- ID:
- ivo://CDS.VizieR/J/AJ/140/1911
- Title:
- Astrometric Grid Giant Star Survey. III.
- Short Name:
- J/AJ/140/1911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of high-resolution (~55000) spectral observations of 830 photometrically pre-selected candidate red giants in the magnitude range of V=9-12. We develop a pipeline for automated determination of the stellar atmospheric parameters from these spectra and estimate Teff, logg, [Fe/H], microturbulence velocity, and projected rotational velocities, vsin i, for the stars. The analysis confirms that the candidate selection procedure yielded red giants with very high success rate. We show that most of these stars are G and K giants with slightly subsolar metallicity ([Fe/H]~-0.3dex). An analysis of Mg abundances in the sample results in consistency of the [Mg/Fe] vs [Fe/H] trend with published results.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/PAZh/38/571
- Title:
- Astrophysical parameters for 593 open clusters
- Short Name:
- J/PAZh/38/571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on published data, we have compiled a catalogue of fundamental astrophysical parameters for 593 open clusters of the Galaxy. In particular, the catalogue provides the Galactic orbital elements for 500 clusters, the masses, central concentrations, and ellipticities for 424 clusters, the metallicities for 264 clusters, and the relative magnesium abundances for 56 clusters. We describe the sources of initial data and estimate the errors in the investigated parameters. The selection effects are discussed. The chemical and kinematical properties of the open clusters and field thin-disk stars are shown to differ. We provide evidence for the heterogeneity of the population of open star clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1567
- Title:
- Asymmetric thick disk. II. Kinematics
- Short Name:
- J/AJ/127/1567
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a kinematic signature associated with the observed asymmetry in the distribution of thick-disk/inner halo stars interior to the solar circle described in Paper I (Parker et al., 2003AJ....126.1346P). In that paper, we found a statistically significant excess (20%-25%) of stars in quadrant I (l~20{deg}-55{deg}) both above and below the plane (b~+/-25{deg} to b~+/-45{deg}) compared with the complementary region in quadrant IV. We have measured Doppler velocities for 741 stars, selected according to the same magnitude and color criteria, in the direction of the asymmetry and in the corresponding fields in quadrant IV. We have also determined spectral types and metallicities measured from the same spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A134
- Title:
- ATHOS. Flux ratio based stellar parameterization
- Short Name:
- J/A+A/619/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapidly increasing number of stellar spectra obtained by existing and future large-scale spectroscopic surveys feeds a demand for fast and efficient tools for the spectroscopic determination of fundamental stellar parameters. Such tools should not only comprise customized solutions for one particular survey or instrument, but, in order to enable cross-survey comparability, they should also be capable of dealing with spectra from a variety of spectrographs, resolutions, and wavelength coverages. To meet these ambitious specifications, we developed ATHOS (A Tool for HOmogenizing Stellar parameters), a fundamentally new analysis tool that adopts easy-to-use, computationally inexpensive analytical relations tying flux ratios (FRs) of designated wavelength regions in optical spectra to the stellar parameters effective temperature (Teff), iron abundance ([Fe/H]), and surface gravity (logg). Our Teff estimator is based on FRs from nine pairs of wavelength ranges around the Balmer lines H{beta} and H{alpha}, while for [Fe/H] and logg we provide 31 and 11 FRs, respectively, which are spread between ~4800{AA} and ~6500{AA}; a region covered by most optical surveys. The analytical relations employing these FRs were trained on N=124 real spectra of a stellar benchmark sample that covers a large parameter space of Teff~=4000 to 6500K (spectral types F to K), [Fe/H]~=-4.5 to 0.3dex, and logg~=1 to 5dex, which at the same time reflects ATHOS' range of applicability. We find accuracies of 97K for Teff, 0.16dex for [Fe/H], and 0.26dex for logg, which are merely bounded by finite uncertainties in the training sample parameters. ATHOS' internal precisions can be better by up to 70%. We tested ATHOS on six independent large surveys spanning a wide range of resolutions (R~=2000 to 52000), amongst which are the Gaia-ESO and the SDSS/SEGUE surveys. The exceptionally low execution time (<30ms per spectrum per CPU core) together with a comparison to the literature parameters showed that ATHOS can successfully achieve its main objectives, in other words fast stellar parametrization with cross-survey validity, high accuracy, and high precision. These are key to homogenize the output from future surveys, such as 4MOST or WEAVE.
