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251. Abundances of giants in four Galactic clusters
ID:
ivo://CDS.VizieR/J/A+A/488/943
Title:
Abundances of giants in four Galactic clusters
Short Name:
J/A+A/488/943
Date:
21 Oct 2021
Publisher:
CDS
Description:
To constrain the formation and chemical evolution of the Galactic disk, we surveyed open clusters of different ages, metal contents, and distances form the Galactic centre. We employed FLAMES on VLT-UT2 to collect UVES spectra of bright giant stars in each of the selected clusters, and used them to derive the iron abundance and the detailed chemical composition. Equivalent widths were measured and abundance analysis was performed using the MOOG code and Kurucz model atmospheres. We derived the abundance of Fe for Mg, Al, Ca, Si, Ti, Cr, Ni, and Ba. We employed direct line profile fitting to derive non-LTE Na abundances. We found [Fe/H]=-0.30, -0.31, +0.13, -0.33 for Be 20, Be 29, Cr 261, and Melotte 66, respectively (with rms values of 0.02 to 0.05dex). Alpha- and Fe-peak elements have solar ratios, Ba is enhanced, and Na has solar ratios, suggesting that treatment of non-LTE is very important. We confirm the presence of a metallicity gradient in the inner disk, and a flattening in the outer part.
252. Abundances of 16 giants in M75
ID:
ivo://CDS.VizieR/J/A+A/554/A81
Title:
Abundances of 16 giants in M75
Short Name:
J/A+A/554/A81
Date:
21 Oct 2021
Publisher:
CDS
Description:
M75 is a relatively young Globular Cluster (GC) found at 15kpc from the Galactic centre at the transition region between the inner and outer Milky Way halos. Our aims are to perform a comprehensive abundance study of a variety of chemical elements in this GC such as to investigate its chemical enrichment history in terms of early star formation, and to search for any multiple populations. We have obtained high resolution spectroscopy with the MIKE instrument at the Magellan telescope for 16 red giant stars. Their membership within the GC is confirmed from radial velocity measurements. Our chemical abundance analysis is performed via equivalent width measurements and spectral synthesis, assuming local thermodynamic equilibrium (LTE). We present the first comprehensive abundance study of M75 to date. The cluster is metal-rich ([Fe/H]=-1.16+/-0.02dex, [alpha/Fe]=+0.30+/-0.02dex), and shows a marginal spread in [Fe/H] of 0.07dex, typical of most GCs of similar luminosity. A moderately extended O-Na anticorrelation is clearly visible, likely showing three generations of stars, formed on a short timescale. Additionally the two most Na-rich stars are also Ba-enhanced by 0.4 and 0.6dex, respectively, indicative of pollution by lower mass (M~4-5M_{sun}_) Asymptotic Giant Branch (AGB) stars. The overall n-capture element pattern is compatible with predominant r-process enrichment, which is rarely the case in GCs of such a high metallicity.
253. Abundances of 92 giants in Plaut's window
ID:
ivo://CDS.VizieR/J/ApJ/732/108
Title:
Abundances of 92 giants in Plaut's window
Short Name:
J/ApJ/732/108
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Fe, Si, and Ca abundances for 61 giants in Plaut's window (l=-1{deg}, b=-8.5{deg}) and Fe abundances for an additional 31 giants in a second, nearby field (l=0{deg}, b=-8{deg}) derived from high-resolution (R~25000) spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. The median metallicity of red giant branch (RGB) stars in the Plaut's field is ~0.4dex lower than those in Baade's window, and confirms the presence of an iron abundance gradient along the bulge minor axis. The full metallicity range of our (biased) RGB sample spans -1.5<[Fe/H]<+0.3, which is similar to that found in other bulge fields. We also derive a photometric metallicity distribution function for RGB stars in the (l=-1{deg}, b=-8.5{deg}) field and find very good agreement with the spectroscopic metallicity distribution. The radial velocity (RV) and dispersion data for the bulge RGB stars are in agreement with previous results of the Bulge Radial Velocity Assay survey, and we find evidence for a decreasing velocity dispersion with increasing [Fe/H]. The [{alpha}/Fe] enhancement in Plaut field stars is nearly identical to that observed in Baade's window, and suggests that an [{alpha}/Fe] gradient does not exist between b=-4{deg} and -8{deg}. Additionally, a subset of our sample (23 stars) appears to be foreground red clump stars that are very metal rich, exhibit small metallicity and RV dispersions, and are enhanced in {alpha} elements. While these stars likely belong to the Galactic inner disk population, they exhibit [{alpha}/Fe] ratios that are enhanced above the thin and thick disk.
