- ID:
- ivo://CDS.VizieR/J/other/ApSS/364.172
- Title:
- 504 F-G dwarfs photometric metallicities
- Short Name:
- J/other/ApSS/364
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study, photometric metallicity and absolute magnitude calibrations were derived using F-G spectral type main-sequence stars in the Solar neighbourhood with precise spectroscopic, photometric and Gaia astrometric data for UBV photometry. The sample consists of 504 main-sequence stars covering the temperature, surface gravity and colour index intervals 5300<Teff<7300K, logg>4 (cgs) and 0.3<(B-V)0<0.8mag, respectively. Stars with relative trigonometric parallax errors {sigma}_{pi}/{pi}<=0.01 were preferred from Gaia DR2 data for the estimation of their M_V absolute magnitudes. In order to obtain calibrations, (U-B)0 and (B-V)0 colour indices of stars were preferred and a multi-variable second order equation was used. Calibrations are valid for main-sequence stars in the metallicity and absolute magnitude ranges -2<[Fe/H]<0.5dex and 2.5<M_V_<6mag, respectively. The mean value and standard deviation of the differences between original and estimated values for the metal abundance and absolute magnitude are <{Delta}[Fe/H]>=0.00+/-0.11dex and <{Delta}M_V_>=0.00+/-0.22mag, respectively. In this work, it has been shown that more precise iron abundance and absolute magnitude values were obtained with the new calibrations, compared to previous calibrations in the literature.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/456/1221
- Title:
- FGK dwarfs atmospheric parameters
- Short Name:
- J/MNRAS/456/1221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed extensive tests of the accuracy of atmospheric parameter determination for FGK stars based on the spectrum fitting procedure Spectroscopy Made Easy (sme). Our stellar sample consists of 13 objects, including the Sun, in the temperature range 5000-6600K and metallicity range -1.4-/+0.4. The analysed stars have the advantage of having parameters derived by interferometry. For each star, we use spectra obtained with different spectrographs and different signal-to-noise ratios (S/N). For the fitting, we adopted three different sets of constraints and test how the derived parameters depend upon the spectral regions (masks) used in sme. We developed and implemented in sme a new method for estimating uncertainties in the resulting parameters based on fitting residuals, partial derivatives, and data uncertainties. For stars in the 5700-6600K range, the best agreement with the effective temperatures derived by interferometry is achieved when spectrum fitting includes the H{alpha} and H{beta} lines, while for cooler stars the choice of the mask does not affect the results. The derived atmospheric parameters do not strongly depend on spectral resolution and S/N of the observations, while the uncertainties in temperature and surface gravity increase with increasing effective temperature, with minima at 50K in Teff and 0.1dex in logg, for spectra with S/N=150-200. A non-local thermodynamic equilibrium (NLTE) analysis of the TiI/TiII and FeI/FeII ionization equilibria and abundances determined from the atomic CI (NLTE) and molecular CH species supports the parameters we derived with sme by fitting the observed spectra including the hydrogen lines.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/9
- Title:
- FGK stars magnetic activity in LAMOST-Kepler field
- Short Name:
- J/ApJS/247/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and R_HK_^+^, for 59816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with logR_HK_^+^. We estimate the power-law indexes between Reff and R_HK_^+^ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca ii H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A85
- Title:
- 3748 FGK stars spectroscopic parameters
- Short Name:
- J/A+A/636/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has observed the H-band spectra of over 200000 stars with R~22 000. The main motivation for this work is to test an alternative method to the standard APOGEE pipeline (APOGEE Stellar Parameter and Chemical Abundances Pipeline, ASPCAP) to derive parameters in the near-infrared (NIR) for FGK dwarfs. iSpec and Turbospectrum are used to generate synthetic spectra matching APOGEE observations and to determine the parameters through chi^2^ minimization. We present spectroscopic parameters (Teff, [M/H], logg, v_mic_) for a sample of 3748 main-sequence and subgiant FGK stars, obtained from their APOGEE H-band spectra. We compare our output parameters with the ones obtained with ASPCAP for the same stellar spectrum, and find that the values agree within the expected uncertainties. A comparison with the optical samples, California Planet Survey, HARPS-GTO, and PASTEL is also available, and median differences below 10K for Teff and 0.2dex for [M/H] are found. Reasons for these differences are explored. The full H-band line list, the line selection for the synthesis, and the synthesized spectra are available for download, as are the calculated parameters and their estimated uncertainties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2749
- Title:
- 257 field giant stars spectroscopic parameters
- Short Name:
- J/MNRAS/448/2749
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of stellar parameters of planet-hosting stars, such as metallicity and chemical abundances, help us to understand the theory of planet formation and stellar evolution. Here, we present a catalogue of accurate stellar atmospheric parameters and iron abundances for a sample of 257 K and G field evolved stars that are being surveyed for planets using precise radial-velocity measurements as part of the Coralie programme to search for planets around giants. The analysis was done using a set of high-resolution and high-signal-to-noise Ultraviolet and Visible Echelle Spectrograph spectra. The stellar parameters were derived using Fe I and II ionization and excitation equilibrium methods. To take into account possible effects related to the choice of the lines on the derived parameters, we used three different iron line-list sets in our analysis, and the results differ among themselves by a small factor for most of stars. For those stars with previous literature parameter estimates, we found very good agreement with our own values. In the present catalogue, we are providing new precise spectroscopic measurements of effective temperature, surface gravity, microturbulence, and metallicity for 190 stars for which it has not been found or published in previous articles.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/175
- Title:
- First release of the MaNGA Stellar Library (MaStar)
- Short Name:
- J/ApJ/883/175
- Date:
- 29 Nov 2021 07:46:33
