Pulsating stars of different types are in different evolutionary phases, thus allowing one to trace stellar components of different age in the host systems. The light variation caused by the cyclic expansion/contraction of the surface layers makes a pulsating star much easier to identify than constant stars in the same evolutionary phase. Pulsating stars thus offer a powerful tool to disentangle the various stellar generations in systems where stars of different age and metal abundance populate the same regions of the colour-magnitude diagram. An overview is presented of how pulsating stars can be used as tools to study the stellar populations, and the structure and formation process in Local Group galaxies.

By now, observations of exoplanets have found more than 50 binary star systems hosting 71 planets. We expect these numbers to increase as more than 70% of the main sequence stars in the solar neighborhood are members of binary or multiple systems. The planetary motion in such systems depends strongly on both the parameters of the stellar system (stellar separation and eccentricity) and the architecture of the planetary system (number of planets and their orbital behaviour). In case a terrestrial planet moves in the so-called habitable zone (HZ) of its host star, the habitability of this planet depends on many parameters. A crucial factor is certainly the amount of water. We investigate in this work the transport of water from beyond the snow-line to the HZ in a binary star system and compare it to a single star system.

The analysis of radial velocities in the spectra of HD 151932 and HD 152233, performed for the optical lines of interstellar CH and CH+ molecules on one hand, and for the diffuse bands 4964 and 6196 Å on the other hand, suggests that the carrier of the former DIB is spatially related to CH, while the carrier of the latter - to CH+. A further analysis, based on the sample of 106 reddened OB stars, partly confirms this suggestion, showing that the CH column density correlates indeed much better with the equivalent width of the 4964 DIB than with that of the 6196 DIB.

We report our present efforts for introducing magnetic fields in the ATON stellar evolution code code, which now evolved to truly modifying the stellar structure equations so that they can incorporate the effects of an imposed, large-scale magnetic field. Preliminary results of such an approach, as applied to low-mass stellar models, are presented and discussed.

The final 800 sq. deg of sky covered by FIRST was observed with the new, improved JVLA. The data were split between two bandpasses at 1335 and 1730 MHz and included all four Stokes parameters, thus allowing both spectral and polarimetric results. The lower frequency bandpass data were considered part of FIRST and are available through the FIRST website (http://sundog.stsci.edu/). Here we present the higher frequency bandpass data as pertain to AGN. Foremost, we present spectral index results for the 5000 quasars with spectroscopic redshifts and the 50,000 quasars with photometric redshifts that fall in the survey area. The spectral indices are analyzed as a function of redshift and optical properties both for quasars detected above the 1 mJy limit and, via image stacking, for quasars at flux densities down to 10 mJy.

Dust plays an important role in our understanding of the near and distant Universe. The enormous amounts (≳108M⊙) of dust observed at high redshifts have forced us to revisit the commonly-invoked sites of dust production. Although core-collapse supernovae are the prime candidates for cosmic dust production, their actual contribution to the dust budget has been the subject of much debate in recent years. Here, I will discuss results from several vigorous observational campaigns aimed at quantifying the amount of dust produced by core-collapse supernovae. Although sample sizes are still modest, I will attempt to put the role of supernovae as dust producers into perspective.

Because of its large angular extent, the central molecular zone (CMZ) has to date only been mapped in the mm with single dish telescopes, with resolution about 30″ (1.4 pc). We present the first interferometric maps of a 90 × 50 pc region of the CMZ, with spatial resolution of ∼10″ (0.4 pc). We mapped ∼0.25 square degrees of the CMZ with CARMA in 3mm continuum and the spectral lines SiO J = (2 − 1), HCO+J = (1 − 0), HCN J = (1 − 0), N2H+J = (1 − 0), and CS J = (2 − 1), covering roughly VLSR = −200 to 200 km s−1 with spectral resolution ΔV ∼ 2.5 km s−1. To recover the large scale structure resolved out by the interferometer, the continuum-subtracted spectral line images were combined with the Mopra 22-m telescope survey.

Using the IRAM 30 m telescope, we perform a molecular line survey of the 3 and 2 mm wavelength ranges towards 5 selected positions in the Galactic center region, sampling shocked regions, ultraviolet (UV) and X-ray pervaded regions, and positions with rich organic chemistry. These surveys have the potential to be used as chemical templates for different types of activity, such as photodissociated regions (PDRs), shocks and X-ray dominated regions (XDRs). Complementary, molecular surveys done towards extragalactic nuclei, that are also dominated by these physical activities, were carried by our group.

