The goal of this work is to present an analysis of the observational projects developed by the Teaching and Popularization Section of the Liga Ibero-Americana de Astronomía (LIADA). The Section is based in Brazil and counts on the support of 16 volunteer coordinators from most Latin-American countries. The observational projects are described on the home page of LIADA and aim to attract the attention of the general public, teachers and students to encourage their active participation in observational astronomy. The strategy is to circulate support material and open a discussion forum about each of the astronomical phenomena to enhance their consideration by and visibility to the public. Participants' reports are posted on the Internet forum and the web page of LIADA. We have analyzed the records of these activities and present an evaluation of the difficulties with written reports, the need of a dynamic maintenance of the home page, the establishment of a useful communications network and the visibility of the activities of LIADA.

We report on the discovery of a supermassive binary black-hole (SBBH) system in the radio galaxy 0402+379, with a projected separation between the two black holes of just 7.3 pc. This is the most compact SBBH pair yet imaged by more than two orders of magnitude. These results are based upon multi-frequency imaging using the Very Long Baseline Array (VLBA) which reveal two compact, variable, flat-spectrum, active nuclei within the elliptical host galaxy of 0402+379. Multi-epoch observations from the VLBA also provide constraints on the total mass and dynamics of the system. The two nuclei appear stationary while the jets emanating from the weaker of the two nuclei appear to move out and terminate in bright hot spots. The discovery of this system has implications for the number of compact binary black holes that might be sources of gravitational radiation. The VLBI Imaging and Polarimetry Survey (VIPS) currently underway should discover several more SBBHs.

PNe display a variety of large and small-scale structures which have been the object of a large number of observational and theoretical studies in the last two decades. This review contains a brief description of the different observational approaches used to determine the structure of PNe, and some critical discussion about the morphological components whose formation we believe we understand, and those which instead are still poorly understood.

We study a complete and distance-limited sample of 25 LINERs, 21 of which have been imaged with the Hubble Space Telescope to study their physical properties and to compare their radio and optical properties with those of other samples of local AGNs, namely Seyfert galaxies and low-luminosity radio galaxies (LLRG). Our results show that the LINERs population is not homogeneous, as there are two subclasses: i) the first class is similar to LLRG, as it extends the population of radio-loud nuclei to lower luminosities; ii) the second is similar to Seyferts, and extends the properties of radio-quiet nuclei towards the lowest luminosities. The different nature of the various classes of local AGN are best understood when the fraction of the Eddington luminosity they irradiate, Lo/LEdd, is plotted against the nuclear radio-loudness parameter: Seyferts are associated with relatively high radiative efficiencies Lo/LEdd ≳ 104 (and high accretion rates onto low mass black holes); LLRG are associated with low radiative efficiencies (and low accretion rates onto high black hole masses); all LINERs have low radiative efficiency (and accretion rates), and can be radio-loud or radio quiet depending on their black hole mass.

Although not one red dwarf can be seen with the naked eye, they dominate the solar neighborhood, accounting for no less than 70% of all stars. The large numbers of these wee denizens of the night actually translate into a surprisingly large amount of mass – in fact, more mass is found in M dwarfs than in any other stellar spectral type.

To determine just how important red dwarfs are to the nature of the Universe, an accurate mass-luminosity relation (MLR) must be determined so that a relatively easily determined characteristic, luminosity, can be converted into the critical parameter, mass. Results from a decade-long observational effort to calibrate the MLR for red dwarfs using the Fine Guidance Sensors (FGSs) on the Hubble Space Telescope (HST) will be highlighted. For many of the binary systems targeted, the interferometric data from HST are combined with radial velocity data to further improve the mass measurements, which often have errors less than 5%. Related results from a large southern sky parallax program to determine accurate distances to red dwarfs, and a search for companions orbiting them, will also be discussed.

The state of mass determinations for M dwarfs' smaller cousins, the L and T dwarfs, will also be reviewed. Although we do not yet know the size of the true population of these (primarily) substellar objects, only by mapping out the interplay of their masses and luminosities (which change drastically with time) can we understand their contribution to the mass budget of the Universe.

The problem of isotropization of energetic protons in the $H_\alpha$ emitting region during flare energy release is considered. It has been shown that absence of the linear polarization of $H_\alpha$ emission in some events can be caused by excitation of small scale Alfven waves by anisotropic protons. Consequences of the proposed model are discussed.

Brown dwarf atmospheres are largely convective. These convective gas flows collide and feed back a whole spectrum of turbulent fluctuations into the atmospheric fluid field. Resulting non-static density and temperature fields influence the local chemistry concerning gas phase and dust formation. Numerical simulations are used to show the large and inhomogeneous changes of the gas phase chemistry in a turbulent dust forming cloud region of a brown dwarf atmosphere. The relaxation time scale of the gas phase composition towards steady state is considerably longer than for the dust component.

