Related papers: s-Process Abundances in Planetary Nebulae
From newly-obtained high-resolution, high signal-to-noise ratio spectra the abundances of the elements La and Eu have been determined over the stellar metallicity range -3<[Fe/H]<+0.3 in 159 giant and dwarf stars. Lanthanum is predominantly…
Detailed chemical composition studies of stars with enhanced abundances of neutron-capture elements can provide observational constraints for neutron-capture nucleosynthesis studies and clues for understanding their contribution to the…
New abundances of planetary nebulae located towards the bulge of the Galaxy are derived based on observations made at LNA (Brazil). We present accurate abundances of the elements He, N, S, O, Ar, and Ne for 56 PNe located towards the…
A method is presented to derive electron temperatures and densities of planetary nebulae (PNe) simultaneously, using the observed hydrogen recombination spectrum, which includes continuum and line emission. By matching theoretical spectra…
Young pulsars produce relativistic winds which interact with matter ejected during the supernova explosion and the surrounding interstellar gas. Particles are accelerated to very high energies somewhere in the pulsar winds or at the shocks…
We present mid-infrared Spitzer spectra of eleven planetary nebulae in the Galactic Bulge. We derive argon, neon, sulfur, and oxygen abundances for them using mainly infrared line fluxes combined with some optical line fluxes from the…
The most detailed calculations of the p-process call for its development in the O/Ne layers of Type II supernovae. In spite of their overall success in reproducing the solar system content of p-nuclides, they suggest a significant…
We follow the Galactic enrichment of three easily observed light n-capture elements Sr,Y,and Zr.Input stellar yields have been first separated into their respective main and weak s-process,and r-process components.The s-process yields from…
The discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major unresolved problem in nebular astrophysics. We show here that the largest abundance discrepancies are…
We present spectroscopy of nine planetary nebulae (PNe) in the outskirts of M31, all but one obtained with the 10.4m GTC telescope. These sources extend our previous study of the oxygen abundance gradient of M31 to galactocentric radii as…
We present ISO LWS observations of the proto-planetary nebula CRL 618, a star evolving very fast to the planetary nebula stage. In addition to the lines of 12CO, 13CO, HCN and HNC, we report on the detection of H2O and OH emission together…
Ionized nebulae are key to understanding the chemical composition and evolution of the Universe. Among these nebulae, H~{\sc ii} regions and planetary nebulae are particularly important as they provide insights into the present and past…
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…
Spectroscopic observations of 48 emission-line objects of M33 have been obtained with the multi-object, wide field, fibre spectrograph AF2/WYFFOS at the 4.2m WHT telescope (La Palma, Spain). Line intensities and logarithmic extinction,…
Diffuse X-ray emission has been detected in a small number of planetary nebulae (PNe), indicating the existence of shocked fast stellar winds and providing support for the interacting-stellar-winds formation scenario of PNe. However, the…
We derive the stellar and circumstellar parameters of the Galactic compact planetary nebula Hen 2-90 with two models: the classical constant density nebula model where the emission (especially of the forbiden lines) is formed in a sphere or…
We present new abundance determinations of neutron-capture elements Ge, Zr, Os, Ir, and Pt in a sample of 11 metal-poor (-3.1 <= [Fe/H] <= -1.6) Galactic halo giant stars, based on Hubble Space Telescope UV and Keck I optical…
During the evolution on the AGB, S-type stars are the first objects to experience s-process nucleosynthesis and third dredge-ups, and therefore to exhibit sprocess signatures in their atmospheres. Their significant mass loss rates (10^-7 to…
Abundances of heavier elements (barium and beyond) in many neutron-capture-element-rich halo stars accurately replicate the solar system r-process pattern. However, abundances of lighter neutron-capture elements in these stars are not…
Planetary nebulae (PNe) and their central stars (CSs) are ideal tools to test evolutionary theory: photospheric properties of their exciting stars give stringent constraints for theoretical predictions of stellar evolution. The nebular…