- 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).
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/154/259
- Title:
- Fundamental parameters of Tycho-2 & TGAS stars
- Short Name:
- J/AJ/154/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present bolometric fluxes and angular diameters for over 1.6 million stars in the Tycho-2 catalog (I/259), determined using previously determined empirical color-temperature and color-flux relations. We vet these relations via full fits to the full broadband spectral energy distributions for a subset of benchmark stars and perform quality checks against the large set of stars for which spectroscopically determined parameters are available from LAMOST, RAVE, and/or APOGEE. We then estimate radii for the 355502 Tycho-2 stars in our sample whose Gaia DR1 (I/337) parallaxes are precise to ~<10%. For these stars, we achieve effective temperature, bolometric flux, and angular diameter uncertainties of the order of 1%-2% and radius uncertainties of order 8%, and we explore the effect that imposing spectroscopic effective temperature priors has on these uncertainties. These stellar parameters are shown to be reliable for stars with T_eff_~<7000 K. The over half a million bolometric fluxes and angular diameters presented here will serve as an immediate trove of empirical stellar radii with the Gaia second data release, at which point effective temperature uncertainties will dominate the radius uncertainties. Already, dwarf, subgiant, and giant populations are readily identifiable in our purely empirical luminosity-effective temperature (theoretical) Hertzsprung-Russell diagrams.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/36
- Title:
- Ga, Ge, As, Kr, Cd, Sn and Pb column densities
- Short Name:
- J/ApJS/236/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an extensive analysis of the gas-phase abundances and depletion behaviors of neutron-capture elements in the interstellar medium (ISM). Column densities (or upper limits to the column densities) of Ga II, Ge II, As II, Kr I, Cd II, Sn II, and Pb II are determined for a sample of 69 sight lines with high- and/or medium-resolution archival spectra obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope. An additional 59 sight lines with column density measurements reported in the literature are included in our analysis. Parameters that characterize the depletion trends of the elements are derived according to the methodology developed by Jenkins (2009, J/ApJ/700/1299). The depletion patterns exhibited by Ga and Ge comport with expectations based on the depletion results obtained for many other elements. Arsenic exhibits much less depletion than expected, and its abundance in low-depletion sight lines may even be supersolar. We confirm a previous finding by Jenkins that the depletion of Kr increases as the overall depletion level increases from one sight line to another. Cadmium shows no such evidence of increasing depletion. We find a significant amount of scatter in the gas-phase abundances of Sn and Pb. For Sn, at least, the scatter may be evidence of real intrinsic abundance variations due to s-process enrichment combined with inefficient mixing in the ISM.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/138
- Title:
- Gaia and LAMOST DR4 M giant members of Sgr stream
- Short Name:
- J/ApJ/874/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use LAMOST DR4 M giants combined with Gaia DR2 proper motions and ALLWISE photometry to obtain an extremely pure sample of Sagittarius (Sgr) stream stars. Using TiO5 and CaH spectral indices as indicators, we selected a large sample of M-giant stars from M-dwarf stars in LAMOST DR4 spectra. Considering the position, distance, proper motion, and angular momentum distribution, we obtained 164 pure Sgr stream stars. We find that the trailing arm has higher energy than the leading arm in the same angular momentum. The trailing arm we detected extends to a heliocentric distance of ~130kpc at {Lambda}_{sun}_~170{deg}, which is consistent with the feature found in RR Lyrae in Sesar+ (2017, J/ApJ/844/L4). Both of these detections of Sgr, in M-giants and in RR Lyrae, imply that the Sgr stream may contain multiple stellar populations with a broad metallicity range.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A6
- Title:
- Gaia Catalogue of Nearby Stars - GCNS
- Short Name:
- J/A+A/649/A6
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We produce a clean and well-characterised catalogue of objects within 100 pc of the Sun from the Gaia Early Data Release 3. We characterise the catalogue through comparisons to the full data release, external catalogues, and simulations. We carry out a first analysis of the science that is possible with this sample to demonstrate its potential and best practices for its use. The selection of objects within 100 pc from the full catalogue used selected training sets, machine-learning procedures, astrometric quantities, and solution quality indicators to determine a probability that the astrometric solution is reliable. The training set construction exploited the astrometric data, quality flags, and external photometry. For all candidates we calculated distance posterior probability densities using Bayesian procedures and mock catalogues to define priors. Any object with reliable astrometry and a non-zero probability of being within 100pc is included in the catalogue. We have produced a catalogue of 331312 objects that we estimate contains at least 92% of stars of stellar type M9 within 100pc of the Sun. We estimate that 9% of the stars in this catalogue probably lie outside 100pc, but when the distance probability function is used, a correct treatment of this contamination is possible. We produced luminosity functions with a high signal-to-noise ratio for the main-sequence stars, giants, and white dwarfs. We examined in detail the Hyades cluster, the white dwarf population, and wide-binary systems and produced candidate lists for all three samples. We detected local manifestations of several streams, superclusters, and halo objects, in which we identified 12 members of Gaia Enceladus. We present the first direct parallaxes of five objects in multiple systems within 10pc of the Sun. We provide the community with a large, well-characterised catalogue of objects in the solar neighbourhood. This is a primary benchmark for measuring and understanding fundamental parameters and descriptive functions in astronomy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/2771
- Title:
- Gaia-DR2 distance to the W3 Complex
- Short Name:
- J/MNRAS/487/2771