First I discuss the dynamics of core formation in two scenarios relevant to triggered star formation, namely the fragmentation of shock-compressed layers created by colliding turbulent flows and the fragmentation of shells swept up by expanding nebulae. Second I discuss the influence of thermodynamics on the core mass spectrum, on determining which cores are ‘pre-stellar’ (i.e. destined to spawn stars) and on the minimum mass for a pre-stellar core. Third, I discuss the properties of pre-existing cores whose collapse has been triggered by an increase in external pressure, and compare the results with observations of collapsing pre-stellar cores and evaporating gaseous globules (EGGs).

Small aperture (<1m, typically 20–50 cm) optical telescopes with adequate back-end instrumentation (e.g. photometer, CCD camera and CCD spectrograph) can be used for spreading the joy and excitement of observational astronomy among postgraduate and research students in colleges and universities. On the basis of our experience over a decade of observing with small optical telescopes it has been amply demonstrated that such a facility, which any university can hope to procure and maintain, can be effectively used for teaching and research. The Physics Department of Pt. Ravishankar Shukla University at Raipur, India offers Astronomy & Astrophysics as one of the specializations of its MSc program in Physics. A set of observational exercises has been incorporated with a view to provide training in observations, analysis and interpretation of astronomical data. Observing facilities available in the department include 8”–14” aperture telescopes equipped with a photometer, CCD camera and a CCD spectrograph. A facility of this kind is ideally suited for continuous monitoring of a variety of variable stars, and thus can provide valuable data for understanding the physics of stellar variability. This is especially true for a class of variable stars known as chromospherically active stars. The stars belonging to this class have variable light curves that change from year to year in a rather strange way. A large fraction of these active stars are bright; hence the importance of small aperture telescopes for collecting much-needed photometric data. For over a decade the research activity using the 14” optical telescope has focused on photometric monitoring of well known and suspected active stars. These data, together with X-ray and radio data from archives as well as spectroscopic data obtained at Indian observatories, has led to the identification of new chromosperically active stars. This paper is aimed at sharing our experiences with the colleagues from the developing world on the usage of small optical telescopes for teaching and research with the objective of spreading the joy of astronomy among young students.

The discovery of an excess of light in the far-ultraviolet (UV) in 1969 in elliptical galaxies was a major surprise. While it is now clear that this UV excess (UV-upturn) is probably caused by an old population of helium-burning stars. Han et al. (2002, 2003) proposed a binary model for the formation of hot subdwarfs (helium burning stars) and the model can reproduce the observations in our Galaxy. By applying the binary model to the study of evolutionary population synthesis, we have obtained an a priori model for the UV-upturn of elliptical galaxies. The model shows that the UV-upturn is most likely resulted from binary interactions and it is universal (not very much metallicity-dependant) in ellipticals. This has major implications for understanding the evolution of the UV-upturn and elliptical galaxies in general; contrary to previous postulates, it implies that the UV-upturn is not a sign of age, but could be a potentially powerful indicator for a recent minor burst of star-forming activity.

Chinese scientists have contributed many research works to the field of asteroid surveying and related topics. In the early 1960s, Purple Mountain Observatory (PMO) began observing asteroids and found over 130 new numbered asteroids during the following decades. The Schmidt CCD Asteroid Program (SCAP) of Beijing Astronomical Observatory (BAO) started in 1995 and found 575 asteroids in several years.

NEOs represent a great threat to the near-Earth environment by closely approaching Earth or even impacting with Earth. After the impact of comet SL9 on Jupiter, Chinese proposed to build a NEO Search Telescope to take part in the joint international NEO survey. It is a 1.0/1.2 m Schmidt telescope with a 4K×4K drift scanning CCD detector. Here we elaborate upon its applications to objects of scientific interest, its parameters, and its observing station.

We review the properties of massive Population III and very metal-poor stars, including briefly their formation, IMF, their main sequence evolution, possible mass loss mechanisms, atmosphere modeling etc. For detailed predictions concerning the properties of these stars we refer to Schaerer (2002) and Schaerer (2002) and references therein. Extending these calculations, Schaerer (2007) present new calculations concerning the ionizing power, Ly-α strength and related properties for different metallicities as well as for a range of power-law and log-normal IMFs. For illustrations from these studies see the Figures below. New detailed calibrations for solar metallicity O-type stars have recently been presented by Martins et al. (2005).

We present preliminary analysis of an imaging survey of non-barred ringed galaxies (NBRGs). We have taken broadband, narrow band, and spectroscopic data for a sample of NBRGs selected from the Third Reference Catalogue of Bright Galaxies and the Catalogue of Southern Ringed Galaxies. These galaxies are the subject of a survey in order to (1) better understand the mode of ring formation in the absence of a strong bar and (2) delineate the general photometric and spectroscopic properties of this group as a whole.

