Rapidly rotating solar type stars display varying amounts ofchromospheric emission in their Balmer lines. The profiles of theselines often display rapid variability. Since the mid-1980s,high-cadence echelle spectroscopy of numerous such stars has revealedthat some of the variability is caused by concentrations of neutralhydrogen, trapped in the stellar coronal magnetic field at distancesup to a few stellar radii from the rotation axis. In this paper wereview the observations and the tomographic techniques that can beapplied to mapping these "slingshot prominence" systems. We discussthe possible mechanisms for formation and mechanical support of thesecondensations, in the light of recent efforts to map 3-dimensionalstellar coronal magnetic fields and X-ray emission measuredistributions, with the help of Zeeman-Doppler imaging.

Irradiation by cosmic ions plays a relevant role in the “space weathering” of solid materials in the airless bodies (rocky and/or icy objects) in the Solar System. Here, I discuss about some of the effects that have been studied in “simulation” experiments with a view to their astrophysical relevance. In particular I review some experimental results obtained so far after irradiation of relevant materials, namely: sputtering, ion implantation, and chemical synthesis of molecular species different from the original ones. All of those effects are accomplished by changes in the optical properties of irradiated layers and then of the color of the surfaces of the airless bodies. Some specific examples of the application of the experimental results to the physics and chemistry of planetary surfaces are discussed as well.

Modeling of molecular emission from interstellar clouds requires the calculation of rate coefficients for excitation by collision with the most abundant species. Based on new highly correlated potential energy surfaces, rotational excitation of C2H and C2H− radicals in collision with He are investigated. C2H fine and hyperfine structure is taken into account. As already found for other systems, rate coefficients for the C2H− ion are larger by a factor up to 3 compared to the neutral species.

We discuss the selection of blue horizontal branch stars (BHBs) using preliminary Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) color data and outline techniques for structure detection using those data. We first outline the adaptation of an old color selection for for BHBs using Sloan Digital Sky Survey (SDSS) data to the Pan-STARRS filter set. We next outline a rudimentary search algorithm designed to autonomously detect substructure in the Galactic halo. Finally we discuss preliminary results and comment on future refinements to the process.

We are using a sample of more than 50 standard very late-type stars, taken from Isaac Newton Telescope at R  ~ 9000 in the 8100–9100 Å range, in order to develop criteria for spectral and luminosity classification of very late-type stars in the Gaia region. In this article, we brief in a few pages the main challenges on this issue, as well as the literature about it, and we present some preliminary results.

We investigate the influence of radiative transport on the growth of the magnetorotational instability (MRI) in accretion discs. A general dispersion relation describing the growth of small disturbances on a homogeneous background shear flow is provided. It includes compressibility and radiative effects in the flux-limited diffusion approximation. All the effects of radiation transport can be subsumed into one single parameter, an effective speed of sound. Radiative diffusion does not affect the region where the MRI operates, but it alters the growth rates of the MRI either by increasing or decreasing them. We report about corresponding numerical simulations, which are also used for a first investigation of the non-linear stage of the MRI in gas-pressure dominated accretion discs with radiation transport included.

Spectral surveys provide the only way to determine the full molecular inventory of a source and hence to build a comprehensive view of the state of the molecular gas and its role in the star formation process. Systematic studies have opened the possibility of using chemistry as a diagnostic tool for star burst and AGN activities in the highly obscured galactic nuclear regions.

Irradiation is one of the main processes which influences the evolution of dust in astrophysical environments. This article reviews the basics of particle-matter interactions and gives an introduction to the induced modifications including phase transformation, sputtering, implantation, charging effects and transmutation. We also discuss the role of the nature of the incident particle (energetic photons, electrons and ions) as a function of its energy. Finally, we briefly review the main results obtained by irradiation studies on ices, carbonaceous matter and silicates.

