- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/639/A64
- Title:
- Extended Meingast 1 source catalogue
- Short Name:
- J/A+A/639/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nearby stellar streams carry unique information on the dynamical evolution and disruption of stellar systems in the Galaxy, the mass distribution in the disk, and they provide unique targets for planet formation and evolution studies. Recently, Meingast 1, a 120{deg} stellar stream with a length of at least 400pc, was discovered. We aim to revisit the Meingast 1 stream to search for new members within its currently known 400pc extent, using Gaia DR2 data and an innovative machine learning approach. We used a bagging classifier of one-class support vector machines with Gaia DR2 data to perform a 5D search (positions and proper motions) for new stream members. The ensemble was created by randomly sampling 2.4 million hyper-parameter realizations admitting classifiers that fulfill a set of prior assumptions. We used the variable prediction frequency resulting from the multitude of classifiers to estimate a stream membership criterion, which we used to select high-fidelity sources. We used the HR diagram and the Cartesian velocity distribution as test and validation tools. We find about 2000 stream members with high fidelity, or about an order of magnitude more than previously known, unveiling the stream's population across the entire stellar mass spectrum, from B stars to M stars, including white dwarfs. We find that, apart from being slightly more metal poor, the HRD of the stream is indistinguishable from that of the Pleiades cluster. For the mass range at which we are mostly complete, ~0.2M_{sun}_<M<~4M_{sun}_, we find a normal IMF, allowing us to estimate the total mass of stream to be about 2000M_{sun}_, making this relatively young stream by far the most massive one known. In addition, we identify several white dwarfs as potential stream members. The nearby Meingast 1 stream, due to its richness, age, and distance, is a new fundamental laboratory for star and planet formation and evolution studies for the poorly studied and gravitationally unbound star formation mode. We also demonstrate that one-class support vector machines can be effectively used to unveil the full stellar populations of nearby stellar systems with Gaia data.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/113
- Title:
- Extinction law in the Cep OB3b young cluster
- Short Name:
- J/ApJ/786/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K_s_ photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R_V_=3.1 and R_V_=5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A_V_ is investigated and we find the extinction law becomes shallower for regions with A_V_>2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/649/L8
- Title:
- Extreme adaptive optics astrometry of R136
- Short Name:
- J/A+A/649/L8
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We compared high-contrast near-infrared images of the core of R136 taken by VLT/SPHERE, in two epochs separated by 3.06 years. For the first time we monitored the dynamics of the detected sources in the core of R136 from a ground-based telescope with adaptive optics. The aim of these observations was to search for High prOper Motion cAndidates (HOMAs) in the central region of R136 (r<6") where it has been challenging for other instruments. Two bright sources (K<15mag and V<16mag) are located near R136a1 and R136c (massive WR stars) and have been identified as potential HOMAs. These sources have significantly shifted in the images with respect to the mean shift of all reliable detected sources and their neighbours, and six times their own astrometric errors. We calculate their proper motions to be 1.36+/-0.22mas/yr^2^ (321+/-52km/s) and 1.15+/-0.11mas/yr^2^ (273+/-26km/s). We discuss different possible scenarios to explain the magnitude of such extreme proper motions, and argue for the necessity to conduct future observations to conclude on the nature of HOMAs in the core of R136.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/1681
- Title:
- Extremely metal-poor stars CaII triplet
- Short Name:
- J/MNRAS/434/1681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extend our previous calibration of the infrared CaII triplet (CaT) as a metallicity indicator to the metal-poor regime by including observations of 55 field stars with [Fe/H] down to -4.0dex. While we previously solved the saturation at high metallicity using a combination of a Lorentzian and a Gaussian to reproduce the line profiles, in this paper we address the non-linearity at low metallicity following the suggestion of Starkenburg et al. of adding two non-linear terms to the relation among the [Fe/H], luminosity and strength of the calcium triplet lines. Our calibration thus extends from -4.0 to +0.5 in metallicity and is presented using four different luminosity indicators: V-V_HB_, M_V_, M_I_ and M_K_. The calibration obtained in this paper results in a tight correlation between [Fe/H] abundances measured from high-resolution spectra and [Fe/H] values derived from the CaT, over the whole metallicity range covered.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/13
