- ID:
- ivo://CDS.VizieR/J/A+A/440/321
- Title:
- Chemical abundances in 43 metal-poor stars
- Short Name:
- J/A+A/440/321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni and Ba for 43 metal-poor field stars in the solar neighbourhood, most of them subgiants or turn-off-point stars, with iron abundances [Fe/H] ranging from -0.4 to -3.0. About half of this sample has not been analysed spectroscopically in detail before. Effective temperatures were estimated from uvby photometry, and surface gravities primarily from Hipparcos parallaxes. The analysis is differential relative to the Sun, and carried out with plane-parallel MARCS models. Various sources of error are discussed and found to contribute a total error of about 0.1-0.2dex for most elements, while relative abundances, such as [Ca/Fe], are most probably more accurate. For the oxygen abundances, determined in an NLTE analysis of the 7774{AA} triplet lines, the errors may be somewhat larger.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/161/183
- Title:
- Chemical abundances in 52 M-giant stars
- Short Name:
- J/AJ/161/183
- Date:
- 18 Jan 2022
- Publisher:
- CDS
- Description:
- We measured ^35^Cl abundances in 52-M giants with metallicities in the range -0.5<[Fe/H]<0.12. Abundances and atmospheric parameters were derived using infrared spectra from CSHELL on the NASA Infrared Telescope Facility and from optical echelle spectra. We measured Cl abundances by fitting a H^35^Cl molecular feature at 3.6985{mu}m with synthetic spectra. We also measured the abundances of O, Ca, Ti, and Fe using atomic absorption lines. We find that the [Cl/Fe] ratio for our stars agrees with chemical evolution models of Cl, and the [Cl/Ca] ratio is broadly consistent with the solar ratio over our metallicity range. Both indicate that Cl is primarily made in core-collapse supernovae with some contributions from Type Ia supernovae. We suggest that other potential nucleosynthesis processes, such as the {nu}-process, are not significant producers of Cl. Finally, we also find our Cl abundances are consistent with HII and planetary nebular abundances at a given oxygen abundance, although there is scatter in the data.
- ID:
- ivo://CDS.VizieR/J/ApJ/824/5
- Title:
- Chemical abundances in NGC 5024 (M53)
- Short Name:
- J/ApJ/824/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5m telescope. M53 is of interest because previous studies based on the morphology of the cluster's horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H]=-2.07 with a standard deviation of 0.07dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na-O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.
- ID:
- ivo://CDS.VizieR/J/A+A/360/509
- Title:
- Chemical abundances in 7 red giants
- Short Name:
- J/A+A/360/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical abundances of about fifteen elements from oxygen to europium are measured in seven red giants of the two open clusters NGC 2360 and NGC 2447. The effective temperatures of the giants are determined spectroscopically by taking advantage of their known masses (~2M_{sun}_ in NGC 2360 and ~3M_{sun}_ in NGC 2447) and bolometric magnitudes. The average iron abundances we obtain for the two clusters are [Fe/H]=0.07 for NGC 2360 and [Fe/H]=0.03 for NGC 2447.
- ID:
- ivo://CDS.VizieR/J/AJ/160/181
- Title:
- Chemical abundances in red giants with Magellan
- Short Name:
- J/AJ/160/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution Magellan/MIKE spectroscopy of 42 red giant stars in seven stellar streams confirmed by the Southern Stellar Stream Spectroscopic Survey (S5): ATLAS, Aliqa Uma, Chenab, Elqui, Indus, Jhelum, and Phoenix. Abundances of 30 elements have been derived from over 10000 individual line measurements or upper limits using photometric stellar parameters and a standard LTE analysis. This is currently the most extensive set of element abundances for stars in stellar streams. Three streams (ATLAS, Aliqa Uma, and Phoenix) are disrupted metal-poor globular clusters, although only weak evidence is seen for the light-element anticorrelations commonly observed in globular clusters. Four streams (Chenab, Elqui, Indus, and Jhelum) are disrupted dwarf galaxies, and their stars display abundance signatures that suggest progenitors with stellar masses ranging from 106 to 107M{sun}. Extensive description is provided for the analysis methods, including the derivation of a new method for including the effect of stellar parameter correlations on each star's abundance and uncertainty. This paper includes data gathered with the 6.5m Magellan Telescopes located at Las Campanas Observatory, Chile.
- ID:
- ivo://CDS.VizieR/J/MNRAS/378/1141
- Title:
- Chemical abundances in 31 stars with planet
- Short Name:
- J/MNRAS/378/1141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of detailed spectroscopic abundance analyses for 18 elements in 31 nearby stars with planets (SWPs). The resulting abundances are combined with other similar studies of nearby SWPs and compared to a sample of nearby stars without detected planets. We find some evidence for abundance differences between these two samples for Al, Si and Ti. Some of our results are in conflict with a recent study of SWPs in the SPOCS data base. We encourage continued study of the abundance patterns of SWPs to resolve these discrepancies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/4070
- Title:
- Chemical abundances in the PN Wray16-423
- Short Name:
- J/MNRAS/452/4070
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a detailed analysis of elemental abundances, dust features, and polycyclic aromatic hydrocarbons (PAHs) in the C-rich planetary nebula (PN) Wray16-423 in the Sagittarius dwarf spheroidal galaxy, based on a unique data set taken from the Subaru/HDS, MPG/ESO FEROS, HST/WFPC2, and Spitzer/IRS. We performed the first measurements of Kr, Fe, and recombination O abundance in this PN. The extremely small [Fe/H] implies that most Fe atoms are in the solid phase, considering into account the abundance of [Ar/H]. The Spitzer/IRS spectrum displays broad 16-24 {mu}m and 30 {mu}m features, as well as PAH bands at 6-9 and 10^-14^ {mu}m. The unidentified broad 16-24 {mu}m feature may not be related to iron sulphide (FeS), amorphous silicate, or PAHs. Using the spectral energy distribution model, we derived the luminosity and effective temperature of the central star, and the gas and dust masses. The observed elemental abundances and derived gas mass are in good agreement with asymptotic giant branch nucleosynthesis models for an initial mass of 1.90 M_{sun}_ and a metallicity of Z=0.004. We infer that respectively about 80, 50, and 90 per cent of the Mg, S, and Fe atoms are in the solid phase. We also assessed the maximum possible magnesium sulphide (MgS) and iron-rich sulphide (Fe50S) masses and tested whether these species can produce the band flux of the observed 30 {mu}m feature. Depending on what fraction of the sulphur is in sulphide molecules such as CS, we conclude that MgS and Fe50S could be possible carriers of the 30 {mu}m feature in this PN.
