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341. Abundances of six RGB stars in M22
ID:
ivo://CDS.VizieR/J/ApJ/742/37
Title:
Abundances of six RGB stars in M22
Short Name:
J/ApJ/742/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an empirical s-process abundance distribution derived with explicit knowledge of the r-process component in the low-metallicity globular cluster M22. We have obtained high-resolution, high signal-to-noise spectra for six red giants in M22 using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory. In each star we derive abundances for 44 species of 40 elements, including 24 elements heavier than zinc (Z=30) produced by neutron-capture reactions. Previous studies determined that three of these stars (the "r+s group") have an enhancement of s-process material relative to the other three stars (the "r-only group"). We confirm that the r+s group is moderately enriched in Pb relative to the r-only group. Both groups of stars were born with the same amount of r-process material, but s-process material was also present in the gas from which the r+s group formed. The s-process abundances are inconsistent with predictions for asymptotic giant branch (AGB) stars with M<=3M_{sun}_ and suggest an origin in more massive AGB stars capable of activating the ^22^Ne({alpha},n)^25^Mg reaction. We calculate the s-process "residual" by subtracting the r-process pattern in the r-only group from the abundances in the r+s group. In contrast to previous r- and s-process decompositions, this approach makes no assumptions about the r- and s-process distributions in the solar system and provides a unique opportunity to explore s-process yields in a metal-poor environment.
342. Abundances of solar analogs with planets
ID:
ivo://CDS.VizieR/J/ApJ/720/1592
Title:
Abundances of solar analogs with planets
Short Name:
J/ApJ/720/1592
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a fully differential chemical abundance analysis using very high resolution ({lambda}/{delta}{lambda}>~85000) and very high signal-to-noise (S/N~800 on average) HARPS and UVES spectra of 7 solar twins and 95 solar analogs, of which 24 are planet hosts and 71 are stars without detected planets. The whole sample of solar analogs provides very accurate Galactic chemical evolution trends in the metallicity range -0.3<[Fe/H]<0.5. Solar twins with and without planets show similar mean abundance ratios. We have also analyzed a sub-sample of 28 solar analogs, 14 planet hosts, and 14 stars without known planets, with spectra at S/N~850 on average, in the metallicity range 0.14<[Fe/H]<0.36, and find the same abundance pattern for both samples of stars with and without planets. This result does not depend on either the planet mass, from 7 Earth masses to 17.4 Jupiter masses, or the orbital period of the planets, from 3 to 4300 days. In addition, we have derived the slope of the abundance ratios as a function of the condensation temperature for each star and again find similar distributions of the slopes for both stars with and without planets. In particular, the peaks of these two distributions are placed at a similar value but with the opposite sign to that expected from a possible signature of terrestrial planets. In particular, two of the planetary systems in this sample, each of them containing a super-Earth-like planet, show slope values very close to these peaks, which may suggest that these abundance patterns are not related to the presence of terrestrial planets.
343. Abundances of 15 solar analogues
ID:
ivo://CDS.VizieR/J/AZh/81/541
Title:
Abundances of 15 solar analogues
Short Name:
J/AZh/81/541
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a spectroscopic analysis of 15 stars that are photometric analogues of the Sun are reported. The effective temperatures and surface gravities in the stellar atmospheres are derived from published photometric indices and the HIPPARCOS parallaxes. The abundances of 33 elements ranging from lithium to europium are analyzed based on high-dispersion spectra taken with the new Coude echelle spectrometer of the Terskol Observatory in the northern Caucasus. The main parameters of most of the stars agree with the data of an [Fe/H] catalog published in 2001. Our study of the chemical compositions of the sample stars indicates that photometric analogues of the Sun can be divided into three groups according to their elemental abundances: six stars have solar chemical composition, four have abundance excesses, and five have some abundance deficiencies. The sample contains two metal-deficient subgiants (HD 133002 and HD 225239).
