- ID:
- ivo://CDS.VizieR/J/A+A/579/A28
- Title:
- Abundances of 3 CEMP stars
- Short Name:
- J/A+A/579/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of the TOPoS (Turn Off Primordial Stars) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. These stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. We here present our analysis of six CEMP stars. We want to provide the most complete chemical inventory for these six stars in order to constrain the nucleosynthesis processes responsible for the abundance patterns.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/128/343
- Title:
- Abundances of 10 Cepheids
- Short Name:
- J/AJ/128/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a detailed multiphase spectroscopic analysis of 10 classical Cepheids with pulsation periods between 6 and 10 days. For each star, we have derived phased values of effective temperature, surface gravity, microturbulent velocity, and elemental abundances. We show that the elemental abundance results for intermediate-period Cepheids are consistent for all pulsational phases.
- ID:
- ivo://CDS.VizieR/J/A+A/423/867
- Title:
- Abundances of distant luminous infrared galaxies
- Short Name:
- J/A+A/423/867
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One hundred and five 15{mu}m-selected objects in three ISO (Infrared Space Observatory) deep survey fields (CFRS 3h, UDSR and UDSF) are studied on the basis of their high-quality optical spectra with resolution R>1000 from VLT/FORS2. ~92 objects (88%) have secure redshifts, ranging from 0 to 1.16 with a median value of z_med_=0.587.
- ID:
- ivo://CDS.VizieR/J/AJ/132/137
- Title:
- Abundances of extremely metal-poor carbon stars
- Short Name:
- J/AJ/132/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a detailed abundance analysis using high-dispersion spectra from HIRES at Keck for a sample of 16 carbon stars found among candidate extremely metal-poor (EMP) stars from the Hamburg/ESO Survey (HES). We find that the Fe metallicities for the cooler C stars (Teff~5100K) have been underestimated by a factor of 10 by the standard HES tools. The results presented here provided crucial supporting data used recently by Cohen et al. (2005ApJ...633L.109C) to derive the frequency of C stars among EMP stars.
- ID:
- ivo://CDS.VizieR/J/A+A/441/1149
- Title:
- Abundances of 20 F-G disk stars
- Short Name:
- J/A+A/441/1149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Mn, Co and Eu abundances for a sample of 20 disk F and G dwarfs and subgiants with metallicities between -0.8 and +0.3. We investigate the influence of hyperfine structure (HFS) on the derived abundances of Mn and Co by using HFS data from different sources in the literature, as well as calculated HFS from interaction factors A and B.
- ID:
- ivo://CDS.VizieR/J/MNRAS/370/2091
- Title:
- Abundances of HD 134439/40 and HD 211998
- Short Name:
- J/MNRAS/370/2091
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abundances of 18 elements are determined for the common proper-motion pair, HD 134439 and HD 134440, which shows high [Mn/Fe] and low [alpha/Fe] ratios as compared to normal halo stars. Moreover, puzzling abundances are indicated from elements whose origins are normally considered to be from the same nucleosynthesis history. Particularly, we have found that [Mg/Fe] and [Si/Fe] are lower than [Ca/Fe] and [Ti/Fe] by 0.1-0.3dex. When elemental abundances are interpreted in term of their condensation temperatures (T_C_), obvious trends of [X/Fe] versus TC for alpha elements and probably iron-peak elements as well are shown. The hypothesis that these stars have formed from a dusty environment in dwarf spheroidal (dSph) galaxy provides a solution to the puzzling abundance pattern.
- ID:
- ivo://CDS.VizieR/J/A+AS/129/563
- Title:
- Abundances of HR 4487, 14 Hyd and 3 Cen A
- Short Name:
- J/A+AS/129/563
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ussing CASLEO echelle spectrograms, elemental abundances are derived for the sharp-lined non-magnetic CP stars HR 4487, 14 Hya and 3 Cen A. The first two stars are members of the Mercury-Manganese subgroup and have abundances which are similar to other such peculiar stars. The third is a hotter related star. The detection of Mn II lines in its spectrum adds to this relationship.
