- ID:
- ivo://CDS.VizieR/J/A+A/588/A98
- Title:
- Metallicities and abundances of evolved stars
- Short Name:
- J/A+A/588/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed chemical abundance studies have revealed different trends between samples of planet and non-planet hosts. Whether these trends are related to the presence of planets or not is strongly debated. At the same time, tentative evidence that the properties of evolved stars with planets may be different from what we know for main-sequence hosts has been recently reported. We aim to test whether evolved stars with planets show any chemical peculiarity that could be related to the planet formation process. We determine in a consistent way the metallicity and individual abundances of a large sample of evolved (subgiants and red giants) and main-sequence stars with and without known planetary companions, and discuss their metallicity distribution and trends. Our methodology is based on the analysis of high-resolution echelle spectra (R ~ 57000) from 2-3 m class telescopes. It includes the calculation of the fundamental stellar parameters, as well as, individual abundances.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/494/396
- Title:
- Metallicity distribution in GC
- Short Name:
- J/MNRAS/494/396
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present stellar metallicity measurements of more than 600 late-type stars in the central 10pc of the Galactic Centre. Together with our previously published KMOS data, this data set allows us to investigate, for the first time, spatial variations of the nuclear star cluster's metallicity distribution. Using the integral-field spectrograph KMOS (VLT), we observed almost half of the area enclosed by the nuclear star cluster's effective radius. We extract spectra at medium spectral resolution and apply full spectral fitting utilizing the PHOENIX library of synthetic stellar spectra. The stellar metallicities range from [M/H]=-1.25dex to [M/H]>+0.3dex, with most of the stars having supersolar metallicity. We are able to measure an anisotropy of the stellar metallicity distribution. In the Galactic north, the portion of subsolar metallicity stars with [M/H]<0.0dex is more than twice as high as in the Galactic south. One possible explanation for different fractions of subsolar metallicity stars in different parts of the cluster is a recent merger event. We propose to test this hypothesis with high- resolution spectroscopy and by combining the metallicity information with kinematic data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/194
- Title:
- Metallicity distribution in the GC
- Short Name:
- J/MNRAS/464/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowing the metallicity distribution of stars in the Galactic Centre has important implications for the formation history of the Milky Way nuclear star cluster. However, this distribution is not well known, and is currently based on a small sample of fewer than 100 stars. We obtained near-infrared K-band spectra of more than 700 late-type stars in the central 4pc^2^ of the Milky Way nuclear star cluster with the integral-field spectrograph KMOS (VLT). We analyse the medium-resolution spectra using a full-spectral fitting method employing the Gottingen spectral library of synthetic PHOENIX spectra. The derived stellar metallicities range from metal-rich [M/H]>+0.3dex to metal-poor [M/H]<-1.0dex, with a fraction of 5.2^+6.0^_-3.1_ per cent metal-poor ([M/H]<=-0.5dex) stars. The metal-poor stars are distributed over the entire observed field. The origin of metal-poor stars remains unclear. They could originate from infalling globular clusters. For the metal-rich stellar population ([M/H]>0dex), a globular cluster origin can be ruled out. As there is only a very low fraction of metal-poor stars in the central 4pc^2^ of the Galactic Centre, we believe that our data can discard a scenario in which the Milky Way nuclear star cluster is purely formed from infalling globular clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A36
- Title:
- Metallicity of M dwarfs. III.
- Short Name:
- J/A+A/551/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this work is the study of the planet-metallicity and the planet-stellar mass correlations for M dwarfs from the HARPS GTO M dwarf subsample. We use a new method that takes advantage of the HARPS high-resolution spectra to increase the precision of metallicity, using previous photometric calibrations of [Fe/H] and effective temperature as starting values.
- ID:
- ivo://CDS.VizieR/J/A+A/541/A40
- Title:
- Metallicity of solar-type stars
- Short Name:
- J/A+A/541/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Around 16% of the solar-like stars in our neighbourhood show IR-excesses due to dusty debris discs and a fraction of them are known to host planets. Determining whether these stars follow any special trend in their properties is important to understand debris disc and planet formation. We aim to determine in a homogeneous way the metallicity of a sample of stars with known debris discs and planets. We attempt to identify trends related to debris discs and planets around solar-type stars Our analysis includes the calculation of the fundamental stellar parameters Teff, logg, microturbulent velocity, and metallicity by applying the iron ionisation equilibrium conditions to several isolated FeI and FeII lines. High-resolution echelle spectra (R~57000) from 2, 3m class telescopes are used. Our derived metallicities are compared with other results in the literature, which finally allows us to extend the stellar samples in a consistent way.
