We study spectroscopically determined iron abundances of 642 solar-type stars to search for the signature of accreted iron-rich material. We find that the metallicity [Fe/H] of a subset of 466 main sequence stars, when plotted as a function of stellar mass, mimics the pattern seen in lithium abundances in open clusters. Using Monte Carlo models we find that, on average, these stars have accrete...

We consider the possibility that a mass of ∼ 10 − 10M⊙ flows back from the dense shell of planetary nebulae and is accreted by the central star during the planetary nebula phase. This backflowing mass is expected to have a significant specific angular momentum even in (rare) spherical planetary nebulae, such that a transient accretion disk might be formed. This mass might influence the occurren...

Early-type dwarfs are the most common galaxy in the local universe, yet their origin and evolution remain a mystery. Various cosmological scenarios predict that dwarf-like galaxies in dense areas are the first to form and hence should be the oldest stellar systems in clusters. By using radial velocities of early-type dwarfs in the Virgo cluster we demonstrate that these galaxies are not an old ...

We show that long–period dwarf novae offer a promising route for making Type Ia supernovae. For typical dwarf nova duty cycles d ∼ 0.1 − 0.01, mass is accreted by the white dwarf mainly during dwarf nova outbursts at rates allowing steady nuclear burning of most of the accreted matter. Mass gains up to ∼ 0.4M⊙ are possible in this way. Although these are too small to allow a 0.7M⊙ WD to reach t...

We suggest that the growth of the central black hole in active galactic nuclei (AGN) due to the matter accreted over the AGN lifetime causes an evolution of the luminosity and spectrum. In a previous paper we have shown that the effective temperature of the UV continuum spectrum and the emission-lineequivalent width are anti-correlated with the black-hole mass. Here we estimate the change in th...

We look at the spreading of localized temperature perturbations in the accreted fuel layer of a non-rotating neutron star. The pressure at the base of the accreted fuel layer is large and the material is only partially degenerate. Any temperature perturbations and resulting pressure gradients will lead to enormous accelerations (both laterally and vertically) of the material in the fuel layer. ...