- ID:
- ivo://CDS.VizieR/J/MNRAS/364/272
- Title:
- Elemental abundances in Blanco 1
- Short Name:
- J/MNRAS/364/272
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectroscopy is used to determine the detailed chemical abundances of a group of eight F- and G-type stars in the young open cluster Blanco 1. An average [Fe/H] of +0.04+/-0.02 (internal error)+/-0.04 (external error) is found, considerably lower than a previous spectroscopic estimate for this cluster. The difference is due mainly to our adoption of significantly cooler temperatures that are consistent with both photometric and spectroscopic constraints. Blanco 1 exhibits subsolar [Ni/Fe](0.18+/-0.01+/-0.01), [Si/Fe](0.09+/-0.02+/-0.03), [Mg/Fe](0.14+/-0.02+/-0.03) and [Ca/Fe](0.09+/-0.03+/-0.03); ratios that are not observed among nearby field stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/563
- Title:
- Elemental abundances in Hyades supercluster
- Short Name:
- J/MNRAS/415/563
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The existence of a kinematically defined moving group of stars centred at U=-40, V=-17km/s, referred to as the Hyades supercluster, has been suggested to be the debris of an originally large star-forming event, with its core being the present-day Hyades open cluster. Using high-resolution UV-Visual Echelle Spectrograph (UVES) spectra, we present the elemental abundances for a range of alpha, Fe-peak and neutron-capture elements for 26 proposed supercluster stars. Our results show that the sample stars display a heterogeneous abundance distribution, with a clump around [Fe/H]=+0.15. We also calculate stellar radial velocities and U, V, W space velocities. Enforcing strict chemical and kinematical membership criteria, we find that four supercluster stars share the Hyades open cluster abundances and kinematics, while many of the remaining stars fit the disc field kinematics and abundance range. We discuss our findings in the context of the Hyades supercluster being a dispersed star-forming remnant, a stellar stream of purely dynamical origin or a result of several processes.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A117
- Title:
- Equivalent widths for six M67 stars
- Short Name:
- J/A+A/627/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The benchmark open cluster M67 is known to have solar metallicity and similar age as the Sun. It thus provides us a great opportunity to study the properties of solar twins, as well as the evolution of Sun-like stars. Previous spectroscopic studies claimed to detect possible subtle changes in stellar surface abundances throughout the stellar evolutionary phase, namely the effect of atomic diffusion, in M67. In this study we attempt to confirm and quantify the effect of atomic diffusion, as well as to explore the level of chemical (in)homogeneity in M67. We presented a strictly line-by-line differential chemical abundance analysis of two groups of stars in M67: three turn-off stars and three sub-giants. Stellar atmospheric parameters and elemental abundances were obtained with very high precision using the Keck/HIRES spectra. The sub-giants in our sample show negligible abundance variations (<=0.02dex), which implies that M67 was born chemically homogeneous. We note there is a significant abundance difference (~0.1-0.2dex) between sub-giants and turn-off stars, which can be interpreted as the signature of atomic diffusion. Qualitatively stellar models with diffusion agree with the observed abundance results. Some turn-off stars do not follow the general pattern, which suggests that in some cases diffusion can be inhibited. Our results thus pose a challenge for chemical tagging using the turn-off stars since they are likely not chemically homogeneous. Meanwhile, our results suggest that the effect of atomic diffusion could be as large as 0.1-0.2dex, and must be taken into account when using the current surface abundances of stars for chemical tagging.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A120
- Title:
- Equivalent widths in 10 open clusters
- Short Name:
- J/A+A/588/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are distributed all across the disk and are convenient tracers of its properties. In particular, outer disk clusters bear a key role for the investigation of the chemical evolution of the Galactic disk. The goal of this study is to derive homogeneous elemental abundances for a sample of ten outer disk OCs, and investigate possible links with disk structures such as the Galactic Anticenter Stellar Structure. We analyse high-resolution spectra of red giants, obtained from the HIRES@Keck and UVES@VLT archives. We derive elemental abundances and stellar atmosphere parameters by means of the classical equivalent width method. We also performed orbit integrations using proper motions. The Fe abundances we derive trace a shallow negative radial metallicity gradient of slope -0.027+/-0.007dex/kpc in the outer 12kpc of the disk. The [alpha/Fe] gradient appears flat, with a slope of 0.006+/-0.007dex/kpc. The two outermost clusters (Be 29 and Sau 1) appear to follow elliptical orbits. Be 20 also exhibits a peculiar orbit with a large excursion above the plane. The irregular orbits of the three most metal-poor clusters (two of which are located at the edge of the Galactic disk), if confirmed by more robust astrometric measurements such as those of the Gaia mission, are compatible with an inside-out formation scenario for the Milky Way, in which extragalactic material is accreted onto the outer disk. We cannot determine if Be 20, Be 29, and Sau 1 are of extragalactic origin, as they may be old genuine Galactic clusters whose orbits were perturbed by accretion events or minor mergers in the past 5Gyr, or they may be representants of the thick disk population. The nature of these objects is intriguing and deserves further investigations in the near future.