- Title:
- Faint dwarfs in NGC 2547
- Short Name:
- J/MNRAS/358/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intermediate resolution spectroscopy from the European Southern Observatory Very Large Telescope is analysed for 63 photometrically selected low-mass (0.08-0.30M_{sun}_) candidates of the open cluster NGC 2547. We have confirmed membership for most of these stars using radial velocities, and found that lithium remains undepleted for cluster stars with I>17.54+/-0.14 and Ks>14.86+/-0.12. From these results, several pre-main-sequence evolutionary models give almost model independent ages of 34-36Myr, with a precision of 10%. These ages are only slightly larger than the ages of 25-35(+/-5)Myr obtained using the same models to fit isochrones to higher mass stars descending towards the zero-age main-sequence, both in empirically calibrated and theoretical colour-magnitude diagrams. This agreement between age determinations in different mass ranges is an excellent test of the current generation of low-mass pre-main-sequence stellar models and lends confidence to ages determined with either method between 30 and 120Myr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/465
- Title:
- Fast-rotating M dwarfs in NGC2516
- Short Name:
- J/MNRAS/407/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report radial velocities (RVs), projected equatorial velocities (vsini) and CaII triplet (CaT) chromospheric activity indices for 237 late-K to mid-M candidate members of the young open cluster NGC 2516. These stars have published rotation periods between 0.1 and 15d. Intermediate-resolution spectra were obtained using the Giraffe spectrograph at the Very Large Telescope. Membership was confirmed on the basis of their RVs for 210 targets.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A54
- Title:
- Fe, Mg, Ti in Galactic clusters
- Short Name:
- J/A+A/628/A54
- Date:
- 02 Nov 2021 11:16:10
- Publisher:
- CDS
- Description:
- We test the effects of non-local thermodynamic equilibrium (NLTE) on the spectra of FGK-type stars across a wide range of metallicity and to derive abundance of Fe, Mg, and Ti for a sample of Galactic star clusters. We extend the Payne fitting approach to draw on NLTE and LTE spectral models in order to determine stellar parameters and chemical abundances for the Gaia-ESO benchmark stars. We also analyse the medium-resolution Giraffe spectra of 742 stars in 13 open and globular clusters in the Milky Way galaxy. We show that this approach accurately recovers effective temperatures, surface gravities, and abundances of the benchmark stars and clusters members. The differences between NLTE and LTE stellar parameters are small for the metal-rich stars. However, for metal-poor stars [Fe/H]<-1, the NLTE estimates of Teff, log(g) and [Fe/H] are higher than LTE estimates, and the systematic offset increases with decreasing metallicity. Our LTE measurements of metallicities and abundances in the Galactic clusters are in a good agreement with the earlier literature studies. For the majority of these clusters, our study yields the first estimates of NLTE abundances of Fe, Mg and Ti. The NLTE [Fe/H] are systematically higher, whereas the average NLTE [Mg/Fe] abundance ratios are ~0.15dex lower, compared to LTE. All clusters investigated in this work appear homogeneous in Fe and Ti, with the intra-cluster abundance variations of less then 0.1dex. We confirm large dispersions of [Mg/Fe] ratios for NGC 2808, NGC 4833 and M 15. Our results shows that NLTE analysis change the mean abundance ratios in the clusters, but does not influence the intra-cluster abundance dispersions. Combining the Payne fitting approach with NLTE spectral models as input is a powerful tool for a detailed exploration of the large-scale spectroscopic stellar surveys.
- ID:
- ivo://CDS.VizieR/J/ApJS/85/315
- Title:
- F, G and K dwarf stars of the Pleiades
- Short Name:
- J/ApJS/85/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/432
- Title:
- Fitted UBV magnitude for MS stars
- Short Name:
- J/MNRAS/399/432
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We fit the colour-magnitude diagrams of stars between the zero-age main-sequence and terminal-age main sequence in young clusters and associations. The ages we derive are a factor of 1.5-2 longer than the commonly used ages for these regions, which are derived from the positions of pre-main-sequence stars in colour-magnitude diagrams. From an examination of the uncertainties in the main-sequence and pre-main-sequence models, we conclude that the longer age scale is probably the correct one, which implies that we must revise upwards the commonly used ages for young clusters and associations. Such a revision would explain the discrepancy between the observational lifetimes of protoplanetary discs and theoretical calculations of the time to form planets. It would also explain the absence of clusters with ages between 5 and 30Myr.