Loosely bound, fragile binary stars, whose separations may reach ∼ 0.1 pc, are like open clusters with two coeval components. They provide a largely overlooked avenue for the investigation of many astrophysical questions. For example, the orbital distribution of fragile binaries with two long-lived main-sequence components provides a sensitive test of the cumulative effects of the Galactic environment. In pairs where one component is evolved, the orbits have been amplified by post-main-sequence mass loss, potentially providing useful constraints on the initial-to-final mass relation for white dwarfs. The nearly featureless spectra of cool white dwarfs usually provide little information about intrinsic radial velocity, full space motion, population membership, metallicity, etc. However, distant main sequence companions provide benchmarks against which those properties can be determined. In addition, the cooling ages of white dwarf components provide useful limits on the ages of their main sequence companions, independent of other stellar age determination methods. This paper summarizes some of the ways fragile binaries provide useful leverage on these and other problems of interest.

The solar magnetic field that extends through the chromosphere is thought to expand through the transition region into the corona. The strong flux concentrations are located within the boundaries of supergranular convection cells. These boundaries form network lanes, observed in emission lines as bright lanes with varying width throughout the solar atmosphere. These network field concentrations are surrounded by mixed-polarity magnetic field with a scale of the granule diameter, as suggested by observations. We use potential magnetic field extrapolations on synthetic magnetograms to study the magnetic network topology and the effects of background magnetic field on the network expansion through the solar atmosphere. We find that the background magnetic field has a considerable effect on the ratio of network area over field of view. Furthermore we find that the expansion of the network boundaries with height deviate significantly from well-assumed funnel model expansion.

Convection is the main energy transport mechanism in brown dwarf atmospheres. The overshoot of ascending bubbles affects the upper and cooler region where dust formation can occur. In order to understand the observed presence of dust, the formation of grains and their gravitational settling must be balanced by up-mixing of condensible elements via convective overshoot. Otherwise, brown dwarf atmospheres would be completely dust-free (Woitke & Helling 2004).

Based on existing hydrodynamical simulations, we review our present understanding of the formation and evolution of planetary nebulae (PNe) and discuss the relevant processes responsible for the development of the basic (1D) nebular structures.

We study the influence of shock X-ray emission on the structure of non-LTE wind models of O-type stars.

I review the status of massive star formation theories: accretion from collapsing, massive, turbulent cores; competitive accretion; and stellar collisions. I conclude the observational and theoretical evidence favors the first of these models. I then discuss: the initial conditions of star cluster formation as traced by infrared dark clouds; the cluster formation timescale; and comparison of the initial cluster mass function in different galactic environments.

The process of fueling Active Galactic Nuclei (AGN) in galaxies is commonly associated with gas aggregation onto a central supermassive black hole. Up to now a general picture of the AGN fueling is missing: What mechanisms are responsible for the various kinds of AGNs? How to remove angular momentum from the material far away from the gravitational influence of the central black hole? Over the last decade observations have been pointing towards a hierarchy of mechanisms that all combine to transport the gas from the large kpc scales down to the inner pc scales. In addition, fueling mechanisms excited by the galactic environment, e.g. through minor mergers and tidal interactions, have been suggested.

In order to study the gas transport from the outskirts of galaxies to the central AGN, we have embarked on a key project, NUGA (Nuclei of Galaxies): a high spectral and angular resolution CO and HI survey of low luminosity AGN in nearby galaxies (i.e. Seyferts, LINERs and transition objects).

For our detailed HI study, 16 nearby AGN galaxies were observed in their 21 cm line emission of neutral HI gas using the NRAO Very Large Array (VLA) interferometer in its C- and D-array configuration (~20'' angular and ~5.2 km s−1 spectral resolution). The spiral galaxies in our sample range in Hubble type from Sa to Sbc. For all galaxies high quality mm-interferometric CO data as well as optical/NIR imaging data are available.

Here, we present first results on the atomic gas distribution and kinematics in these galaxies: The HI gas properties are analyzed and then compared to the optical properties. Their HI morphology reveals a wide variety: rings, spiral arms, and central concentrated, where ring structures are mostly found in LINER hosts. The integrated surface brightness profiles show some significant differences between the HI gas and stellar light as well as their radial extent. Our analysis of the HI environment yields that 4 galaxies are surrounded by satellites and 8 galaxies have disturbed outer HI disks, probably due to ram pressure stripping and/or minor mergers. Our analysis of the HI kinematics provides rotation curves, dynamical masses and evidence for streaming motions for each galaxy.

The inclusion of recently obtained VLA B-array data will provide ~7″ resolution for more than half of the sample. We will utilize gravity torques based on a definite phase shift between the gravitational potential and the HI gas distribution to determine the gas inflow, and thus the efficiency for feeding the central black hole. Further, the combined CO+HI+NIR/opt data will allow us to develop dynamical models describing the gas flow in galactic disks from the large kpc scales down to the inner pc scales for selected galaxies in our sample.