Spatial resolved low resolution spectroscopy of the haloes around the planetary nebulae NGC 6543 and NGC 6826 were conducted. The results imply that the radiation is thermal and not due to dust reflection. From those data chemical abundances and masses were calculated. Chemical abundances decrease in the haloes, while masses increase up to ten

Spectra of late-type stars are usually analyzed with static model atmospheres in local thermodynamic equilibrium (LTE) and a homogeneous plane-parallel or spherically symmetric geometry. The energy balance requires particular attention, as two elements that are particularly difficult to model play an important role: line blanketing and convection

Using a high-resolution spectrum of the secondary star in the neutron star binary Cen X-4, we have derived the stellar parameters and veiling caused by the accretion disk in a consistent way. We have used a χ2 minimization procedure to explore a grid of 1,500,000 LTE synthetic spectra computed for a plausible range of both stellar and veiling

Context. We performed a uniform and detailed abundance analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn, and V) for a sample of 1111 FGK dwarf stars from the HARPS GTO planet search program. Of these stars, 109 are known to harbor giant planetary companions and 26 stars are exclusively hosting Neptunians and super

To understand the formation and composition of planetary systems it is important to study their host stars composition since both are formed in the same stellar nebula. In this work, we analyze the behaviour of chemical abundances of Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu in the large and homogeneous HARPS-GTO planet search sample (R ˜ 115000). This

We present a chemical abundance analysis of the secondary star in the black hole binary V404 Cygni, using Keck I/High Resolution Spectrometer. We adopt a χ2-minimization procedure to derive the stellar parameters, taking into account any possible veiling from the accretion disk. With these parameters we determine the atmospheric abundances of O, Na