- ID:
- ivo://CDS.VizieR/J/AJ/130/652
- Title:
- Equivalent widths of 4 giants in Be22 and Be66
- Short Name:
- J/AJ/130/652
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on high-resolution spectroscopy of four giant stars in the Galactic old open clusters Berkeley 22 and Berkeley 66 obtained with HIRES at the Keck telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/501/553
- Title:
- Equivalent widths of IC 2602 & IC 2391 stars
- Short Name:
- J/A+A/501/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic open clusters have been long recognized as one of the best tools to investigate the chemical content of Galactic disk and its time evolution. In the last decade, many efforts have been directed to chemically characterize the old and intermediate age population; surprisingly, the chemical content of the younger and close counterpart remains largely undetermined. In this paper we present the abundance analysis of a sample of 15 G/K members of the young pre-main sequence clusters IC 2602 and IC 2391. Along with IC 4665, these are the first pre-main sequence clusters for which a detailed abundance determination has been carried out so far.
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/3527
- Title:
- Equivalent widths of 11 NGC 3680 stars
- Short Name:
- J/MNRAS/422/3527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new abundance analysis of the intermediate-age Galactic open cluster NGC 3680, based on high-resolution, high signal-to-noise ratio VLT/UVES spectroscopic data. Several element abundances are presented for this cluster for the first time, but most notably we derive abundances for the light and heavy s-process elements Y, Ba, La and Nd. The serendipitous measurement of the rare-earth r-process element Gd is also reported. This cluster exhibits a significant enhancement of Na in giants as compared to dwarfs, which may be a proxy for an O to Na anticorrelation as observed in Galactic globular clusters but not open clusters. We also observe a step-like enhancement of heavy s-process elements towards higher atomic number, contrary to expectations from asymptotic giant branch nucleosynthesis models, suggesting that the r process played a significant role in the generation of both La and Nd in this cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A165
- Title:
- Equivalent widths of 13 red giants in IC 4756
- Short Name:
- J/A+A/615/A165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Homogeneous investigations of red giant stars in open clusters contribute to studies of internal evolutionary mixing processes inside stars, which are reflected in abundances of mixing-sensitive chemical elements like carbon, nitrogen, and sodium, while {alpha}- and neutron-capture element abundances are useful in tracing the Galactic chemical evolution. The main aim of this study is a comprehensive chemical analysis of red giant stars in the open cluster IC 4756, including determinations of ^12^C/^13^C and C/N abundance ratios, and comparisons of the results with theoretical models of stellar and Galactic chemical evolution. We used a classical differential model atmosphere method to analyse high-resolution spectra obtained with the FEROS spectrograph on the 2.2m MPG/ESO Telescope. The carbon, nitrogen, and oxygen abundances, ^12^C/^13^C ratios, and neutron-capture element abundances were determined using synthetic spectra, and the main atmospheric parameters and abundances of other chemical elements were determined from equivalent widths of spectral lines.
- ID:
- ivo://CDS.VizieR/J/AJ/139/1942
- Title:
- Equivalent widths of red giants in 6 open clusters
- Short Name:
- J/AJ/139/1942
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed abundance analysis based on high resolution spectroscopy for 16 stars in the old open clusters Be 31, Be 32, Be 39, M 67, NGC 188, and NGC 1193.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A66
- Title:
- Equivalent widths of 7 stars in NGC 6705
- Short Name:
- J/A+A/610/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar [{alpha}/Fe] abundance is sometimes used as a proxy for stellar age, following standard chemical evolution models for the Galaxy, as seen by different observational results. In this work we show that the Open Cluster NGC6705/M11 has a significant {alpha}-enhancement [{alpha}/Fe]>0.1dex, despite its young age (~300Myr), challenging the current paradigm.}{We use high resolution (R$>65,000$) high signal-to-noise (~70) spectra of 8 Red Clump stars, acquired within the OCCASO survey. We determine very accurate chemical abundances of several {alpha} elements, using an equivalent width methodology (Si, Ca and Ti), and spectral synthesis fits (Mg and O). We obtain [Si/Fe]=0.13+/-0.05, [Mg/Fe]=0.14+/-0.07, [O/Fe]=0.17+/-0.07, [Ca/Fe]=0.06+/-0.05 and [Ti/Fe]=0.03+/-0.03. Our results place these cluster within the group of young [{alpha}/Fe]-enhanced field stars recently found by several authors in the literature. The ages of our stars have an uncertainty of around 50Myr, much more precise than for field stars. By integrating the cluster's orbit in several non-axisymmetric Galactic potentials, we establish the M11's most likely birth radius to lie between 6.8-7.5kpc from the Galactic center, not far from its current position. With the robust Open Cluster age scale, our results prove that a moderate [{alpha}/Fe]-enhancement is no guarantee for a star to be old, and that not all {alpha}-enhanced stars can be explained with an evolved blue straggler scenario. Based on our orbit calculations, we further argue against a Galactic bar origin of M11.
