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291. Abundances of neutron-capture elements
ID:
ivo://CDS.VizieR/J/A+A/649/A126
Title:
Abundances of neutron-capture elements
Short Name:
J/A+A/649/A126
Date:
22 Feb 2022
Publisher:
CDS
Description:
The aim of this work is to determine abundances of neutron-capture elements for thin- and thick-disc F, G, and K stars in several selected sky fields near the North Ecliptic Pole and to compare the results with the Galactic chemical evolution models, to explore elemental gradients according to stellar ages, mean galactocentric distances, and maximum heights above the Galactic plane. The observational data were obtained with the 1.65 meter telescope at the Moletai Astronomical Observatory and a fibre-fed high-resolution spectrograph covering a full visible wavelength range (4000-8500{AA}). Elemental abundances were determined using a differential line-by-line spectrum synthesis using the TURBOSPECTRUM code with the MARCS stellar model atmospheres and accounting for the hyperfine-structure effects. Results. We determined abundances of Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, and Eu for 424 thin- and 82 thick-disc stars. The sample of thick-disc stars shows a clearly visible decrease of [Eu/Mg] with increasing metallicity compared to the thin-disc stars, bringing more evidences of different chemical evolution in these two Galactic components. Abundance correlation with age slopes for the investigated thin-disc stars are slightly negative for the majority of s-process dominated elements, while r-process dominated elements have positive correlations. Our sample of thin-disc stars with ages spanning from 0.1 to 9Gyrs gives the [Y/Mg]=0.022(+/-0.015)-0.027(+/-0.003)/age[Gyr] relation. However, for the thick-disc stars, when taking into account also data from other studies, we found that [Y/Mg] cannot serve as an age indicator. The radial abundance-to-iron gradients in the thin disc are negligible for the s-process dominated elements and become positive for the r-process dominated elements, the vertical gradients are negative for the light s-process dominated elements and become positive for the r-process dominated elements. In the thick disc, the radial abundance-to-iron slopes are negligible and the vertical ones are predominantly negative.
292. Abundances of 7 new member stars in Tucana II
ID:
ivo://CDS.VizieR/J/ApJ/857/74
Title:
Abundances of 7 new member stars in Tucana II
Short Name:
J/ApJ/857/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present chemical abundance measurements for seven stars with metallicities ranging from [Fe/H]=-3.3 to [Fe/H]=-2.4 in the TucanaII ultra-faint dwarf galaxy (UFD), based on high-resolution spectra obtained with the MIKE spectrograph on the 6.5m Magellan-Clay Telescope. For three stars, we present detailed chemical abundances for the first time. Of those, two stars are newly discovered members of Tucana II and were selected as probable members from deep narrowband photometry of the Tucana II UFD taken with the SkyMapper telescope. This result demonstrates the potential for photometrically identifying members of dwarf galaxy systems based on chemical composition. One new star was selected from the membership catalog of Walker+ (2016, J/ApJ/819/53). The other four stars in our sample have been reanalyzed, following additional observations. Overall, six stars have chemical abundances that are characteristic of the UFD stellar population. The seventh star shows chemical abundances that are discrepant from the other Tucana II members and an atypical, higher strontium abundance than what is expected for typical UFD stars. While unlikely, its strontium abundance raises the possibility that it may be a foreground metal-poor halo star with the same systemic velocity as Tucana II. If we were to exclude this star, Tucana II would satisfy the criteria to be a surviving first galaxy. Otherwise, this star implies that Tucana II has likely experienced somewhat extended chemical evolution.
293. Abundances of NGC 7142, 6939, and IC 4756 stars
ID:
ivo://CDS.VizieR/J/AJ/134/1216
Title:
Abundances of NGC 7142, 6939, and IC 4756 stars
Short Name:
J/AJ/134/1216
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of echelle spectra of stars in three open clusters obtained with the Hydra multiobject spectrograph on the WIYN 3.5m telescope. Abundances of Fe, O, Si, Ca, Na, Al, and Ni have been determined via equivalent width analysis and spectrum synthesis. Mean abundances for each cluster are compared to those of previous studies and of other clusters in the literature, with emphasis on exploring the enhancements of Na and Al seen in many open clusters. All three clusters show enhanced values of [Na/Fe] and [Al/Fe], while the abundances of Fe, O, Si, and Ca are consistent with their ages and locations in the Galactic disk.
294. Abundances of NGC 7789 evolved stars
ID:
ivo://CDS.VizieR/J/A+A/431/933
Title:
Abundances of NGC 7789 evolved stars
Short Name:
J/A+A/431/933
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-resolution spectra of six giants and three core-helium-burning "clump" stars in the open cluster NGC 7789 have been obtained with the SOFIN spectrograph on the Nordic Optical Telescope to investigate abundances of up to 20 chemical elements. Abundances of carbon were studied using the C_2_ Swan (0, 1) band head at 5635.5{AA}. The wavelength interval 7980-8130{AA} with strong CN features was analysed in order to determine nitrogen abundances and ^12^C/^13^C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300{AA}.
