相关论文: Stellar yields and abundances: new directions from…
The determination of heavy element abundances from planetary nebula (PN) spectra provides an exciting opportunity to study the nucleosynthesis occurring in the progenitor asymptotic giant branch (AGB) star. We perform post-processing…
The elemental abundances of ten planetary nebulae, derived with high accuracy including ISO and IUE spectra, are analysed with the aid of synthetic evolutionary models for the TP-AGB phase. Model prescriptions are varied until we achieve…
We review the information that planetary nebulae and their immediate progenitors, the post-AGB objects, can provide to probe the nucleosynthesis and mixing in low and intermediate mass stars. We emphasize new approaches based on high…
The determinations of element abundances in red-giant stars and in particular in AGB stars are reviewed and the resulting abundances are compared with those obtained for planetary nebulae in the Galaxy and in nearby galaxies. The problems,…
Planetary nebulae (PN) represent the evolutionary fate of the asymptotic giant branch (AGB) stellar envelopes, thus are ideally suited to study the chemical impact of AGB stars. Stellar evolution predict elemental enrichment through the AGB…
Type I planetary nebulae (PNe) have high He/H and N/O ratios and are thought to be descendants of stars with initial masses of ~3-8Msun. These characteristics indicate that the progenitor stars experienced proton-capture nucleosynthesis at…
A summary is given of planetary nebulae abundances from ISO measurements. It is shown that these nebulae show abundance gradients (with galactocentric distance), which in the case of neon, argon, sulfur and oxygen (with four exceptions) are…
We previously determined abundances of He, C, N, O, and Ne for a sample of planetary nebulae (PNe) representing a broad range in progenitor mass and metallicity, and we now compare them with theoretical predictions of PNe abundances from a…
A project which aims to understand the abundance patterns of He, C, N, O, Ne, S, and Ar for a small sample of planetary nebulae is described. Abundance ratios of O/H, C/O, and N/O especially show a broad range relative to their solar…
This paper summarizes a project designed to study abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity. We collect abundances of C, N, and O determined for the entire sample and compare…
We explore the elemental abundances in Galactic planetary nebulae (PNe) compared with those of their stellar progenitors (Red Giant Branch and Asymptotic Giant Branch, RGB and AGB, stars), to explore and quantify the expected -- i.e., due…
Neutron(n)-capture elements are produced by s-process nucleosynthesis in low- and intermediate-mass AGB stars, and therefore can be enriched in planetary nebulae (PNe). In the last ten years, n-capture elements have been detected in more…
We compare abundances patterns in the Bulge for elements observed in stars and in planetary nebulae. Some alpha elements, like Mg and Ti, are overabundant respect to Fe, and others are not, like He, O, Si, S, Ar, Ca. The first ones favor a…
AGB stars, the precursors of Planetary Nebulae, exhibit high rates of mass loss and eject material in the form of a slow (10-20 km/s), dusty molecular wind. The general belief that the dust component of AGB circumstellar envelopes have…
Ground- and space-based observations of stellar heavy element abundances are providing a clearer picture of the chemical evolution of the Galaxy. A large number of (r)apid and (s)low neutron capture process elements, including the first…
The abundance of O in planetary nebulae (PNe) has been historically used as a metallicity indicator of the interstellar medium (ISM) where they originated; e.g., it has been widely used to study metallicity gradients in our Galaxy and…
We identify emission lines of post-iron peak elements in very high signal-to-noise spectra of a sample of planetary nebulae. Analysis of lines from ions of Kr and Xe reveals enhancements in most of the PNe, in agreement with the theories of…
We compare the populations of Red Giant stars and Planetary Nebulae in the Galactic Bulge, in the light of recent determinations of their abundances patterns. We find both populations to be compatible. From the planetary nebulae, we find…
Planetary nebulae (PNe) have three main components: a central star (CS), ionised gas and dust in the nebula. Each of them contains critical chemical fingerprints of their evolution, serving as tracers of the evolution, nucleosynthesis and…
We study the chemical abundances of a wide sample of 142 Galactic planetary nebulae (PNe) with good quality observations, for which the abundances have been derived more or less homogeneously, thus allowing a reasonable comparison with…