- ID:
- ivo://CDS.VizieR/J/MNRAS/330/75
- Title:
- Chemical abundances in UV-selected galaxies
- Short Name:
- J/MNRAS/330/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the chemical properties of a sample of UV-selected intermediate-redshift (0<=z<=0.4) galaxies in the context of their physical nature and star-formation history. This work represents an extension of our previous studies of the rest-frame UV-luminosity function (Treyer et al., 1998, Cat. <J/MNRAS/300/303>) and the star-formation properties of the same sample (Sullivan et al., 2000, Cat. <J/MNRAS/312/442>). We revisit the optical spectra of these galaxies and perform further emission-line measurements restricting the analysis to those spectra with the full set of emission lines required to derive chemical abundances. Our final sample consists of 68 galaxies with heavy-element abundance ratios and both UV and CCD B-band photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A99
- Title:
- Chemical abundances of 762 FGK stars
- Short Name:
- J/A+A/655/A99
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- To understand the formation and composition of planetary systems, it is essential to have insights into the chemical composition of their host stars. In particular, C/O elemental ratios are useful for constraining the density and bulk composition of terrestrial planets. We study the carbon abundances with a twofold objective. On the one hand, we want to evaluate the behaviour of carbon in the context of Galactic chemical evolution. On the other hand, we focus on the possible dependence of carbon abundances on the presence of planets and on the impact of various factors (such as different oxygen lines) on the determination of C/O elemental ratios. We derived chemical abundances of carbon from two atomic lines for 757 FGK stars in the HARPS-GTO sample, observed with high-resolution (R~115000) and high-quality spectra. The abundances were derived using a standard Local Thermodinamyc Equilibrium analysis with automatically measured Equivalent Widths injected into the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Oxygen abundances, derived using different lines, were taken from previous papers in this series and updated with the new stellar parameters. We find that thick- and thin-disk stars are chemically disjunct for [C/Fe] across the full metallicity range that they have in common. Moreover, the population of high-{alpha} metal-rich stars also presents higher and clearly separated [C/Fe] ratios than thin-disk stars up to [Fe/H]~0.2dex. The [C/O] ratios present a general flat trend as a function of [O/H] but becomes negative at [O/H]>~0dex. This trend is more clear when considering stars of similar metallicity. We find tentative evidence that stars with low-mass planets at lower metallicities have higher [C/Fe] ratios than stars without planets at the same metallicity, in the same way as has previously been found for {alpha} elements. Finally, the elemental C/O ratios for the vast majority of our stars are below 0.8 when using the oxygen line at 6158{AA} however, the forbidden oxygen line at 6300{AA} provides systematically higher C/O values (going above 1.2 in a few cases) which also show a dependence on Teff. Moreover, by using different atmosphere models the C/O ratios can have a non negligible difference for cool stars. Therefore, C/O ratios should be scaled to a common solar reference in order to correctly evaluate its behaviour. We find no significant differences in the distribution of C/O ratios for the different populations of planet hosts, except when comparing the stars without detected planets with the stars hosting Jupiter-type planets. However, we note that this difference might be caused by the different metallicity distributions of both populations. The derivation of homogeneous abundances from high-resolution spectra in samples that are modest in size is of great utility in constraining models of Galactic chemical evolution. The combination of these high-quality data with the long-term study of planetary presence in our sample is crucial for achieving an accurate understanding of the impact of stellar chemical composition on planetary formation mechanisms.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A32
- Title:
- Chemical abundances of 1111 FGK stars
- Short Name:
- J/A+A/545/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a uniform and detailed abundance analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn and V) for a sample of 1111 FGK dwarf stars from the HARPS GTO planet search program. 109 of these stars are known to harbour giant planetary companions and 26 stars are hosting exclusively Neptunians and super-Earths. The main goals of this paper are i) to investigate whether there are any differences between the elemental abundance trends for stars of different stellar populations; ii) to characterise the planet host and non-host samples in term of their [X/H]. The extensive study of this sample, focused on the abundance differences between stars with and without planets will be presented in a parallel paper. The equivalent widths of spectral lines are automatically measured from HARPS spectra with the ARES code. The abundances of the chemical elements are determined using a LTE abundance analysis relative to the Sun, with the 2010 revised version of the spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. To separate the Galactic stellar populations we applied both a purely kinematical approach and a chemical method. We found that the chemically separated (based on the Mg, Si, and Ti abundances) thin and thick discs are also chemically disjunct for Al, Sc, Co and Ca. Some bifurcation might also exist for Na, V, Ni, and Mn, but there is no clear boundary of their [X/Fe] ratios. We confirm that an overabundance in giant-planet host stars is clear for all the studied elements. We also confirm that stars hosting only Neptunian-like planets may be easier to detect around stars with similar metallicities as non-planet hosts, although for some elements (particulary alpha-elements) the lower limit of [X/H] are very abrupt.
