- ID:
- ivo://CDS.VizieR/J/AJ/148/67
- Title:
- Abundances of 156 bulge red giants
- Short Name:
- J/AJ/148/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch stars in two Galactic bulge fields centered near (l,b)=(+5.25,-3.02) and (0,-12). The (+5.25,-3.02) field also includes observations of the bulge globular cluster NGC 6553. The results are based on high-resolution (R~20000), high signal-to-noise ration (S/N>~70) FLAMES-GIRAFFE spectra obtained through the European Southern Observatory archive. However, we only selected a subset of the original observations that included spectra with both high S/N and that did not show strong TiO absorption bands. This work extends previous analyses of this data set beyond Fe and the {alpha}-elements Mg, Si, Ca, and Ti. While we find reasonable agreement with past work, the data presented here indicate that the bulge may exhibit a different chemical composition than the local thick disk, especially at [Fe/H]>~-0.5. In particular, the bulge [{alpha}/Fe] ratios may remain enhanced to a slightly higher [Fe/H] than the thick disk, and the Fe-peak elements Co, Ni, and Cu appear enhanced compared to the disk. There is also some evidence that the [Na/Fe] (but not [Al/Fe]) trends between the bulge and local disk may be different at low and high metallicity. We also find that the velocity dispersion decreases as a function of increasing [Fe/H] for both fields, and do not detect any significant cold, high-velocity populations. A comparison with chemical enrichment models indicates that a significant fraction of hypernovae may be required to explain the bulge abundance trends, and that initial mass functions that are steep, top-heavy (and do not include strong outflow), or truncated to avoid including contributions from stars >40M_{sun}_ are ruled out, in particular because of disagreement with the Fe-peak abundance data. For most elements, the NGC 6553 stars exhibit abundance trends nearly identical to comparable metallicity bulge field stars. However, the star-to-star scatter and mean [Na/Fe] ratios appear higher in the cluster, perhaps indicating additional self-enrichment.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/530/A54
- Title:
- Abundances of 650 bulge red giants
- Short Name:
- J/A+A/530/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the [alpha/Fe] abundance ratios for a large number of stars at several locations in the Milky Way bulge with the aim of constraining its formation scenario. We obtained FLAMES-GIRAFFE spectra (R=22500) at the ESO Very Large Telescope for 650 bulge red giant branch (RGB) stars and performed spectral synthesis to measure Mg, Ca, Ti, and Si abundances. This sample is composed of 474 giant stars observed in 3 fields along the minor axis of the Galactic bulge and at latitudes b=-4{deg}, b=-6{deg}, b=-12{deg}. Another 176 stars belong to a field containing the globular cluster NGC 6553, located at b=-3{deg} and 5{deg} away from the other three fields along the major axis.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A34
- Title:
- Abundances of carbon-enhanced metal-poor stars
- Short Name:
- J/A+A/548/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of Carbon-Enhanced Metal-Poor (CEMP) stars, based on high-resolution spectroscopic observations of a sample of 18 stars. The stellar spectra for this sample were obtained at the 4.2m William Herschel Telescope (WHT) in 2001 and 2002, using the Utrecht Echelle Spectrograph (UES), at a resolving power R~52000 and S/N~40, covering the wavelength range {lambda}-{lambda}3700-5700{AA}. The atmospheric parameters determined for this sample indicate temperatures ranging from 4750K to 7100K, log g from 1.5 to 4.3, and metallicities -3.0<=[Fe/H]<=-1.7. Elemental abundances for C, Na, Mg, Sc, Ti, Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, Gd, Dy are determined. Abundances for an additional 109 stars were taken from the literature and combined with the data of our sample. The literature sample reveals a lack of reliable abundance estimates for species that might be associated with the r-process elements for about 67% of CEMP stars, preventing a complete understanding of this class of stars, since [Ba/Eu] ratios are used to classify them. Although eight stars in our observed sample are also found in the literature sample, Eu abundances or limits are determined for four of these stars for the first time. From the observed correlations between C, Ba, and Eu, we argue that the CEMP-r/s class has the same astronomical origin as CEMP-s stars, highlighting the need for a more complete understanding of Eu production.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/367
- Title:
- Abundances of carbon stars in Galactic halo
- Short Name:
- J/ApJ/658/367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is known that the carbon-enhanced, extremely metal-poor (CEMP) stars constitute a substantial proportion of the extremely metal-poor (EMP) stars of the Galactic halo, and a by far larger proportion than CH stars among Population II stars. We investigate their origin by taking into account an additional evolutionary path to the surface carbon enrichment, triggered by hydrogen engulfment by the helium flash convection, in EMP stars with [Fe/H]<~-2.5. This process is distinct from the third dredge-up operating in more metal-rich stars and in EMP stars. In binary systems of EMP stars, the secondary stars become CEMP stars through mass transfer from the low- and intermediate- mass primary stars that have developed the surface carbon enhancement. Our binary scenario can predict the variations in the abundances not only for carbon but also for nitrogen and s-process elements and can reasonably explain the observed properties such as the stellar distributions of the carbon abundances, the binary periods, and the evolutionary stages.