Passages of comet-like bodies through the atmosphere/chromosphere of massive stars at velocities more than 600 km/s will be accompanied, due to aerodynamic effects as crushing and flattening, by impulse generation of hot plasma within a relatively very thin layer near the stellar surface/photosphere as well as “blast” shock wave, i.e., impact-generated photospheric stellar/solar flares. Observational manifestations of such high-temperature phenomena will be eruption of the explosive layer's hot plasma, on materials of the star and “exploding” comet nuclei, into the circumstellar environment and variable anomalies in chemical abundances of metal atoms/ions like Fe, Si etc. Interferometric and spectroscopic observations/monitoring of young massive stars with dense protoplanetary discs are of interest for massive stars physics/evolution, including identification of mechanisms for massive stars variability.

Very Long Baseline Interferometry (VLBI) provides the highest angular resolution achievable in astronomy, reaching sub-milliarcsecond scales. For radio loud AGNs, this offers the unique opportunity to directly image and monitor the fine details of the jet structure, approaching the event horizon in the nearest and most supermassive black holes, like in M87. After a quick review of various VLBI facilities, we present results from recent VLBI monitoring projects on two remarkable radio and high energy sources: the radio galaxy M87 and the BL Lac object Mrk421. For the latter, we present a detailed analysis of the jet structure in total intensity and polarization through the whole 2011, during which a multi-wavelength campaign took place. We reveal flux density variability but no significant changes in the jet structure. In M87, we detect and follow the evolution of the core and of the jet feature HST-1; we reveal superluminal motion of components within HST-1, with a possible connection between ejection of new such components and the occurrence of very high energy flares. Estimates on the physical parameters for both sources are given (Doppler factor, viewing angle, magnetic field, etc.).

The Sun is the archetype of magnetic star and its proximity coupled with very high accuracy observations has helped us understanding how solar-like stars (e.g with a convective envelope) redistribute angular momentum and generate a cyclic magnetic field. However most solar models have been so fine tuned that when they are applied to other solar-like stars the agreement with observations is not good enough. I will thus discuss, based on theoretical considerations and multi-D MHD stellar models, what can be considered as robust properties of solar-like star dynamics and magnetism and what is still speculative. I will derive scaling laws for differential rotation and magnetic energy as a function of stellar parameters, discuss recent results of stellar dynamo models and define the new concept of spot-dynamo, e.g. global dynamo that develops self-consistent magnetic buoyant structures that emerge at the surface.

Pulsating pre-main-sequence (PMS) stars afford the earliest opportunity in the lifetime of a star to which the concepts of asteroseismology can be applied. PMS stars should be structurally simpler than their evolved counterparts, thus (hopefully!) making any asteroseismic analysis relatively easier. Unfortunately, this isn't necessarily the case. The majority of these stars (around 80) are δ Scuti pulsators, with a couple of γ Doradus, γ Doradus – δ Scuti hybrids, and slowly pulsating B stars thrown into the mix. The majority of these stars have only been discovered within the last ten years, with the community still uncovering the richness of phenomena associated with these stars, many of which defy traditional asteroseismic analysis.

A systematic asteroseismic analysis of all of the δ Scuti PMS stars was performed in order to get a better handle on the properties of these stars as a group. Some strange results have been found, including one star pulsating up to the theoretical acoustic cut-off frequency of the star, and a number of stars in which the most basic asteroseismic analysis suggests problems with the stars' positions in the Hertzsprung-Russell diagram. From this we get an idea of the\break constraints — or lack thereof — that these results can put on PMS stellar evolution.

Bulges are commonly believed to form in the dynamical violence of galaxy collisions and mergers. We model the stellar kinematics of the Bulge Radial Velocity Assay (BRAVA) and find no sign that the Milky Way contains a classical bulge formed by scrambling pre-existing disks of stars in major mergers. Rather, the bulge appears to be a bar seen somewhat end-on, as hinted from its asymmetric boxy shape. We construct a simple but realistic N-body model of the Galaxy that self-consistently develops a bar. The bar immediately buckles and thickens in the vertical direction. As seen from the Sun, the result resembles the boxy bulge of our Galaxy. We use the new kinematic constraints to show that the classical bulge contribution cannot be very significant. The model fits the BRAVA stellar kinematic data covering the whole bulge strikingly well with no need for a merger-made classical bulge. Our model contains an intriguing vertical X-shaped structure that resembles the similar structure reported recently in the Galactic bulge. The existence of the vertical X-shaped structure also suggests that the formation of the Milky Way bulge is shaped mainly by internal disk dynamical instabilities.