- ID:
- ivo://CDS.VizieR/J/other/RAA/11.924
- Title:
- Atmospheric parameters for 771 stars
- Short Name:
- J/other/RAA/11.9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A number of spectroscopic surveys have been carried out or are planned to study the origin of the Milky Way. Their exploitation requires reliable automated methods and softwares to measure the fundamental parameters of the stars. Adopting the ULySS package, we have tested the effect of different resolutions and signal-to-noise ratios (SNR) on the measurement of the stellar atmospheric parameters (effective temperature Teff, surface gravity logg, and metallicity [Fe/H]). We show that ULySS is reliable to determine these parameters with medium-resolution spectra (R~2000). Then, we applied the method to measure the parameters of 771 stars selected in the commissioning database of the Guoshoujing Telescope (GSJT). The results were compared with the SDSS/SEGUE Stellar Parameter Pipeline (SSPP), and we derived precisions of 167K, 0.34dex, and 0.16dex for Teff, logg and [Fe/H] respectively. Furthermore, 120 of these stars are selected to construct the primary stellar spectra template library (Version 1.0) of GSJT, and will be deployed as basic ingredients for the GSJT automated parametrization pipeline.
- ID:
- ivo://CDS.VizieR/J/A+A/525/A71
- Title:
- Atmospheric parameters for 1273 stars
- Short Name:
- J/A+A/525/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Empirical libraries of stellar spectra play an important role in different fields. For example, they are used as reference for the automatic determination of atmospheric parameters, or for building synthetic stellar populations to study galaxies. The CFLIB (Coude-feed library, Indo-US) database is at present one of the most complete libraries, in terms of its coverage of the atmospheric parameters space (Teff, logg and [Fe/H]) and wavelength coverage 3460-9464{AA} at a resolution of ~1{AA} FWHM. Although the atmospheric parameters of most of the stars were determined from detailed analyses of high-resolution spectra, for nearly 300 of the 1273 stars of the library at least one of the three parameters is missing. For the others, the measurements, compiled from the literature, are inhomogeneous. In this paper, we re-determine the atmospheric parameters, directly using the CFLIB spectra, and compare them to the previous studies. Methods. We use the ULySS program to derive the atmospheric parameters, using the ELODIE library as a reference. Based on comparisons with several previous studies we conclude that our determinations are unbiased. For the 958 F,G, and K type stars the precision on Teff, logg, and [Fe/H] is respectively 43K, 0.13dex and 0.05dex. For the 53 M stars they are 82K, 0.22dex and 0.28dex. And for the 260 OBA type stars the relative precision on Teff is 5.1%, and on logg, and [Fe/H] the precision is respectively 0.19 dex and 0.16 dex. These parameters will be used to re-calibrate the CFLIB fluxes and to produce synthetic spectra of stellar populations.
