Related papers: Fluorine Abundances in Galactic AGB Stars
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…
Abundances of fluorine ($^{19}$F), as well as isotopic ratios of $^{16}$O/$^{17}$O, are derived in a sample of luminous young ($\sim$10$^{7}$--10$^{8}$ yrs) red giants in the Galactic center (with galactocentric distances ranging from…
The observational data guiding the theoretical chemical evolutionary models of AGB stars come mainly from the analysis of intrinsic and extrinsic s-process enriched objects. The first are the stars of the M-MS-S-SC-C star sequence which is…
The recent experimental evaluation of the 18F(a,p)21Ne reaction rate, when considering its associated uncertainties, presented significant differences compared to the theoretical Hauser-Feshbach rate. This was most apparent at the low…
Among stars in Galactic globular clusters the carbon abundance tends to decrease with increasing luminosity on the upper red giant branch, particularly within the lowest metallicity clusters. While such a phenomena is not predicted by…
We obtained high-resolution near-IR spectra of 45 AGB stars located in the Galactic bulge. The aim of the project is to determine key elemental abundances in these stars to help constrain the formation history of the bulge. A further aim is…
S-type asymptotic giant branch (AGB) stars are thought to be intermediates in the evolution of oxygen- to carbon-rich AGB stars. The chemical compositions of their circumstellar envelopes are also intermediate, but have not been studied in…
Detailed atmospheric abundances have been calculated for a sample of A-G supergiant stars with IR fluxes and/or high galactic latitudes. HD 172481 and HD 158616 show clear indications of being post-AGB stars that have experienced third…
We numerically investigate abundance properties of the Galactic globular clusters (GCs) by adopting a new ``external pollution'' scenario. In this framework, GCs are assumed to originate in forming low-mass dwarfs embedded in dark matter…
We present fluorine abundances in seven red-giant members of the globular cluster M4 (NGC 6121). These abundances were derived from the HF (1--0) R9 line at 2.3357 microns in high-resolution infrared spectra obtained with the Phoenix…
To better understand the mixing and mass loss experienced by low-mass stars as they ascend the asymptotic giant branch (AGB), I have gathered from the literature the abundances of CNO and s-process elements in post-AGB stars in Galactic…
New SiS multi-transition (sub-)millimetre line observations of a sample of AGB stars with varying photospheric C/O-ratios and mass-loss rates are presented. A combination of low- and high-energy lines are important in constraining the…
Fluorine is massive enough that it is not considered to be a light ($Z\le5$) element, yet compared to its near neighbors, C, N, O, and Ne, it is far underproduced in the course of stellar evolution, making its origin more complex. In fact,…
(Abridged) We demonstrate that the amount of extra mixing required to fit the observed low C/N and 12C/13C ratios in first giant branch (FGB) stars is also sufficient to explain the C and N abundances of Galactic AGB stars. We simulate the…
We present the N, O, F and Na abundance and 12C/13C isotopic ratio measurements or upper limits for a sample of 10 C-rich, metal-poor giant stars, eight enhanced in s-process (CEMP-s) elements and two poor in n-capture elements (CEMP-no).…
It is well known that metal-poor red giant branch (RGB) stars show variations in some elemental abundances, including carbon, due to the internal mixing accompanied by their own in situ CN cycle in the hydrogen burning shell. With our new…
A previously reported literature search suggested that the AGB stars in Galactic globular clusters may be showing different distributions of CN-strong and CN-weak stars as compared to their RGB stars. In most cases the second giant branches…
We extend here a previous investigation on the characteristics of Galactic carbon stars using more accurate EDR3 astrometry measurements. Based on a much larger statistics, we confirm that N- and SC-type carbon stars share a very similar…
Based on our prior accurate determination of fundamental parameters for 36 Galactic A-, F- and G-type supergiants and bright giants (luminosity classes I and II), we undertook a non-LTE analysis of the carbon abundance in their atmospheres.…
W Aql is an asymptotic giant branch (AGB) star with an atmospheric elemental abundance ratio C/O$\approx$0.98 and reported circumstellar molecular abundances intermediate between those of M-type (C/O$<$1) and C-type (C/O$>$1) AGB stars.…