- ID:
- ivo://CDS.VizieR/J/A+A/535/A42
- Title:
- Metal rich stars in solar neighbourhood
- Short Name:
- J/A+A/535/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The analysis of 71 metal-rich stars is based on optical high-resolution echelle spectra obtained with the FEROS spectrograph at the ESO 1.52-m Telescope at La Silla, Chile. The metallicities and abundances of C, O, Mg, Si, Ca, and Ti were derived based on LTE detailed analysis, employing the MARCS model atmospheres. We confirm the high metallicity of these stars reaching up to [FeI/H]=0.58, and the sample of metal-rich dwarfs can be kinematically subclassified in samples of thick disk, thin disk, and intermediate stellar populations. All sample stars show solar alpha-Fe ratios, and most of them are old and still quite metal rich. The orbits suggest that the thin disk, thick disk and intermediate populations were formed at Galactocentric distances of ~8kpc, ~6kpc, and ~7kpc, respectively. The mean maximum height of the thick disk subsample of Z_max_~380pc, is lower than for typical thick disk stars. A comparison of alpha-element abundances of the sample stars with bulge stars shows that the oxygen is compatible with a bulge or inner thick disk origin. Our results suggest that models of radial mixing and dynamical effects of the bar and bar/spiral arms might explain the presence of these old metal-rich dwarf stars in the solar neighbourhood.
- ID:
- ivo://CDS.VizieR/J/A+A/430/303
- Title:
- MgII-K line fluxes in cool active and quiet stars
- Short Name:
- J/A+A/430/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The MgIIk emission line is a good indicator of the level of chromospheric activity in late-type stars. We investigate the dependence of this activity indicator on fundamental stellar parameters. To this purpose we use IUE observations of the MgIIk line in 225 late-type stars of luminosity classes I-V, with different levels of chromospheric activity. We first re-analyse the relation between MgIIk line luminosity and stellar absolute magnitude, performing linear fits to the points. The ratio of MgII surface flux to total surface flux is found to be independent of stellar luminosity for evolved stars and to increase with decreasing luminosity for dwarfs. We also analyse the MgIIk line surface flux-metallicity connection.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/1627
- Title:
- Mid-IR photometry of cold brown dwarfs
- Short Name:
- J/ApJ/710/1627
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Spitzer Infrared Array Camera (IRAC) photometry of 12 very late-type T dwarfs: nine have [3.6], [4.5], [5.8], and [8.0] photometry and three have [3.6] and [4.5] photometry only. Combining this with previously published photometry, we investigate trends with type and color that are useful for both the planning and interpretation of infrared surveys designed to discover the coldest T or Y dwarfs. The online appendix provides a collation of MKO-system YJHKL'M' and IRAC photometry for a sample of M, L, and T dwarfs. There are 12 dwarfs currently known with H-[4.5]>3.0, and 500K<~T_eff_<~800K, which we examine in detail. The ages of the dwarfs in the sample range from very young (0.1-1.0Gyr) to relatively old (3-12Gyr). The mass range is possibly as low as 5 Jupiter masses to up to 70 Jupiter masses, i.e., near the hydrogen burning limit. The metallicities also span a large range, from [m/H]=-0.3 to [m/H]=+0.3.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/1585
- Title:
- Mn abundances of Galactic disc stars
- Short Name:
- J/MNRAS/454/1585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present and discuss the observations of the Mn abundances for 247 FGK dwarfs, located in the Galactic disc with metallicity -1<[Fe/H]<+0.3. The observed stars belong to the substructures of the Galaxy thick and thin disks, and to the Hercules stream. The observations were conducted using the 1.93m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle-type spectrographs ELODIE and SOPHIE. The abundances were derived under the LTE approximation, with an average error for the [Mn/Fe] ratio of 0.10dex. For most of the stars in the sample, Mn abundances are not available in the literature. We obtain an evolution of [Mn/Fe] ratio with the metallicity [Fe/H] consistent with previous data compilations. In particular, within the metallicity range covered by our stellar sample, the [Mn/Fe] ratio is increasing with the increase of metallicity. This due to the contribution to the Galactic chemical evolution of Mn and Fe from thermonuclear supernovae. We confirm the baseline scenario where most of the Mn in the Galactic disc and in the Sun is made by thermonuclear supernovae. In particular, the effective contribution from core-collapse supernovae to the Mn in the Solar system is about 10-20 per cent. However, present uncertainties affecting the production of Mn and Fe in thermonuclear supernovae are limiting the constraining power of the observed [Mn/Fe] trend in the Galactic discs on, e.g. the frequency of different thermonuclear supernovae populations. The different production of these two elements in different types of thermonuclear supernovae needs to be disentangled by the dependence of their relative production on the metallicity of the supernova progenitor.
- ID:
- ivo://CDS.VizieR/J/A+A/285/247
- Title:
- Molecules in O- and C-rich envelopes
- Short Name:
- J/A+A/285/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of 10 microwave transitions of the molecules SiO, HCN, HNC, SiS, HC_3_N, CS, SO, and ^13^CO are presented in a total sample of 47 evolved stars. The studied sources are mainly O- and C-rich standard AGB stars, as well as O-rich red supergiants, S-type stars, protoplanetary nebulae and detached envelopes. We also take into account observations of these transitions, as well as of ^12^CO J=1-0, from the literature. The observations were carried out during May and September 1991 and June 1992 with the IRAM 30-m radiotelescope at Pico de Veleta (Spain); the resolution is 1MHz for 3mm data (100GHz) and 2 MHz for 2 and 1mm data (150 to 300GHz).