254. Abundances of 848 giants of {omega} Cen
ID:
ivo://CDS.VizieR/J/MNRAS/433/1892
Title:
Abundances of 848 giants of {omega} Cen
Short Name:
J/MNRAS/433/1892
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the effective temperatures, surface gravities and abundances of iron, carbon and barium of 848 giant branch stars, of which 557 also have well-defined nitrogen abundances, of the globular cluster {omega} Centauri. This work used photometric sources and lower resolution spectra for this abundance analysis. Spectral indices were used to estimate the oxygen abundance of the stars, leading to a determination of whether a particular star was oxygen rich or oxygen poor. The 557-star subset was analysed in the context of evolutionary groups, with four broad groups identified. These groups suggest that there were at least four main periods of star formation in the cluster. The exact order of these star formation events is not yet understood. These results compare well with those found at higher resolution and show the value of more extensive lower resolution spectral surveys. They also highlight the need for large samples of stars when working with a complex object like {omega} Cen.
255. Abundances of halo early-type stars
ID:
ivo://CDS.VizieR/J/A+A/347/69
Title:
Abundances of halo early-type stars
Short Name:
J/A+A/347/69
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present echelle (R~40,000) spectroscopic observations for a sample of apparently normal, high Galactic latitude, early-type stars drawn from the Palomar-Green Survey. The metal-line spectra show evidence for rotational velocity broadening with values of vsini<=300km/s. In conjunction with Kurucz model atmospheres, we derive stellar photospheric abundances that are consistent with a Population I chemical composition; differential abundances with respect to Galactic disk Population I stars indicate no abundance differences outside the estimated errors. From a comparison of the derived atmospheric parameters with recent theoretical evolutionary models, we derive distance and age estimates for individual stars. Using kinematical considerations, we conclude that all these objects are `runaway' stars, formed in the Galactic disk and subsequently ejected, possibly by supernovae explosions or dynamical interactions.
256. Abundances of 9 HB stars in NGC 6352
ID:
ivo://CDS.VizieR/J/A+A/493/913
Title:
Abundances of 9 HB stars in NGC 6352
Short Name:
J/A+A/493/913
Date:
21 Oct 2021
Publisher:
CDS
Description:
Metal-rich globular clusters provide important tracers of the formation of our Galaxy. Moreover, and not less important, they are very important calibrators for the derivation of properties of extra-galactic metal-rich stellar populations. Nonetheless, only a few of the metal-rich globular clusters in the Milky Way have been studied using high-resolution stellar spectra to derive elemental abundances. Additionally, Rosenberg et al. identified a small group of metal-rich globular clusters that appeared to be about 2 billion years younger than the bulk of the Milky Way globular clusters. However, it is unclear if like is compared with like in this dataset as we do not know the enhancement of alpha-elements in the clusters and the amount of alpha-elements is well known to influence the derivation of ages for globular clusters. We present a study of elemental abundances for alpha and iron-peak elements for nine HB stars in the metal-rich globular cluster NGC 6352. The elemental abundances are based on high-resolution, high signal-to-noise spectra obtained with the UVES spectrograph on VLT. The elemental abundances have been derived using standard LTE calculations and stellar parameters have been derived from the spectra themselves by requiring ionizational as well as excitational equilibrium. We find that NGC 6352 has [Fe/H]=-0.55, is enhanced in the alpha-elements to about +0.2dex for Ca, Si, and Ti relative to Fe. For the iron-peak elements we find solar values. Based on the spectroscopically derived stellar parameters we find that an E(B-V)=0.24 and (m-M).