344. Abundances of solar neighbourhood stars
ID:
ivo://CDS.VizieR/J/A+A/576/A113
Title:
Abundances of solar neighbourhood stars
Short Name:
J/A+A/576/A113
Date:
21 Oct 2021
Publisher:
CDS
Description:
A combined study of kinematics and chemical composition of stars is one of the most promising tools of research in Galaxy formation. The main goal in this field of research is to reconstruct the formation history of our Galaxy, to reveal the origin of the thick disc, and to find remnants of ancient mergers. We determine detailed elemental abundances in stars belonging to the so-called Group 1 of the Geneva-Copenhagen survey (GCS) and compare the chemical composition with the Galactic thin- and thick-disc stars, with the GCS Group 2 and Group 3 stars, as well as with several kinematic streams of similar metallicities. The aim is to search for chemical signatures that might give information about the formation history of this kinematic group of stars. High-resolution spectra were obtained with the Fibre-fed Echelle Spectrograph spectrograph at the Nordic Optical Telescope, La Palma, and were analysed with a differential model atmosphere method. Comparison stars were observed and analysed with the same method. The average value of [Fe/H] for the 37 stars of Group 1 is -0.20+/-0.14dex. Investigated Group 1 stars can be separated into three age subgroups. Along with the main 8- and 12-Gyr-old populations, a subgroup of stars younger than 5Gyr can be separated as well. Abundances of oxygen, {alpha}-elements, and r-process dominated elements are higher than in Galactic thin-disc dwarfs. This elemental abundance pattern has similar characteristics to that of the Galactic thick disc and differs slightly from those in Hercules, Arcturus, and AF06 stellar streams. The similar chemical composition of stars in Group 1, as well as in Group 2 and 3, with that in stars of the thick disc might suggest that their formation histories are linked. The chemical composition pattern together with the kinematic properties and ages of stars in the investigated GCS groups provide evidence of their common origin and possible relation to an ancient merging event. A gas-rich satellite merger scenario is proposed as the most likely origin.
345. Abundances of solar twins from Keck/HIRES
ID:
ivo://CDS.VizieR/J/ApJ/839/94
Title:
Abundances of solar twins from Keck/HIRES
Short Name:
J/ApJ/839/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
The six planets of the Kepler-11 system are the archetypal example of a population of surprisingly low-density transiting planets revealed by the Kepler mission. We have determined the fundamental parameters and chemical composition of the Kepler-11 host star to unprecedented precision using an extremely high-quality spectrum from Keck-HIRES (R~67000, S/N per pixel ~260 at 600nm). Contrary to previously published results, our spectroscopic constraints indicate that Kepler-11 is a young main-sequence solar twin. The revised stellar parameters and new analysis raise the densities of the Kepler-11 planets by between 20% and 95% per planet, making them more typical of the emerging class of "puffy" close-in exoplanets. We obtain photospheric abundances of 22 elements and find that Kepler-11 has an abundance pattern similar to that of the Sun with a slightly higher overall metallicity. We additionally analyze the Kepler light curves using a photodynamical model and discuss the tension between spectroscopic and transit/TTV-based estimates of stellar density.
346. Abundances of 93 solar-type Kepler targets
ID:
ivo://CDS.VizieR/J/MNRAS/423/122
Title:
Abundances of 93 solar-type Kepler targets
Short Name:
J/MNRAS/423/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed spectroscopic study of 93 solar-type stars that are targets of the NASA/Kepler mission and provide detailed chemical composition of each target. We find that the overall metallicity is well represented by Fe lines. Relative abundances of light elements (CNO) and {alpha} elements are generally higher for low-metallicity stars. Our spectroscopic analysis benefits from the accurately measured surface gravity from the asteroseismic analysis of the Kepler light curves. The accuracy on the log g parameter is better than 0.03dex and is held fixed in the analysis.
