.

I discuss how galaxy fundamental parameters that are derived by comparing observational data with stellar population models, depend on the adopted models. The emphasis is on the treatment of the Thermally-Pulsing Asymptotic Giant Branch (TP-AGB) stellar phase, that is a source of major discrepancy between the various model renditions. In particular, I show that ages and stellar masses of galaxies decrease when models including an empirically-calibrated TP-AGB phase are considered. Illustrative examples are provided for a wide redshift range. Constraints to galaxy formation models need revision on the light of these results.

Masses, radii and luminosities of distant stars can only be measured accurately in eclipsing binaries. The most massive eclipsing binary currently known is WR 20a, which consists of two ~ 80 M⊙ stars in a 3.7 d orbit. Analogs of WR 20a are bound to exist both in massive stellar clusters in our Galaxy and in nearby galaxies. The nearest ones are located in the clusters near the Galactic Center: the Center, Arches, and Quintuplet clusters. The severe amount of reddening in the galactic disk makes the study of galactic clusters challenging. However, with current 8-m class telescopes, the study of massive stars in nearby galaxies is also feasible. The nearest Local Group galaxies (LMC, SMC, M 31, M 33) provide the perfect laboratory for studying massive stars and determining their properties as a function of metallicity. Such studies will constrain models, confirm the dependence of evolution on metallicity and help understand the rate and nature of supernovae and gamma-ray bursts.

In this work, we investigate the dynamical influence that external, triaxial and tumbling halos may exercise on disks that may lie embedded in them. Such halo configurations are noted in cosmological simulations, to typically rotate about their short axes, with tumbling periods of the order of a Hubble time. Thus, such halos can exert a slowly changing external torque on disks, affecting disk evolution in the process. Another source of complex dynamical effects is the probable misalignment between a disk and a triaxial dark halo. In this work, we conduct a series of experiments in which we explore the effect of a slowly changing quadrupolar tidal potential on N-body models of our Galaxy and M31; our particular aim is to check if this can induce disk structures such as bars, spirals and warps!

Extremely red objects were identified in the early Spitzer Space Telescope observations of the bright-rimmed globule IC 1396A; they were classified as Class I protostars Class II T Tauri stars with disks based on their colors. New spectroscopic observations covering 5.5–38 μ confirm this identification. The Class I sources have extremely red continua, still rising at 38 μm, with a deep silicate absorption at 9–11 μm, weaker silicate absorption around 18 μm, and weak ice features including CO2 at 15.2 μm and H2O at 6 μm. The Class II sources have warm, luminous disks, with a silicate emission feature at 9–11 μm. Optical spectra with the Palomar Hale 200-inch telescope show the Class II sources to be actively accreting, classical T Tauri stars with bright Hα and other emission lines. The Class I sources are located within the molecular globule, while the Class II sources are more widely scattered. This suggests two phases of star formation occurred in the region, the first one leading to the Class II sources including LkHα 349a, c that are located in the center of the globule, and a very recent one (less than 100,000 yr ago) that is occurring within the globule. This second phase was likely triggered by the wind and radiation of the central O star of the IC 1396 H II region, with possible additional contributions from the outflows of LkHα 349a, c and some nearby B stars.

We study a possibility of tidal disruptions of stars orbiting a supermassive black hole due to eccentricity oscillations driven by Kozai's mechanism. We apply the model to conditions relevant for the Galactic Centre where we consider two different sources of the perturbation to the central potential, which trigger the resonance mechanism. Firstly, it is a disc of young massive stars orbiting Sgr A* at r ≳ 0.08 pc, and, secondly, a molecular circumnuclear disc. Each of the two possibilities appears to be capable of exciting eccentricities to values sufficient for the tidal disruption of ∼100 stars from the nuclear stellar cluster on a time-scale of 0.1–10 Myrs. Tidally disrupted stars may cause periods of increased accretion activity of Sgr A*.