VIHI: the Visible and Infrared Hyperspectral Imager is one of the three channels of the Simbio-Sys instrument for the BepiColombo mission to Mercury. Its scientific objective is to study the hermean surfaces composition by sensing the photon flux reflected off the planet. VIHI works in the range of 400 to 2000 nm with a spectral resolution around a few hundreds. The particularity of this channel is the use of a single detector matrix (264 × 264) for both visible and infrared wavelengths. Getting the visible part of the detector responsivity is achieved by thinning an infrared HgCdTe matrix because visible light is completely absorbed inside the substrate. The thinning process is well controlled since a long time and was used to increase number of thermal cycle of the hybrid devices. Recently, this process is able to remove completely the substrate and, thus, open the detector to the visible range. The detector is a custom design made by Raytheon Vision System in Goleta (USA). In this paper, we will describe the expected performances of the detector which is designed to work in the very harsh radiation environment of Mercury.

Dust grains are an important component of star forming regions and are therefore a powerful tracer of the location and mass of prestellar cores. However, the properties of dust grains in such dense regions are poorly constrained, causing difficulties in the modeling of the physical properties of dense cores. One of the fundamental properties of dust grains is their size distribution, which is relatively well-known in the diffuse ISM but not very well constrained in dense regions. Indirect evidence is consistent with the presence of large grains; however, to date, interpreting submm emission measurements or absorption in the near-infrared (NIR)/mid-infrared (MIR) domains is difficult due to the ambiguity between density (and temperature if in emission) variations and grain properties. Recently, we have discovered emission at 3.6 and 4.5 μm towards the densest parts of L183. We have named this effect coreshine, by analogy with the cloudshine, seen at the surface of dark clouds in the near-infrared. This 3.6 and 4.5 μm emission can only be explained by the strong scattering of background interstellar radiation due to micron-size grains and show that the average grain size increase needs to be proportional to the cloud core density gradient to reproduce the observations. We show that the scattering effect is very sensitive to the grain size distribution; therefore these observations will provide a new tool with which to study grain properties. In a subsequent search through about a hundred of dense low mass core regions in the Spitzer Heritage Archive, we find that the effect is present in  ~50% of the sources, including prestellar cores, Class 0 and I sources with or without outflow, showing that the coreshine effect should rapidly become a general observational method to investigate dark cloud and grain properties.

We analyze a sample of Swift X-ray and optical GRB afterglows which werechosen so as to reduce selection effects against the weakest events. We tentativelyidentify important differences in GRBs that show a fast decay with respect to the averageGRB, in particular a tendency for the more energetic bursts to have a steeper afterglowdecline. An explanation to this finding could be bursts in a wind environment are onaverage more energetic than bursts occurring in a constant density medium.

The results of investigation of 43 peaked R-band light curves of optical transients ofgamma-ray bursts with known redshifts are presented. The parameters of optical transientswere calculated in the comoving frame, and then a search for pair correlations betweenthem was conducted. As a result of the statistical analysis, a strong correlation betweenthe peak luminosity and redshift was found for pure afterglows and the events withresidual gamma activity, which can’t be explained as an effect of observational selection.It suggests the cosmological evolution of the parameters of the local interstellar mediumaround the sources of gamma-ray burst. In the models of forward and reverse shock waves, arelation between the density of interstellar medium and redshift was built for gamma-rayburst afterglows. It was shown that for GRB host galaxies the star formation rateincreases with redshift.

This paper analyses cosmological observations within inhomogeneous and exact solutions of the Einstein equations. In some way the analyses presented here can be freed from assumptions such as small amplitude of the density contrast.The supernova observations are analysed using the Lemaître–Tolman model and the CMB observations are analysed using the quasispherical Szekeres model.The results show that it is possible to fit the supernova datawithout the cosmological constant. However ifinhomogeneities of sizes and amplitudes as observed in the local Universeare considered, their impact on cosmological observations is small.