Perturbation theory in the three body problem has greatly advanced our ability to understand and model a variety of systems ranging from artificial satellites to stars and from extrasolar planets to asteroid-Jupiter interactions. In a series of papers, we developed an analytical technique for estimating the orbital eccentricity of the inner binary in hierarchical triple systems. The method combined the secular theory with calculations of short period terms. The derivation of the short term component was based on an expansion of the rate of change of the Runge-Lenz vector by using first order perturbation theory, while canonical perturbation theory was used to investigate the secular evolution of the system. In the present work we extend the calculation to the orbit of the outer binary. At the same time, we provide an improved version for some previous results. A post-Newtonian correction is included in our model. Our analytical estimates are compared with numerical and analytical results on the subject and applications to stellar triples and extrasolar planets are discussed.

We study the formation of molecules and dust clusters in the ejecta of solar metallicity, Type II-P supernovae using a chemical kinetic approach and follow the evolution of molecules and small dust cluster masses from day 100 to day 1500 after explosion. We predict that large masses of molecules including CO, SiO, SiS, O2, and SO form in the ejecta. We show that the non-equilibrium chemistry results in a gradual build up of the dust mass from small (~10−5M⊙) to large values (~5×10−2M⊙) over a five-year period after explosion. This result provides a natural explanation to the discrepancy between the small dust masses detected at infrared wavelengths some 500 days post-explosion and the larger amounts of dust recently detected with the Herschel telescope in supernova remnants.

We present a preliminary analysis of a set of optical (3800-8800 Å) high resolution (R = 80,000) spectra for 69 diffuse interstellar band targets. We carried out a sensitive search for interstellar features in the wavelength range 8470-8740 Å that will be covered by the upcoming GAIA mission. We also investigate how the λ8620Å DIB strength varies as a function of other interstellar parameters (other DIBs, E(B-V) and atomic and molecular column densities).

Three-dimensional kinematic reconstructions of optically emitting ejecta in the young Galactic supernova remnant Cassiopeia A (Cas A) are discussed. The reconstructions encompass the remnant's faint outlying ejecta knots, including the exceptionally high-velocity NE and SW streams of debris often referred to as ‘jets’. The bulk of Cas A's ejecta are arranged in several circular rings with diameters between approximately 30″ (0.5 pc) and 2′ (2 pc). We suggest that similar large-scale ejecta rings may be a common phenomenon of young core-collapse remnants and may explain lumpy emission line profile substructure sometimes observed in spectra of extragalactic core-collapse supernovae years after explosion. A likely origin for these large ejecta rings is post-explosion input of energy from plumes of radioactive 56Ni-rich ejecta that rise, expand, and compress non-radioactive material to form bubble-like structures.

We have detected 62 compact likely extragalactic sources in the Galactic center (GC) region at 0.154 and 0.255 GHz with the Giant Metrewave Radio Telescope (GMRT). Their scattering sizes go down linearly with angular distance from the GC up to about 1°. These are more than 10 times lower than the proposed Hyperstrong scattering model within 0.5° from the GC. We also detect 7 out of 10 EG sources expected in the region from existing catalogs. Ionized interfaces of dense molecular clouds to the ambient medium are likely responsible for strong scattering. However, dense GC clouds traced by CS J = (1 − 0) emission are found to have a narrow distribution of ∼0.2° across the Galactic plane. Lack of strong scattering towards EG sources within ∼ 0.5° from GC with |b| ≳ 0.2° could explain our results.

The Kepler mission has recently discovered a number of exoplanetary systems, such as Kepler 11, in which ensembles of several planets are found in very closely packed orbits. These systems present a challenge for traditional formation and migration scenarios. We present a dynamical study of the evolution of these systems using an N-body approach, incorporating both smooth and stochastic migration forces and a variety of initial conditions, in order to assess the feasibility of assembling such systems via traditional, disc-driven migration.

The projection factor used in the Baade-Wesselink method of determining the distance of Cepheids makes the link between stellar physics and the cosmological distance scale. A coherent picture of this physical quantity is now provided based on several approaches. We present the latest news on the expected projection factor for different kinds of pulsating stars in the Hertzsprung-Russell diagram.