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Perseus Arm is the closest Galactic spiral arm from the Sun, offering an excellent opportunity to study in detail its stellar population. However, its distance has been controversial with discrepancies by a factor of two. Kinematic distances are in the range 3.9-4.2kpc as compared to 1.9-2.3kpc from spectrophotometric and trigonometric parallaxes, reinforcing previous claims that this arm exhibits peculiar velocities. We used the astrometric information of a sample of 31 OB stars from the star-forming W3Complex to identify another 37 W3 members and to derive its distance from their Gaia-DR2 parallaxes with improved accuracy. The Gaia-DR2 distance to the W3Complex, 2.14^+0.08^_-0.07_kpc, coincides with the previous stellar distances of ~2kpc. The Gaia-DR2 parallaxes tentatively show differential distances for different parts of the W3 Complex: W3 Main, located to the NE direction, is at 2.30^+0.19^_-0.16_kpc, the W3 Cluster (IC1795), in the central region of the complex, is at 2.17^+0.12^_-0.11_kpc, and W3(OH) is at 2.00^+0.29^_-0.23_kpc to the SW direction. The W3 Cluster is the oldest region, indicating that it triggered the formation of the other two star-forming regions located at the edges of an expanding shell around the cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/2849
- Title:
- Gaia DR1 mass-radius relation of white dwarfs
- Short Name:
- J/MNRAS/465/2849
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Gaia Data Release 1 (DR1) sample of white dwarf parallaxes is presented, including six directly observed degenerates and 46 white dwarfs in wide binaries. This data set is combined with spectroscopic atmospheric parameters to study the white dwarf mass-radius relationship (MRR). Gaia parallaxes and G magnitudes are used to derive model atmosphere-dependent white dwarf radii, which can then be compared to the predictions of a theoretical MRR. We find a good agreement between Gaia DR1 parallaxes, published effective temperatures (T_eff_) and surface gravities (logg), and theoretical MRRs. As it was the case for Hipparcos, the precision of the data does not allow for the characterization of hydrogen envelope masses. The uncertainties on the spectroscopic atmospheric parameters are found to dominate the error budget and current error estimates for well-known and bright white dwarfs may be slightly optimistic. With the much larger Gaia DR2 white dwarf sample, it will be possible to explore the MRR over a much wider range of mass, T_eff_, and spectral types.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A128
- Title:
- Gaia DR2 study of Herbig Ae/Be stars
- Short Name:
- J/A+A/620/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Gaia Data Release 2 (DR2, Cat. I/345) to place 252 Herbig Ae/Be stars in the HR diagram and investigate their characteristics and properties. For all known Herbig Ae/Be stars with parallaxes in Gaia DR2, we collected their atmospheric parameters and photometric and extinction values from the literature. To these data we added near- and mid-infrared photometry, collected Halpha emission line properties such as equivalent widths and line profiles, and their binarity status. In addition, we developed a photometric variability indicator from Gaia's DR2 information. We provide masses, ages, luminosities, distances, photometric variabilities and infrared excesses homogeneously derived for the most complete sample of Herbig Ae/Be stars to date. We find that high mass stars have a much smaller infrared excess and have much lower optical variabilities compared to lower mass stars, with the break at around 7M_{sun}_. Halpha emission is generally correlated with infrared excess, with the correlation being stronger for infrared emission at wavelengths tracing the hot dust closest to the star. The variability indicator as developed by us shows that approximately 25% of all Herbig Ae/Be stars are strongly variable. We observe that the strongly variable objects display doubly peaked Halpha line profiles, indicating an edge-on disk. The fraction of strongly variable Herbig Ae stars is close to that found for A-type UX Ori stars. It had been suggested that this variability is in most cases due to asymmetric dusty disk structures seen edge-on. The observation here is in strong support of this hypothesis. Finally, the difference in dust properties occurs at 7M_{sun}_, while various properties traced at UV/optical wavelengths differ at a lower mass, 3M_{sun}_. The latter has been linked to different accretion mechanisms at work whereas the differing infrared properties and photometric variabilities are related to different or differently acting (dust-)disk dispersal mechanisms.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A70
- Title:
- Galactic and Magellanic Cloud Cepheids distance
- Short Name:
- J/A+A/550/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The metallicity dependence of the Cepheid period-luminosity (PL) relation is of importance in establishing the extragalactic distance scale. The aim of this paper is to investigate the metallicity dependence of the PL relation in V and K, based on a sample of 128 Galactic, 36 Large Magellanic Cloud (LMC), and 6 Small Magellanic Cloud (SMC) Cepheids with individual Baade-Wesselink (BW) distances (some of the stars also have an Hubble Space Telescope (HST) based and Hipparcos parallax or are in clusters) and individually determined metallicities from high-resolution spectroscopy. Literature values of the V-band, K-band, and radial velocity data were collected for the sample of Cepheids. Based on a (V-K) surface-brightness relation and a projection factor, distances were derived from a BW analysis. Since 2008, additional radial velocity data has been obtained using the 1.2m Euler telescope located at the La Silla observatory (see Groenewegen 2008A&A...488...25G for a description of the data taking and data reduction). The new Radial Velocity (RV) data are presented in Table 3.
- ID:
- ivo://CDS.VizieR/J/other/NewA/34.234
- Title:
- Galactic cataclysmic variables distances
- Short Name:
- J/other/NewA/34.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to determine the spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs), a J-band magnitude limited sample of 263 CVs has been established using a newly constructed period-luminosity-colours (PLCs) relation which includes J,KsJ,Ks and W1W1-band magnitudes in 2MASS and WISE photometries, and the orbital periods of the systems. This CV sample is assumed to be homogeneous regarding to distances as the new PLCs relation is calibrated with new or re-measured trigonometric parallaxes.