- ID:
- ivo://CDS.VizieR/J/AJ/147/25
- Title:
- Atmospheric parameters of M4 stars
- Short Name:
- J/AJ/147/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new metallicities for stars of Galactic globular cluster M4 using the largest number of stars ever observed at high spectral resolution in any cluster. We analyzed 7250 spectra for 2771 cluster stars gathered with the Very Large Telescope (VLT) FLAMES+GIRAFFE spectrograph at VLT. These medium-resolution spectra cover a small wavelength range, and often have very low signal-to-noise ratios. We approached this data set by reconsidering the whole method of abundance analysis of large stellar samples from beginning to end. We developed a new algorithm that automatically determines the atmospheric parameters of a star. Nearly all of the data preparation steps for spectroscopic analyses are processed on the syntheses, not the observed spectra. For 322 red giant branch (RGB) stars with V<=14.7, we obtain a nearly constant metallicity, <[Fe/H]>=-1.07 ({sigma}=0.02). No difference in the metallicity at the level of 0.01 dex is observed between the two RGB sequences identified by Monelli et al. (2013MNRAS.431.2126M). For 1869 subgiant and main-sequence stars with V>14.7, we obtain <[Fe/H]>=-1.16 ({sigma}=0.09) after fixing the microturbulent velocity. These values are consistent with previous studies that have performed detailed analyses of brighter RGB stars at higher spectroscopic resolution and wavelength coverage. It is not clear if the small mean metallicity difference between brighter and fainter M4 members is real or is the result of the low signal-to-noise characteristics of the fainter stars. The strength of our approach is shown by recovering a metallicity close to a single value for more than 2000 stars, using a data set that is non-optimal for atmospheric analyses. This technique is particularly suitable for noisy data taken in difficult observing conditions.
- ID:
- ivo://CDS.VizieR/J/A+A/536/A71
- Title:
- Atmospheric parameters of nearby giant stars
- Short Name:
- J/A+A/536/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are conducting a precision radial velocity study of a sample of 164 nearby giant stars in the southern hemisphere. In this work we present the spectroscopic atmospheric parameters (Teff, logg , vmic and [Fe/H]) for all of our targets. By comparing the position on the HR diagram with stellar evolutionary tracks, we derived the mass, radius and evolutionary status for every star in our sample. In addition, rotational velocities are also measured.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A143
- Title:
- Atmospheric parameters of stars for UV models
- Short Name:
- J/A+A/538/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectral predictions of stellar population models are not as accurate in the ultra-violet (UV) as in the optical wavelength domain. One of the reasons is the lack of high-quality stellar libraries. The New Generation Stellar Library (NGSL), recently released, represents a significant step towards the improvement of this situation. To prepare NGSL for population synthesis, we determined the atmospheric parameters of its stars, we assessed the precision of the wavelength calibration and characterised its intrinsic resolution. We also measured the Galactic extinction for each of the NGSL stars. For our analyses we used ULySS, a full spectrum fitting package, fitting the NGSL spectra against the MILES interpolator. We find that the wavelength calibration is precise up to 0.1pix, after correcting a systematic effect in the optical range. The spectral resolution varies from 3{AA} in the UV to 10{AA} in the near-infrared (NIR), corresponding to a roughly constant reciprocal resolution R~1000 and an instrumental velocity dispersion 130km/s. We derived the atmospheric parameters homogeneously. The precision for the FGK stars is 42K, 0.24 and 0.09dex for Teff, logg and [Fe/H], respectively. The corresponding mean errors are 29K, 0.50 and 0.48dex for the M stars, and for the OBA stars they are 4.5 percent, 0.44 and 0.18dex. The comparison with the literature shows that our results are not biased.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/1422
- Title:
- Atmospheric param. of 169 FGKM stars
- Short Name:
- J/MNRAS/434/1422
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The asteroseismic and planetary studies, like all research related to stars, need precise and accurate stellar atmospheric parameters as input. We aim at deriving the effective temperature (Teff), the surface gravity (logg), the metallicity ([Fe/H]), the projected rotational velocity (vsini) and the MK type for 169 F-, G-, K- and M-type Kepler targets which were observed spectroscopically from the ground with five different instruments. We use two different spectroscopic methods to analyse 189 high-resolution, high-signal-to-noise spectra acquired for the 169 stars. For 67 stars, the spectroscopic atmospheric parameters are derived for the first time. KIC 9693187 and 11179629 are discovered to be double-lined spectroscopic binary systems. The results obtained for those stars for which independent determinations of the atmospheric parameters are available in the literature are used for a comparative analysis. As a result, we show that for solar-type stars the accuracy of present determinations of atmospheric parameters is +/-150K in Teff, +/-0.15dex in [Fe/H] and +/-0.3dex in logg. Finally, we confirm that the curve-of-growth analysis and the method of spectral synthesis yield systematically different atmospheric parameters when they are applied to stars hotter than 6000K.