- Publisher:
- CDS
- Description:
- We present the first release of the MaNGA Stellar Library (MaStar), which is a large, well-calibrated, high-quality empirical library covering the wavelength range 3622-10354{AA} at a resolving power of R~1800. The spectra were obtained using the same instrument as used by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, by piggybacking on the Sloan Digital Sky Survey (SDSS-IV)/Apache Point Observatory Galaxy Evolution Experiment 2-N (APOGEE-2N) observations. Compared to previous empirical libraries, the MaStar library will have a higher number of stars and a more comprehensive stellar-parameter coverage, especially of cool dwarfs, low-metallicity stars, and stars with different [{alpha}/Fe], achieved by a sophisticated target-selection strategy that takes advantage of stellar-parameter catalogs from the literature. This empirical library will provide a new basis for stellar-population synthesis and is particularly well suited for stellar-population analysis of MaNGA galaxies. The first version of the library contains 8646 high-quality per-visit spectra for 3321 unique stars. Compared to photometry, the relative flux calibration of the library is accurate to 3.9% in g-r, 2.7% in r-i, and 2.2% in i-z. The data are released as part of SDSS Data Release 15. We expect the final release of the library to contain more than 10000 stars.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A44
- Title:
- FLAMES observations of NGC6535
- Short Name:
- J/A+A/607/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand globular clusters (GCs) we need to comprehend how their formation process was able to produce their abundance distribution of light elements. In particular, we need to figure out which stars imprinted the peculiar chemical signature of GCs. One of the best way is to study the light-element anti-correlations in a large sample of GCs, analysed homogeneously. As part of our spectroscopic survey of GCs with FLAMES, we present here the results of our study of about 30 red giant member stars in the low-mass, low-metallicity Milky Way cluster NGC 6535. We measured its metallicity (finding [Fe/H]=-1.95, rms=0.04dex in our homogeneous scale) and other elements, in particular we concentrate here on O and Na abundances. These elements define the normal Na-O anti-correlation of classical GCs, making NGC 6535 perhaps the lowest mass cluster with confirmed presence of multiple populations. We updated the census of Galactic and extragalactic GCs for which a statement on the presence or absence of multiple populations can be made on the basis of high-resolution spectroscopy preferentially, or photometry and low-resolution spectroscopy otherwise, discussing the importance of mass and age of the clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/696/729
- Title:
- Fluxes and abundances of PNe in M33
- Short Name:
- J/ApJ/696/729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The planetary nebula (PN) population of M33 is studied via multifiber spectroscopy with Hectospec at the MMT. In this paper, we present the spectra of 102 PNe, whereas plasma diagnostic and chemical abundances were performed on the 93 PNe where the necessary diagnostic lines were measured. About 20% of the PNe are compatible with being Type I; the rest of the sample is the progeny of an old disk stellar population, with main sequence masses M<3M_{sun}_ and ages t>0.3Gyr. Our observations do not seem to imply that the metallicity gradient across the M33 disk has flattened considerably with time. We report also the discovery of a PN with Wolf-Rayet features, PN039, belonging the class of late [WC] stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/553
- Title:
- Fluxes in nearby star-forming galaxies
- Short Name:
- J/ApJ/706/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Compared to starburst galaxies, normal star-forming galaxies have been shown to display a much larger dispersion of the dust attenuation at fixed reddening through studies of the IRX-{beta} diagram (the IR/UV ratio "IRX" versus the UV color "{beta}"). To investigate the causes of this larger dispersion and attempt to isolate second parameters, we have used GALEX UV, ground-based optical, and Spitzer infrared imaging of eight nearby galaxies, and examined the properties of individual UV and 24um selected star-forming regions. We concentrated on star-forming regions, in order to isolate simpler star formation histories than those that characterize whole galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A12
- Title:
- Foreground Galactic stars properties
- Short Name:
- J/A+A/555/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the chemical and kinematic properties of roughly a thousand FLAMES-GIRAFFE LR8 spectra of faint magnitude foreground Galactic stars observed serendipitously during extra-galactic surveys in four lines-of-sight: three in the southern Galactic hemisphere (surveys of the Carina, Fornax and Sculptor dwarf spheroidal galaxies) and one in the northern Galactic hemisphere (a survey of the Sextans dwarf spheroidal galaxy). The foreground stars span distances up to ~3kpc from the Galactic plane and Galactocentric radii up to 11kpc. The stellar atmospheric parameters (effective temperature, surface gravity, metallicity) are obtained by an automated parameterisation pipeline and the distances of the stars are then derived by a projection of the atmospheric parameters on a set of theoretical isochrones using a Bayesian approach. The metallicity gradients are estimated for each line-of-sight and compared with predictions from the Besancon model of the Galaxy, in order to test the chemical structure of the thick disc. Finally, we use the radial velocities in each line-of-sight to derive a proxy for either the azimuthal or the vertical component of the orbital velocity of the stars. Only three lines-of-sight have a sufficient number of foreground stars for a robust analysis. Towards Sextans in the Northern Galactic hemisphere and Sculptor in the South, we measure a consistent decrease in mean metallicity with height from the Galactic plane, suggesting a chemically symmetric thick disc. This decrease can either be due to an intrinsic thick disc metallicity gradient, or simply due to a change in the thin disc/thick disc population ratio and no intrinsic metallicity gradients for the thick disc. We favour the latter explanation. In contrast, we find evidence of an unpredicted metal-poor population in the direction of Carina. This population was earlier detected by Wyse et al. (2006ApJ...639L..13W), but our more detailed analysis provides robust estimates of its location (|Z|<1kpc), metallicity (-2<[M/H]<-1dex) and azimuthal orbital velocity (V_phi_~120km/s).
