TY - JOUR A1 - Anders, Friedrich A1 - Khalatyan, Arman A1 - Queiroz, Anna B. A. A1 - Chiappini, Cristina A1 - Ardèvol, Judith A1 - Casamiquela, Laia A1 - Figueras, Francesca A1 - Jiménez-Arranz, Óscar A1 - Jordi, Carme A1 - Monguio, Maria A1 - Romero-Gómez, Merce A1 - Altamirano, Diego A1 - Antoja, Teresa A1 - Assaad, R. A1 - Cantat-Gaudin, Tristan A1 - Castro-Ginard, Alfred A1 - Enke, Harry A1 - Girardi, Léo A1 - Guiglion, Guillaume A1 - Khan, Saniya A1 - Luri, Xavier A1 - Miglio, Andrea A1 - Minchev, Ivan A1 - Ramos, Pau A1 - Santiago, Basillio Xavier A1 - Steinmetz, Matthias T1 - Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G=18.5 JF - Astronomy and astrophysics N2 - We present a catalogue of 362 million stellar parameters, distances, and extinctions derived from Gaia's Early Data Release (EDR3) cross-matched with the photometric catalogues of Pan-STARRS1, SkyMapper, 2MASS, and All WISE. The higher precision of the Gaia EDR3 data, combined with the broad wavelength coverage of the additional photometric surveys and the new stellar-density priors of the StarHorse code, allows us to substantially improve the accuracy and precision over previous photo-astrometric stellar-parameter estimates. At magnitude G = 14 (17), our typical precisions amount to 3% (15%) in distance, 0.13 mag (0.15 mag) in V-band extinction, and 140 K (180 K) in effective temperature. Our results are validated by comparisons with open clusters, as well as with asteroseismic and spectroscopic measurements, indicating systematic errors smaller than the nominal uncertainties for the vast majority of objects. We also provide distance- and extinction-corrected colour-magnitude diagrams, extinction maps, and extensive stellar density maps that reveal detailed substructures in the Milky Way and beyond. The new density maps now probe a much greater volume, extending to regions beyond the Galactic bar and to Local Group galaxies, with a larger total number density. We publish our results through an ADQL query interface (gaia . aip . de) as well as via tables containing approximations of the full posterior distributions. Our multi-wavelength approach and the deep magnitude limit render our results useful also beyond the next Gaia release, DR3. KW - stars: distances KW - stars: fundamental parameters KW - Galaxy: general KW - Galaxy: stellar content KW - Galaxy: structure Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202142369 SN - 0004-6361 SN - 1432-0746 VL - 658 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Culpan, Rick A1 - Pelisoli, Ingrid A1 - Geier, Stephan T1 - Clean catalogues of blue horizontal-branch stars using Gaia EDR3 JF - Astronomy and astrophysics : an international weekly journal / European Southern Observatory (ESO) N2 - Context. Blue horizontal-branch stars evolve from low-mass stars that have completed their main-sequence lifetimes and undergone a helium flash at the end of their red-giant phase. As such, blue horizontal-branch stars are very old objects that can be used as markers in studies of the Galactic structure and formation history. To create a clean sky catalogue of blue horizontal-branch stars, we cross-matched the Gaia data release 2 (DR2) dataset with existing reference catalogues to define selection criteria based on Gaia DR2 parameters. Following the publication of Gaia early data release 3 (EDR3), these methods were verified and subsequently applied to this latest release. Aims. Previous catalogues of blue horizontal-branch stars were developed using spectral analyses or were restricted to individual globular clusters. The purpose of this catalogue is to identify a set of blue horizontal-branch star candidates that have been selected using photometric and astrometric observations and exhibits a low contamination rate. This has been deemed important as the success of the Gaia mission has changed the way that targets are selected for large-scale spectroscopic surveys, meaning that far fewer spectra will be acquired for blue horizontal-branch stars in the future unless they are specifically targeted.
Methods. We cross-matched reference blue horizontal-branch datasets with the Gaia DR2 database and defined two sets of selection criteria. Firstly, in Gaia DR2 - colour and absolute G magnitude space, and secondly, in Gaia DR2 - colour and reduced proper motion space. The main-sequence contamination in both subsets of the catalogue was reduced, at the expense of completeness, by concentrating on the Milky Way's Galactic halo, where relatively young main-sequence stars were not expected. The entire catalogue is limited to those stars with no apparent neighbours within 5 arcsec. These methods were verified and subsequently applied to the Gaia EDR3. Results. We present a catalogue, based on Gaia EDR3, of 57 377 blue horizontal-branch stars. The Gaia EDR3 parallax was used in selecting 16 794 candidates and the proper motions were used to identify a further 40 583 candidates. KW - Hertzsprung-Russell and C-M diagrams KW - stars: horizontal-branch KW - catalogs KW - Galaxy: stellar content Y1 - 2021 U6 - https://doi.org/10.1051/0004-6361/202040074 SN - 1432-0746 VL - 654 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Sander, Andreas Alexander Christoph A1 - Hamann, Wolf-Rainer A1 - Todt, Helge Tobias A1 - Hainich, Rainer A1 - Shenar, Tomer A1 - Ramachandran, Varsha A1 - Oskinova, Lidia M. T1 - The Galactic WC and WO stars BT - The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors JF - Astronomy and astrophysics : an international weekly journal N2 - Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star parameters is of major importance for several astrophysical fields. With Gaia DR2, for the first time parallaxes for a large sample of Galactic WC stars are available, removing major uncertainties inherent to earlier studies. In this work, we re-examine a previously studied sample of WC stars to derive key properties of the Galactic WC population. All quantities depending on the distance are updated, while the underlying spectral analyzes remain untouched. Contrasting earlier assumptions, our study yields that WC stars of the same subtype can significantly vary in absolute magnitude. With Gaia DR2, the picture of the Galactic WC population becomes more complex: We obtain luminosities ranging from log L/L-circle dot = 4.9-6.0 with one outlier (WR 119) having log L/L-circle dot = 4.7. This indicates that the WC stars are likely formed from a broader initial mass range than previously assumed. We obtain mass-loss rates ranging between log(M) over dot = -5.1 and -4.1, with (M) over dot proportional to L-0.68 and a linear scaling of the modified wind momentum with luminosity. We discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the WR radius problem, and the open questions in regard to the connection of WR stars with Gamma-ray bursts. WC and WO stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a WO stage. KW - stars: evolution KW - stars: mass-loss KW - stars: Wolf-Rayet KW - stars: massive KW - stars: distances KW - Galaxy: stellar content Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201833712 SN - 1432-0746 VL - 621 PB - EDP Sciences CY - Les Ulis ER -