相关论文: Magnesium isotopic abundance ratios in cool stars

Isotopic abundance ratios 24^Mg:25^Mg:26^Mg are derived for 20 stars from high- resolution spectra of the MgH A-X 0-0 band at 5140AA. With the exception of the weak g-band giant HR 1299, the stars are dwarfs that sample the metallicity…

Magnesium (Mg) isotopic ratios offer valuable insights into stellar nucleosynthesis and Galactic chemical evolution, particularly in distinguishing contributions from supernovae and asymptotic giant branch (AGB) stars. These isotopes are…

Mg isotopic abundance ratios are measured in 20 bright red giants in globular cluster NGC 6752 based on very high-resolution, high signal-to-noise spectra obtained with UVES on the VLT. There is a considerable spread in the ratio…

The abundance of the neutron-rich magnesium isotopes observed in metal-poor stars is explained quantitatively with a chemical evolution model of the local Galaxy that considers - for the first time - the metallicity-dependent contribution…

The abundance of magnesium in the interstellar medium is a powerful probe of star formation processes over cosmological timescales. Magnesium has three stable isotopes, 24Mg, 25Mg, 26Mg, which can be produced both in massive and…

We determine magnesium isotopic abundances of metal poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleossynthesis in the galactic halo and constrain the timescale of its…

We present magnesium abundances derived from high resolution spectra using several Mg I and two high excitation Mg II lines for 19 metal-poor stars with [Fe/H] values between -1.1 and +0.2. The main goal is to search for systematic…

Relative abundances of the five stable isotopes of titanium (^46Ti to ^50Ti) are measured for 11 M dwarfs belonging to the thin disk (four stars), thick disk (three stars), the halo (one star), and either the thick or the thin disk (three…

Using classical model atmospheres and an LTE analysis, Mg isotope ratios 24Mg:25Mg:26Mg are measured in 32 Hyades dwarfs covering 4000K < Teff < 5000K. We find no significant trend in any isotope ratio versus Teff and the mean isotope ratio…

We have determined magnesium isotopic ratios (^{25,26}Mg/Mg) in metal-poor (-2.6 [Fe/H] -1.3) halo dwarfs employing high S/N (90-280) high spectral resolution (R = 10^5) Keck HIRES spectra. Unlike previous claims of an important…

We have determined Mg isotope ratios in halo field dwarfs and giants in the globular cluster M71 based on high S/N high spectral resolution (R = 10$^5$) Keck HIRES spectra. Unlike previous claims of an important contribution from…

We present results of a detailed chemical analysis performed on 23 main-sequence turnoff stars having -3.4<=[Fe/H]<=-2.2, a sample selected to be highly homogeneous in T_eff and log(g). We investigate the efficiency of mixing in the early…

We present Mg isotope ratios in 4 red giants of the globular cluster M 13 and 1 red giant of the globular cluster M 71 based on spectra obtained with HDS on the Subaru Telescope. We confirm earlier results by Shetrone that for M 13, the…

In this work we present and discuss the observations of the Mn abundances for 247 FGK dwarfs, located in the Galactic disc with metallicity -1<Fe/H]<+0.3. The observed stars belong to the substructures of the Galaxy thick and thin discs,…

The many-multiplet method applied to high redshift quasar absorption spectra has indicated a possible time variation of the fine structure constant. Alternatively, a constant value of alpha is consistent with the observational analysis if a…

A critical issue in the asymptotic giant branch (AGB) self-enrichment scenario for the formation of multiple populations in Globular Clusters (GCs) is the inability to reproduce the magnesium isotopic ratios, despite the model in principle…

Strongly Mg-enhanced stars with [Mg/Fe] $>$ 1.0 show peculiar abundance patterns and hence are of great interest for our understanding of stellar formation and chemical evolution of the Galaxy. A systematical search for strongly Mg-enhanced…

We estimate ([M/H], [$\alpha$/M]) for 48 million giants and dwarfs in low-dust extinction regions from the Gaia DR3 XP spectra by using tree-based machine-learning models trained on APOGEE DR17 and metal-poor star sample \revise{from} Li et…

The abundances of iron and oxygen are homogeneously determined in a sample of 523 nearby (d<150 pc) FGK disk and halo stars with metallicities in the range -1.5<[Fe/H]<0.5. The oxygen abundances were inferred from a restricted non-LTE…

[Abridged abstract] We have performed an abundance analysis for 176 F- and G- dwarfs of the Galactic thick disk component. Using accurate radial velocities combined with $Hipparcos$ astrometry, kinematics (U, V, and W) and Galactic orbital…