The three instruments on the Herschel Space Observatory, HIFI, SPIRE, and PACS, cover together over a decade in frequency, from 450 GHz to 5000 GHz, with spectral resolutions δν/ν between 0.3 and 10-6. The equivalent temperature range, defined by T = hν/k is 21 K ≤ Teq ≤ 240 K, and thus for dust emission, Herschel will cover the peak of the Planck function in many sources associated with both quiescent and star-forming molecular clouds, both in the Milky Way and other galaxies. The temperature equivalence of the Herschel frequency range also means that essentially all portions of giant molecular clouds will be well probed by the many spectral lines in the Herschel wavelength range of 0.67 mm to 60 µm. My focus in this paper is on gas phase spectral lines of molecules, atoms, and ions, which will be well resolved with the heterodyne receivers on HIFI, but typically not resolved in Galactic sources with the other two instruments. Kinematic interpretation of spectral lines with HIFI is of great interest, along with determination of temperature, density, and column density. I briefly summarize in this review the most important species for Herschel observations, and discuss how one can derive important astronomical quantities from data obtained with the Herschel Space Observatory. Along with describing techniques for analyzing data from the Herschel instruments, I will cover briefly what supplementary ground–based observations are necessary to extract the most from the valuable observing time of the space–based facility.

We present two newly discovered cE galaxies with tidal tails, the “smoking gun” of the stripping scenario for cE formation.

The Very Large Telescope (VLT) Observatory on Cerro Paranal (2635 m) in Northern Chile is approaching completion. After the four 8-m Unit Telescopes (UT) individually saw first light in the last years, two of them were combined for the first time on October 30, 2001 to form a stellar interferometer, the VLT Interferometer. The remaining two UTs will be integrated into the interferometric array later this year, so that any two UTs can be used for interferometry. In this article, we will describe the subsystems of the VLTI and the planning for the following years.

The origin of solar energetic particle (SEP) events is an issue for the understanding of particle acceleration and transport in astrophysics, as well as for space weather. We outline some recent studies addressing from the observational viewpoint the relationship between interacting and escaping particles, conditions for particle escape from the Sun, and the interplanetary magnetic field configurations where the particles propagate.

The analysis of a sample of 30 isolated spiral galaxies with andwithout an Active Galactic Nucleus (AGN) results in active and control galaxies having similarbulge and disk properties. Secondary bars also seem to beindistinguishable. Circumnuclear kinematics are also analyzed todisentangle what kind of mechanisms are taking place in thecircumnuclear regions. From long slit spectra of a subsample ofisolated active and non-active spiral galaxies in the Hαemission line region, the shape and properties of the rotation curvesare obtained together with the line ratios used to estimate themetallicity of all the detected HII regions. Kinematics andmetallicities are also studied in comparison with the propertiesdetermined for a family of 111 spiral galaxies with a welldetermined environmental status, ranging from isolation to close, though not disruptive, interaction with satellites or companions. Thestellar kinematics are also studied in some cases, with as mainresult the detection of a stellar velocity dispersion drop in thecenters of four Seyfert galaxies. Together with previous findings, ourresults from the comparison between active and non-active isolatedgalaxies point to AGNs being an episode in the life of galaxies,provided that the fuel is available and the accumulation mechanismsare at work.

With targeted imaging of groups in the local volume, the regions of collapse around bright galaxies can be clearly identified by the distribution of dwarfs and luminosity functions can be established to very faint levels. In the case of the M 81 Group there is completion to MR ~ −9. In all well studied cases, the faint end slopes are in the range − 1.35 < α < −1.2, much flatter than the slope for the bottom end of the halo mass spectrum anticipated by ΛCDM hierarchical clustering theory. Small but significant variations are found with environment. Interestingly, the populations of dwarf galaxies are roughly constant per unit halo mass. With the numbers of dwarfs as an anchor point, evolved environments (dominated by early morphological types) have relatively fewer intermediate luminosity systems and at least one relatively more important galaxy at the core. The variations with environment are consistent with a scenario of galaxy merging. However it is questionable if the universal dearth of visible dwarf systems is a consequence of an astrophysical process like reionization.