We have obtained new narrowband CCD images, spatially resolved intermediate- and high-dispersion spectroscopic observations of the Ring Nebula (NGC 6720). These data reveal that the bright main nebula is not a real ring, but a closed shell. A prolate ellipsoidal geometry for this shell is inferred from the observed tilts in the [N II] velocity
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Chemical Abundances and Kinematics of the Ring Nebula and Its HalosGuerrero, M. A. et al.91997
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Chemical abundances and masses of the haloes around the planetary nebulae NGC 6543 and NGC 6826
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
Manchado, A. et al.Advertised on:
91989 -
Chemical Abundances from Inversions of Stellar Spectra: Analysis of Solar-Type Stars with Homogeneous and Static Model Atmospheres
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
Allende Prieto, Carlos et al.Advertised on:
92001 -
Chemical Abundances in the Secondary Star of the Neutron Star Binary Centaurus X-4
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
González Hernández, Jonay I. et al.Advertised on:
92005 -
Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program. Galactic stellar populations and planets
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
Adibekyan, V. Zh. et al.Advertised on:
92012 -
Chemical Abundances of the Secondary Star in the Black Hole X-Ray Binary V404 Cygni
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
González-Hernández, J. I. et al.Advertised on:
92011