295. Abundances of NGC 6362 member stars
ID:
ivo://CDS.VizieR/J/ApJ/824/73
Title:
Abundances of NGC 6362 member stars
Short Name:
J/ApJ/824/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first measure of Fe and Na abundances in NGC 6362, a low-mass globular cluster (GC) where first- and second-generation stars are fully spatially mixed. A total of 160 member stars (along the red giant branch (RGB) and the red horizontal branch (RHB)) were observed with the multi-object spectrograph FLAMES at the Very Large Telescope. We find that the cluster has an iron abundance of [Fe/H]=-1.09+/-0.01dex, without evidence of intrinsic dispersion. On the other hand, the [Na/Fe] distribution turns out to be intrinsically broad and bimodal. The Na-poor and Na-rich stars populate, respectively, the bluest and the reddest RGBs detected in the color-magnitude diagrams including the U filter. The RGB is composed of a mixture of first- and second-generation stars in a similar proportion, while almost all the RHB stars belong to the first cluster generation. To date, NGC 6362 is the least massive GC where both the photometric and spectroscopic signatures of multiple populations have been detected.
296. Abundances of NGC5897 red giants
ID:
ivo://CDS.VizieR/J/A+A/565/A23
Title:
Abundances of NGC5897 red giants
Short Name:
J/A+A/565/A23
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report for the first time on the chemical composition of the halo cluster NGC 5897 (R_{sun}_=12.5kpc), based on chemical abundance ratios for 27 {alpha}-, iron-peak, and neutron-capture elements in seven red giants. From our high-resolution, high signal-to-noise spectra obtained with theMagellan/MIKE spectrograph, we find a mean iron abundance from the neutral species of [Fe/H]=-2.04+/-0.01(stat.)+/-0.15(sys.), which is more metal-poor than implied by previous photometric and low-resolution spectroscopic studies. NGC 5897 is {alpha}-enhanced (to 0.34+/-0.01dex) and shows Fe-peak element ratios typical of other (metal-poor) halo globular clusters (GCs) with no overall, significant abundance spreads in iron nor in any other heavy element.
297. Abundances of NGC 6121 red giants
ID:
ivo://CDS.VizieR/J/A+A/490/625
Title:
Abundances of NGC 6121 red giants
Short Name:
J/A+A/490/625
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present abundance analysis based on high resolution spectra of 105 isolated red giant branch (RGB) stars in the Galactic Globular Cluster NGC 6121 (M4). The data have been collected with FLAMES+UVES, at the ESO/VLT@UT2 telescope. Spectroscopic data were coupled with high precision wide-field UBVI_C photometry from WFI@2.2m telescope and infrared JHK photometry from 2MASS. We derived an average [Fe/H]=-1.07+/-0.01, and an {alpha} enhancement of [{alpha}/Fe]=+0.39+/-0.05dex (internal errors). We confirm the presence of an extended Na-O anticorrelation, and find two distinct groups of stars with significantly different Na and O content. We find no evidence of a Mg-Al anticorrelation. By coupling our results with previous studies on the CN band strength, we find that the CN strong stars have higher Na and Al content and are more O depleted than the CN weak ones. The two groups of Na-rich, CN-strong and Na-poor, CN-weak stars populate two different regions along the RGB. In the U vs. U-B color magnitude diagram the RGB spread is present from the base of the RGB to the RGB-tip. Apparently, both spectroscopic and photometric results imply the presence of two stellar populations in M4. We briefly discuss the possible origin of these populations.
298. Abundances of non-type I PNe in LMC
ID:
ivo://CDS.VizieR/J/A+A/279/567
Title:
Abundances of non-type I PNe in LMC
Short Name:
J/A+A/279/567
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectroscopic observations, plasma diagnostics and chemical composition of 15 non-type I planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) are reported. Abundances of He, O, N, S, and Ar are determined and compared with recently obtained data for nebulae both in the Magellanic Clouds and in the Galaxy.
299. Abundances of non-variable red and blue HB stars
ID:
ivo://CDS.VizieR/J/AJ/140/1694
Title:
Abundances of non-variable red and blue HB stars
Short Name:
J/AJ/140/1694
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new detailed abundance study of field red horizontal branch (RHB) and blue horizontal branch (BHB) non-variable stars. High resolution and high signal-to-noise ratio echelle spectra of 11 RHB and 12 BHB were obtained with the McDonald 2.7m telescope, and the RHB sample was augmented by reanalysis of spectra of 25 stars from a recent survey. We derived stellar atmospheric parameters based on spectroscopic constraints and computed relative abundance ratios for 24 species of 19 elements.
300. Abundances of ONC X-ray PMS stars
ID:
ivo://CDS.VizieR/J/ApJ/660/1462
Title:
Abundances of ONC X-ray PMS stars
Short Name:
J/ApJ/660/1462
Date:
21 Oct 2021
Publisher:
CDS
Description:
Following the Chandra Orion Ultradeep Project (COUP) observation, we have studied the chemical composition of the hot plasma in a sample of 146 X-ray-bright pre-main-sequence stars in the Orion Nebula Cluster (ONC). We report measurements of individual element abundances for a subsample of 86 slightly absorbed and bright X-ray sources, using low-resolution X-ray spectra obtained from the Chandra ACIS instrument.

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