257. Abundances of HD221170
ID:
ivo://CDS.VizieR/J/A+A/430/255
Title:
Abundances of HD221170
Short Name:
J/A+A/430/255
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the abundance determination in the atmosphere of the bright halo star HD 221170. The spectra were taken with the Terskol Observatory's 2.0-m telescope with a resolution R=45000 and signal-to-noise ratio up to 250 in the wavelength region 3638-10275{AA}. The abundances of 43 chemical elements were determined with the method of spectrum synthesis.
258. Abundances of HD 221170
ID:
ivo://CDS.VizieR/J/ApJ/645/613
Title:
Abundances of HD 221170
Short Name:
J/ApJ/645/613
Date:
21 Oct 2021
Publisher:
CDS
Description:
Employing high-resolution spectra obtained with the near-UV-sensitive detector on the Keck I HIRES, supplemented by data obtained with the McDonald Observatory 2d-coude, we have performed a comprehensive chemical composition analysis of the bright r-process-rich metal-poor red giant star HD 221170. Analysis of 57 individual neutral and ionized species yielded abundances for a total of 46 elements and significant upper limits for an additional five. Model stellar atmosphere parameters were derived with the aid of ~200 Fe peak transitions. From more than 350 transitions of 35 neutron-capture (Z>30) species, abundances for 30 neutron-capture elements and upper limits for three others were derived. Utilizing 36 transitions of La, 16 of Eu, and seven of Th, we derive ratios of log{epsilon}(Th/La)=-0.73 ({sigma}=0.06) and log{epsilon}(Th/Eu)=-0.60 ({sigma}=0.05), values in excellent agreement with those previously derived for other r-process-rich metal-poor stars such as CS 22892-052, BD +17 3248, and HD 115444. Based on the Th/Eu chronometer, the inferred age is 11.7+/-2.8Gyr. The abundance distribution of the heavier neutron-capture elements (Z>=56) is fitted well by the predicted scaled solar system r-process abundances, as also seen in other r-process-rich stars. Unlike other r-process-rich stars, however, we find that the abundances of the lighter neutron-capture elements (37<Z<56) in HD 221170 are also in agreement with the abundances predicted for the scaled solar r-process pattern.
259. Abundances of HD 134439/40 and HD 211998
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.
260. Abundances of HDE 341617
ID:
ivo://CDS.VizieR/J/A+A/368/250
Title:
Abundances of HDE 341617
Short Name:
J/A+A/368/250
Date:
21 Oct 2021
Publisher:
CDS
Description:
Detailed atmospheric abundances have been calculated for a sample of A-G supergiant stars with IR fluxes and/or high galactic latitudes. HD 172481 and HD 158616 show clear indications of being post-AGB stars that have experienced third dredge-up. HD 158616 is carbon-rich while the abundance pattern of HD 172481 and its large Li enhancement gives support to the hot bottom burning scenario that explains paucity of carbon-rich stars among AGB stars. HD 172324 is very likely a hot post-AGB star that shows a strong carbon deficiency. HD 725, HD 218753 and HD 331319 also appear to be evolved objects between the red giant and the AGB. HD 9167, HD 173638 with a few exceptions, reflect solar abundances and no signs of post red giant evolution. They are most likely young massive disk supergiants. Further analysis of proto-Planetary Nebula HDE 341617 reveals that He lines show signs of velocity stratification. The emission lines have weakened considerably since 1993. The envelope expands at 19km/s relative to the star. Atmospheric abundances, evolutionary tracks and isochrones are used to estimate masses and ages of all stars in the sample.

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