- ID:
- ivo://CDS.VizieR/J/ApJ/740/60
- Title:
- Equivalent widths for NGC2419 and NGC7099 RGB stars
- Short Name:
- J/ApJ/740/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/1960
- Title:
- ESPaDOnS spectropolarimeter obs. of M dwarfs
- Short Name:
- J/MNRAS/475/1960
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Present and future high-precision radial-velocity spectrometers dedicated to the discovery of low-mass planets orbiting low-mass dwarfs need to focus on the best selected stars to make an efficient use of telescope time. In the framework of the preparation of the SPIRou Input Catalogue (SPIC), the CoolSnap program aims at screening M dwarfs in the solar neighbourhood against binarity, rapid rotation, activity, etc. To optimize the selection, this paper describes the methods used to compute effective temperature, metallicity, projected rotation velocity of a large sample of 440 M dwarfs observed in the visible with the high-resolution spectropolarimeter Echelle SpectroPolArimetric Device for the ObservatioN of Stars (ESPaDOnS) at Canada-France-Hawaii Telescope. It also summarizes known and newly discovered spectroscopic binaries, and stars known to belong to visual multiple systems. A calibration of the projected rotation velocity versus measured line widths for M dwarfs observed by the ESPaDOnS spectropolarimeter is derived, and the resulting values are compared to equatorial rotation velocities deduced from rotation periods and radii. A comparison of the derived effective temperatures and metallicities with literature values is also conducted. Finally, the radial-velocity uncertainty of each star in the sample is estimated, to narrow down the selection of stars to be included into the SPIC.
- ID:
- ivo://CDS.VizieR/J/AJ/117/981
- Title:
- Estimation of stellar metal abundance. II.
- Short Name:
- J/AJ/117/981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have recalibrated a method for the estimation of stellar metal abundance, parameterized as [Fe/H], based on medium-resolution (1-2{AA}) optical spectra (the majority of which cover the wavelength range 3700-4500{AA}). The equivalent width of the Ca II K line (3933{AA}) as a function of [Fe/H] and broadband B-V color, as predicted from spectrum synthesis and model atmosphere calculations, is compared with observations of 551 stars with high-resolution abundances available from the literature (a sevenfold increase in the number of calibration stars that were previously available). A second method, based on the Fourier autocorrelation function technique first described by Ratnatunga & Freeman (1989, Cat. <V/65>), is used to provide an independent estimate of [Fe/H], as calibrated by comparison with 405 standard-star abundances.
- ID:
- ivo://CDS.VizieR/J/ApJ/885/100
- Title:
- Evolu. star mass-metallicity relation. II.
- Short Name:
- J/ApJ/885/100
- Date:
- 16 Mar 2022 11:50:55
- Publisher:
- CDS
- Description:
- We present the stellar mass-[Fe/H] and mass-[Mg/H] relation of quiescent galaxies in two galaxy clusters at z~0.39 and z~0.54. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for z~0 Sloan Digital Sky Survey galaxies, we confirm our previous finding that the mass-[Fe/H] relation evolves with redshift. The mass-[Fe/H] relation at higher redshift has lower normalization and possibly steeper slope. However, based on our sample, the mass-[Mg/H] relation does not evolve over the observed redshift range. We use a simple analytic chemical evolution model to constrain the average outflow that these galaxies experience over their lifetime, via the calculation of mass-loading factor. We find that the average mass-loading factor {eta} is a power-law function of galaxy stellar mass, {eta}{prop}M*^-0.21{+/-}0.09^. The measured mass-loading factors are consistent with the results of other observational methods for outflow measurements and with the predictions where outflow is caused by star formation feedback in turbulent disks.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A70
- Title:
- Evolved planet hosts - stellar parameters
- Short Name:
- J/A+A/557/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is still being debated whether the well-known metallicity - giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Precise stellar parameters are also crucial to planetary research for several other reasons. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity - giant planet connection for evolved stars. A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (logg<3.0dex) with respect to red giants without planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/895/52
- Title:
- EW and chemical abundances in 211 stars with HARPS
- Short Name:
- J/ApJ/895/52
- Date:
- 15 Mar 2022 07:30:10
- Publisher:
- CDS
- Description:
- Magnetic fields and stellar spots can alter the equivalent widths of absorption lines in stellar spectra, varying during the activity cycle. This also influences the information that we derive through spectroscopic analysis. In this study, we analyze high-resolution spectra of 211 sunlike stars observed at different phases of their activity cycles, in order to investigate how stellar activity affects the spectroscopic determination of stellar parameters and chemical abundances. We observe that the equivalent widths of lines can increase as a function of the activity index log R_HK_' during the stellar cycle, which also produces an artificial growth of the stellar microturbulence and a decrease in effective temperature and metallicity. This effect is visible for stars with activity indexes log R_HK_'>=-5.0 (i.e., younger than 4-5Gyr), and it is more significant at higher activity levels. These results have fundamental implications on several topics in astrophysics that are discussed in the paper, including stellar nucleosynthesis, chemical tagging, the study of Galactic chemical evolution, chemically anomalous stars, the structure of the Milky Way disk, stellar formation rates, photoevaporation of circumstellar disks, and planet hunting.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A114
- Title:
- EW and [Fe/H] for 30000 globular cluster RGB stars
- Short Name:
- J/A+A/635/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CaII triplet in the near-infrared at 8498, 8542, and 8662{AA} is visible in stars with spectral types between F and M and can be used to determine their metallicities. We calibrated the relation using average cluster metallicities from literature and MUSE spectra, and extend it below the horizontal branch - a cutoff that has traditionally been made to avoid a non-linear relation - using a quadratic function. In addition to the classic relation based on V-\vhb$ we used calibrations based on absolute magnitude and luminosity and used it for those cluster, for which no HB brightness was available. The obtained relations are then used to calculate metallicities for all the stars in the sample.
- ID:
- ivo://CDS.VizieR/V/137D
- Title:
- Extended Hipparcos Compilation (XHIP)
- Short Name:
- V/137D
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Extended Hipparcos Compilation (XHIP) cross-references the New Hipparcos Reduction (HIP2, Cat. I/311) with relatable data from a broad survey of presently available sources. The resulting collection uniquely assigns 116,096 spectral classifications, 46,392 radial velocities, and 19,097 iron abundances [Fe/H] to Hipparcos stars. Stellar classifications from SIMBAD and indications of multiplicity from either CCDM (Cat. I/274) or WDS (Cat. B/wds) are provided. Parameters for solar encounters and Galactic orbits are calculated for a subset of stars that can be made kinematically complete. Memberships in open clusters and stellar associations are assigned. We also provide stellar ages from The Geneva-Copenhagen survey of the Solar neighbourhood III (Cat. V/130), identifications of exoplanet host stars, and supplemental photometry from 2MASS (Cat. II/246) and SIMBAD.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A134
- Title:
- Fe abundances for 28 XMM galaxy clusters
- Short Name:
- J/A+A/527/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundances of Fe in the intracluster medium of nearby (z<0.08) clusters were measured up to 0.3~0.5r_180_. We analyzed 28 clusters of galaxies observed with XMM-Newton. We derived Fe abundances from the flux ratios of Fe lines to the continuum within an energy range of 3.5-6keV to minimize and evaluate systematic uncertainties.
- ID:
- ivo://CDS.VizieR/J/A+A/522/A26
- Title:
- Fe Abundances in metal-poor stars
- Short Name:
- J/A+A/522/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The determination of Lithium abundance A(Li) is extremely sensitive to the adopted temperature scale, so that a Teff bias might mimic a trend in A(Li). We present here VLT-UVES Li abundances for 28 halo dwarf stars between [Fe/H]=-2.5 and -3.5, 10 of which have [Fe/H]<-3. Four different Teff scales have been used: Direct Infrared Flux Method (IRFM) has been used on the basis of 2MASS infrared photometry; H{alpha} wings have been fitted against two synthetic grids computed by means of 1D LTE atmosphere models, and a grid of H{alpha} profiles computed by means of 3D hydrodynamical atmosphere models. As a result, we confirm previous claims that A(Li) does not exhibit a plateau below [Fe/H]=-3. A strong positive correlation with [Fe/H] appears, not influenced by the choice of the Teff estimator. From a linear fit, we obtain a strong slope of about 0.30 dex in A(Li) per dex in [Fe/H], significant to 2-3, and consistent within 1 among all the four Teff estimators. A significant slope is also detected in the A(Li)-Teff plane, driven mainly by the coolest stars in the sample (Teff<6250), which appear Li-poor. However, removing such stars does not alter significantly the behavior in the A(Li)-[Fe/H] plane. When the full sample is considered, the scatter in A(Li) increases by a factor of 2 towards lower metallicities, while the plateau appears very thin above [Fe/H]=-2.8. At this metallicity, the plateau lies at A(Li)3D,NLTE=2.199+/-0.086.