347. Abundances of 72 solar-type stars
ID:
ivo://CDS.VizieR/J/A+A/640/A81
Title:
Abundances of 72 solar-type stars
Short Name:
J/A+A/640/A81
Date:
29 Nov 2021 07:35:20
Publisher:
CDS
Description:
Previous high-precision studies of abundances of elements in solar twin stars are extended to a wider metallicity range to see how the trends of element ratios with stellar age depend on [Fe/H]. HARPS spectra with S/N>~600 at {lambda}~6000{AA} were analysed with MARCS model atmospheres to obtain 1D LTE abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Sr, and Y in 72 solar-type stars including the binary star zeta Reticuli and ASTEC stellar models were used to determine stellar ages from effective temperatures, luminosities obtained via Gaia DR2 parallaxes, and heavy element abundances. The age-metallicity distribution appears to consist of the following two distinct populations: a sequence of old stars with a steep rise of [Fe/H] to ~+0.3 dex at an age of ~7Gyr and a younger sequence with [Fe/H] increasing from about -0.3dex to ~+0.2dex over the last 6Gyr. Furthermore, the trends of several abundance ratios, [O/Fe], [Na/Fe], [Ca/Fe], and [Ni/Fe], as a function of stellar age, split into two corresponding sequences. The [Y/Mg]-age relation, on the other hand, shows no offset between the two age sequences and has no significant dependence on [Fe/H], but the components of a visual binary star, {zeta} Reticuli, have a large and puzzling deviation. The split of the age-metallicity distribution into two sequences may be interpreted as evidence of two episodes of accretion of gas onto the Galactic disk with a quenching of star formation in between. Some of the [X/Fe]-age relations support this scenario but other relations are not so easy to explain, which calls for a deeper study of systematic errors in the derived abundances as a function of [Fe/H], in particular 3D non-LTE effects.
348. Abundances of 9 solar-type stars
ID:
ivo://CDS.VizieR/J/A+A/327/587
Title:
Abundances of 9 solar-type stars
Short Name:
J/A+A/327/587
Date:
21 Oct 2021
Publisher:
CDS
Description:
Line identifications, measured equivalent widths and derived chemical abundances in 9 solar-type dwarf stars, which are identified by their Bright Star (HR, (Cat. <V/50>)) numbers.
349. Abundances of 7 southern-hemisphere Cepheids
ID:
ivo://CDS.VizieR/J/PAZh/37/781
Title:
Abundances of 7 southern-hemisphere Cepheids
Short Name:
J/PAZh/37/781
Date:
21 Oct 2021
Publisher:
CDS
Description:
For seven faint southern Cepheids (WW Car, SX Car, UZ Car, UY Car, GX Car, HW Car, YZ Car), we have determined their atmospheric parameters and chemical composition for the first time based on ten high-resolution (R=50000) spectra taken with the 1.5-m Hexapod telescope at the Joint Observatory of the Northern Catholic University (Antofagasta, Chile) and the Ruhr University (Bochum, Germany). Six objects from the list demonstrate atmospheric parameters and chemical composition typical of Cepheids that have passed through the first dredge-up phase, while WW Car is probably an anomalous Cepheid. According to our preliminary estimates, it has an overabundance of CNO, a deficit of sodium and aluminium, and a slight deficit of magnesium, with iron and other elements being underabundant relative to the Sun.
350. Abundances of Sr, Y, Zr, Ce and Ba
ID:
ivo://CDS.VizieR/J/AZh/84/997
Title:
Abundances of Sr, Y, Zr, Ce and Ba
Short Name:
J/AZh/84/997
Date:
21 Oct 2021
Publisher:
CDS
Description:
Sr, Y, Zr, and Ce abundances are derived for the sample of 74 cool dwarfs and subgiants with the iron abundance [Fe/H] ranged between -2.43 and 0.25. The results are based on LTE (Y, Zr and Ce) and non-LTE (Sr) line formation and line profile analysis of high resolution (40000 and 60000) spectra that have a typical S/N of 50-200. The Zr/Y, Sr/Y, and Sr/Zr ratios in the halo stars form nearly a plateau over the wide metallicity range, -2.43<=[Fe/H]<=0.90, indicating a common origin of Sr, Y, and Zr at the epoch of the halo formation. We find a steep decline of [Zr/Y] in the thick disk stars with increasing Ba abundance. This suggests the reduction of the production rate of Zr compared to that for Y at the active phase of the thick disk formation. The halo and thick disk stars reveal an overabundance of Zr relative to barium that grows with decreasing Ba abundance. There is a clear correlation of the [Zr/Ba] and [Eu/Ba] abundance ratios. Our observational findings for the halo and thick disk do not support the Galaxy chemical evolution models available in the literature and require to improve their predictions. The thin disk stars reveal, on average, solar abundance ratios for (Y,Zr)/Fe, (Y,Zr)/Ba, and Zr/Y. We note a slight decline of Zr/Ba and Zr/Y in these stars with increasing Ba abundance. Our results favour a dominance of the asymptotic giant branch stars in the heavy element enrichment of the interstellar gas over the epoch of the thin disk existence, in agreement with the theory of the main s-process nucleosynthesis.

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