- ID:
- ivo://CDS.VizieR/J/ApJ/821/37
- Title:
- Abundances of metal-poor star HD 94028
- Short Name:
- J/ApJ/821/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the composition and nucleosynthetic origins of the heavy elements in the metal-poor ([Fe/H]=-1.62+/-0.09) star HD 94028. Previous studies revealed that this star is mildly enhanced in elements produced by the slow neutron-capture process (s process; e.g., [Pb/Fe]=+0.79+/-0.32) and rapid neutron-capture process (r process; e.g., [Eu/Fe]=+0.22+/-0.12), including unusually large molybdenum ([Mo/Fe]= +0.97+/-0.16) and ruthenium ([Ru/Fe]=+0.69+/-0.17) enhancements. However, this star is not enhanced in carbon ([C/Fe]=-0.06+/-0.19). We analyze an archival near-ultraviolet spectrum of HD 94028, collected using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, and other archival optical spectra collected from ground-based telescopes. We report abundances or upper limits derived from 64 species of 56 elements. We compare these observations with s-process yields from low-metallicity AGB evolution and nucleosynthesis models. No combination of s- and r-process patterns can adequately reproduce the observed abundances, including the super-solar [As/Ge] ratio (+0.99+/-0.23) and the enhanced [Mo/Fe] and [Ru/Fe] ratios. We can fit these features when including an additional contribution from the intermediate neutron-capture process (i process), which perhaps operated through the ingestion of H in He-burning convective regions in massive stars, super-AGB stars, or low-mass AGB stars. Currently, only the i process appears capable of consistently producing the super-solar [As/Ge] ratios and ratios among neighboring heavy elements found in HD 94028. Other metal-poor stars also show enhanced [As/Ge] ratios, hinting that operation of the i process may have been common in the early Galaxy.
- ID:
- ivo://CDS.VizieR/J/AN/331/474
- Title:
- Abundances of metal-poor stars
- Short Name:
- J/AN/331/474
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance patterns of the most metal-poor stars in the Galactic halo and small dwarf galaxies provide us with a wealth of information about the early Universe. In particular, these old survivors allow us to study the nature of the first stars and supernovae, the relevant nucleosynthesis processes responsible for the formation and evolution of the elements, early star- and galaxy formation processes, as well as the assembly process of the stellar halo from dwarf galaxies a long time ago. This review presents the current state of the field of "stellar archaeology" -- the diverse use of metal-poor stars to explore the high-redshift Universe and its constituents. In particular, the conditions for early star formation are discussed, how these ultimately led to a chemical evolution, and what the role of the most iron-poor stars is for learning about Population III supernovae yields. Rapid neutron-capture signatures found in metal-poor stars can be used to obtain stellar ages, but also to constrain this complex nucleosynthesis process with observational measurements. Moreover, chemical abundances of extremely metal-poor stars in different types of dwarf galaxies can be used to infer details on the formation scenario of the halo and the role of dwarf galaxies as Galactic building blocks. I conclude with an outlook as to where this field may be heading within the next decade. A table of ~1000 metal-poor stars and their abundances as collected from the literature is provided in electronic format.
- ID:
- ivo://CDS.VizieR/J/ApJ/852/99
- Title:
- Abundances of 3 metal-poor stars in Horologium I
- Short Name:
- J/ApJ/852/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundance measurements of three stars in the ultrafaint dwarf galaxy Horologium I, a Milky Way satellite discovered by the Dark Energy Survey. Using high-resolution spectroscopic observations, we measure the metallicity of the three stars, as well as abundance ratios of several {alpha}-elements, iron-peak elements, and neutron-capture elements. The abundance pattern is relatively consistent among all three stars, which have a low average metallicity of [Fe/H]~-2.6 and are not {alpha}-enhanced ([{alpha}/Fe]~0.0). This result is unexpected when compared to other low-metallicity stars in the Galactic halo and other ultrafaint dwarfs and suggests the possibility of a different mechanism for the enrichment of Hor I compared to other satellites. We discuss possible scenarios that could lead to this observed nucleosynthetic signature, including extended star formation, enrichment by a Population III supernova, and or an association with the Large Magellanic Cloud.