- 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.
- 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/AJ/132/902
- Title:
- Abundances of 54 Cepheids
- Short Name:
- J/AJ/132/902
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the spectroscopic investigation of 54 Cepheids, deriving parameters and abundances. These Cepheids extend previous samples by about 35% in number and increase the amount of the Galactic disk coverage, especially in the direction of l~120{deg}. We find that there exists in the Galactic disk at that longitude and at a solar distance of about 3-4kpc a region that has enhanced abundances, <[Fe/H]>~+0.2, with respect to the local region. A simple linear fit to all Cepheid data now extant yields a gradient d[Fe/H]/dR=-0.068+/-0.003dex/kpc. After consideration of the spatial abundance inhomogeneities in the sample, we conclude that the best current estimate of the overall gradient is d[Fe/H]/dR=-0.06dex/kpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/1590
- Title:
- Abundances of classical Cepheids
- Short Name:
- J/MNRAS/420/1590
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose a statistical method for decomposition of contributions to iron production from various sources: Type II supernovae and the subpopulations of Type Ia supernovae, prompt (their progenitors are short-lived stars with ages lower than >100Myr) and tardy (their progenitors are long-lived stars with ages >100Myr). To do that, we develop a theory of oxygen and iron synthesis that takes into account the influence of the spiral arms on the amount of the above elements synthesized by both Type II supernovae and prompt Type Ia supernovae. In the framework of the theory, we processed statistically the new, more precise, observational data on Cepheid abundances, which, as is well known, demonstrate non-trivial radial distributions of oxygen and iron in the Galactic disc with bends in the gradients.
- ID:
- ivo://CDS.VizieR/J/A+A/345/430
- Title:
- Abundances of 6 cool supergiants in NGC 330
- Short Name:
- J/A+A/345/430
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 330 is the brightest SMC young cluster and contains many bright supergiants. This cluster has aroused special interest, since the earlier abundance determinations indicated an abundance lower by a factor 5 than in the SMC field young population. In this Paper we analyse high resolution spectra of 6 cool supergiants in NGC 330, and compare in an homogeneous way, the metallicity and abundance ratios of various elements in NGC 330 and in the field of the SMC. The following Table is the Apendix to this Paper, giving the line list used in the analysis, together with the measured equivalent width and the derived abundance for each of the 6 stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/L32
- Title:
- Abundances of 16 Cyg A and B
- Short Name:
- J/ApJ/737/L32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a detailed abundance analysis of the solar twins 16 Cyg A and 16 Cyg B based on high-resolution, high signal-to-noise ratio echelle spectroscopy are presented. 16 Cyg B is known to host a giant planet while no planets have yet been detected around 16 Cyg A. Stellar parameters are derived directly from our high-quality spectra, and the stars are found to be physically similar, with {Delta}T_eff_=+43K, {Delta}logg=-0.02dex, and {Delta}{xi}=+0.10km/s (in the sense of A-B), consistent with previous findings. Abundances of 15 elements are derived and are found to be indistinguishable between the two stars. The abundances of each element differ by <=0.026dex, and the mean difference is +0.003+/-0.015({sigma}) dex. Aside from Li, which has been previously shown to be depleted by a factor of at least 4.5 in 16 Cyg B relative to 16 Cyg A, the two stars appear to be chemically identical. The abundances of each star demonstrate a positive correlation with the condensation temperature of the elements (T_c_); the slopes of the trends are also indistinguishable. In accordance with recent suggestions, the positive slopes of the [m/H]-T_c_ relations may imply that terrestrial planets have not formed around either 16 Cyg A or 16 Cyg B.
