Abstract. The interstellar medium (ISM) reveals strongly inhomogeneous structures at every scale. These structures do not seem completely random since they obey certain power laws. Larson’s law (1981) σ ∝ R and the plausible assumption of virial equilibrium justify to consider fractals as a possible description of the ISM. In the following we investigate how self-gravitation, differential rotat...

After nearly two decades at least five emission mechanisms can be found in SN 1987A. The ejecta continue to glow as a result of the radioactive decay of long-lived nuclei (mostly 44Ti), but is fading continuously because of the expansion and the reduced opacity. The nearly stationary rings around SN 1987A are still fluorescing from the recombination of matter originally excited by the soft X-ra...

The flux of cosmic ray antiprotons from neutralino annihilations in the galactic halo is computed for a large sample of models in the Minimal Supersymmetric extension of the Standard Model. We also revisit the problem of estimating the background of low-energy cosmic ray induced secondary antiprotons, taking into account their subsequent interactions (and energy loss) and the presence of nuclei...

We calculate the solar-modulated energy spectra of cosmic-ray antiprotons (¯ p's) from two candidate primary sources, i.e., evaporating primordial black holes and the annihilation of neutralino dark matter, as well as for the secondary ¯ p's produced by cosmic-ray interactions with interstellar gas. A large enhancement toward the solar minimum phase emerges in the low-energy flux of ¯ p's from ...

We calculated diffusion timescales for Ca, Mg, Fe in hydrogen atmosphere white dwarfs with temperatures between 5000 and 25000 K. With these timescales we determined accretion rates for a sample of 38 DAZ white dwarfs from the recent studies of Zuckerman et al. (2003) and Koester et al. (2005). Assuming that the accretion rates can be calculated with the Bondi-Hoyle formula for hydrodynamic acc...

Dwarf galaxies pose substantial challenges for cosmological models. In particular, current models predict a dark-matter density that is divergent at the center, which is in sharp contrast with observations that indicate a core of roughly constant density. Energy feedback, from supernova explosions and stellar winds, has been proposed as a major factor shaping the evolution of dwarf galaxies. We...

Recent observations of a large excess of cosmic-ray positrons at high energies have raised a lot of interest in leptonic decay modes of dark matter particles. Nevertheless, dark matter particles in the Milky Way halo could also decay hadronically, producing not only a flux of antiprotons but also a flux of antideuterons. We show that for certain choices of parameters the antideuteron flux from ...

The launch of the RadioAstron space radio telescope provides a unique opportunity to 1 study the extreme high brightness temperature of Active Galactic Nuclei (AGNs) with unprecedented 2 long baselines of up to 28 Earth diameters. A coordinated ground-based flux density monitoring of 3 RadioAstron targets is essential to determine the effect of interstellar scintillation (ISS) on the Space 4 Ve...

The nature of the soft gamma-ray (20-200 keV) Galactic emission has been a matter of debate for a long time. Previous experiments have tried to separate the point source contribution from the real in-terstellar emission, but with a rather poor spatial resolution , they concluded that the interstellar emission could be a large fraction of the total Galactic emission. INTEGRAL, having both high r...

Optical linear polarization measurements are presented for about 30 Vega-like stars. These are then compared with the polarization observed for normal field stars. A significant fraction of the Vega-like stars are found to show polarization much in excess of that expected to be due to interstellar matter along the line of sight to the star. The excess polarization must be intrinsic to the star,...