Related papers: Unusual Isotopic Abundances in a Fully-Convective …
We use state-of-the-art chemical models to track the cosmic evolution of the CNO isotopes in the interstellar medium (ISM) of galaxies, yielding powerful constraints on their stellar initial mass function (IMF). We re-assess the relative…
Isotope ratios have opened a new window into the study of the details of stellar evolution, supernovae, and galactic chemical evolution. We present the evolution of the isotope ratios of elemental abundances (from C to Zn) in the solar…
From high resolution spectra of 61 cool dwarfs and giants, Mg isotopic abundance ratios 24Mg:25Mg:26Mg are derived from spectral synthesis of the MgH A-X lines near 5140A. Our sample spans the range -2.5 < [Fe/H] < 0.1, including the first…
We present results from the volume-complete spectroscopic survey of 0.1-0.3M$_\odot$ M dwarfs within 15pc. This work discusses the active sample without close binary companions, providing a comprehensive picture of these 123 stars with…
By means of chemo-photometric models for galaxies of different morhological types, we have carried out a detailed study of the history of element production by spheroidal and dwarf irregular galaxies. Spheroidal galaxies suffer a strong and…
C and O isotopic ratios are reported for a sample of 46 Mira and SRa-type variable AGB stars. Vibration-rotation 1st and 2nd overtone CO lines in 1.5 to 2.5 $\mu$m spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and…
The J-type carbon (J)-stars constitute 10-15% of the observed carbon stars in both our Galaxy and the Large Magellanic Cloud (LMC). They are characterized by strong 13C absorption bands with low 12C/13C ratios along with other chemical…
ABRIDGED: METHODS: We have conducted a high-resolution spectroscopic study of 714 F and G dwarf and subgiant stars in the Solar neighbourhood. The star sample has been kinematically selected to trace the Galactic thin and thick disks to…
Estimating molecular abundances ratios from the direct measurement of the emission of the molecules towards a variety of interstellar environments is indeed very useful to advance in our understanding of the chemical evolution of the…
We study the evolution, rotation, and surface abundances of O-type dwarfs in the Small Magellanic Cloud. We analyzed the UV and optical spectra of twenty-three objects and derived photospheric and wind properties. The observed binary…
We have analyzed long-slit spectra of 12 dwarf irregular galaxies from the Arecibo Dual Beam Survey (ADBS). These galaxies represent a heterogeneous sample of objects detected by ADBS, but on average are relatively gas-rich,…
Due to a new global analysis method, it is now possible to measure the internal composition of pulsating white dwarf stars, even with relatively simple theoretical models. The precise internal mixture of carbon and oxygen is the largest…
The James Webb Space Telescope's Medium Resolution Spectrometer (MRS), will offer nearly 2 orders of magnitude improvement in sensitivity and >3X improvement in spectral resolution over our previous space-based mid-IR spectrometer, the…
Isotopologue line intensity ratios of circumstellar molecules have been widely used to trace the photospheric elemental isotopic ratios of evolved stars. However, depending on the molecular species and the physical conditions of the…
We present low-resolution spectroscopy of newly-discovered candidate companions to three stars in the Solar Neighbourhood. All three companions are M dwarfs, with spectral types ranging from M4 to M9.5. In two cases, G85-55`B' (M6) and…
Recent observations and theories have presented a strong challenge to the universality of the stellar initial mass function (IMF) in extreme environments. A notable example has been found for starburst conditions, where evidence favours a…
The James Webb Space Telescope (JWST) will open up the possibility of comprehensively measuring the emission spectra of rocky exoplanets orbiting M dwarfs to detect and characterize their atmospheres. In preparation for this opportunity, we…
It has been proposed that the distinct formation and evolution of exoplanets and brown dwarfs may affect the chemical and isotopic content of their atmospheres. Recent work has indeed shown differences in the $^{12}$C/$^{13}$C isotope…
16O/17O and 12C/13C ratios in 23 M giants are determined from high resolution IR spectra observed with the KPNO FTS. The masses of our sample are estimated with the use of the evolutionary tracks by Claret (2004), which could account for…
Oxygen isotope abundances and their ratios are fingerprints of stellar evolution and therefore provide a powerful tool in tracing the enrichment history of galaxies. However, their behavior in low-metallicity dwarf galaxies remains largely…