- ID:
- ivo://CDS.VizieR/J/ApJ/889/99
- Title:
- Gaia DR2 Blanco 1 member candidates
- Short Name:
- J/ApJ/889/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar population, using Gaia DR2 parallax, kinematics, and photometry, of the young (~100Myr), nearby (~230pc) open cluster, Blanco 1. A total of 644 member candidates are identified via the unsupervised machine learning method StarGO to find the clustering in the 5-dimensional position and proper motion parameter (X, Y, Z, {mu}{alpha}*cos{delta}, {mu}{delta}) space. Within the tidal radius of 10.0+/-0.3pc, there are 488 member candidates, 3 times more than those outside. A leading tail and a trailing tail, each of 50-60pc in the Galactic plane, are found for the first time for this cluster, with stars further from the cluster center streaming away faster, manifest stellar stripping. Blanco 1 has a total detected mass of 285+/-32M_{sun}_ with a mass function consistent with a slope of alpha=1.35+/-0.2 in the sense of dN/dm{prop.to}m^-alpha^, in the mass range of 0.25-2.51M_{sun}_, where N is the number of members and $m$ is stellar mass. A Minimum Spanning Tree ({LAMBDA}_MSR_) analysis shows the cluster to be moderately mass segregated among the most massive members (>~1.4M_{sun}_), suggesting an early stage of dynamical disintegration.
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- ID:
- ivo://CDS.VizieR/J/A+A/630/A119
- Title:
- Gaia DR2 distances to two clusters
- Short Name:
- J/A+A/630/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the one hand, the second data release of the Gaia mission (GaiaDR2, Cat. I/345) has opened a trove of astrometric and photometric data for Galactic clusters within a few kpc of the Sun. On the other hand, lucky imaging has been an operational technique to measure the relative positions of visual binary systems for a decade and a half, a time sufficient to apply its results to the calculation of orbits of some massive multiple systems within ~1kpc of the Sun. As part of an ambitious research program to measure distances to Galactic stellar groups (including clusters) containing O stars,I start with two of the nearest examples: Collinder 419 in Cygnus and NGC 2264 in Monoceros. The main ionizing source for both clusters is a multiple system with an O-type primary: HD 193322 and 15 Mon, respectively. For each of those two multiple systemsI aim to derive new astrometric orbits for the Aa,Ab components. First, I present a method that usesGaiaDR2 G+G_BP_+G_RP_ photometry, positions, proper motions, and parallaxes to obtain the membership and distance of a stellar group and apply it to Collinder 419 and NGC 2264. Second, I present a new code that calculates astrometric orbits by searching the whole seven-parameter orbit space and apply it to HD 193 322 Aa,Ab and 15 Mon Aa,Abusing as input literature data from the Washington Double Star Catalog (WDS) and the AstraLux measurements recently presented by Maiz Apellaniz et al. (2019, Cat. J/A+A/626/A20) I obtain GaiaDR2 distances of 1006^+37^_-34_pc for Collinder 419 and 719+/-16pc for NGC 2264, with the main contribution to the uncertainties coming from the spatial covariance of the parallaxes. The two NGC 2264 subclusters are at the same distance (within the uncertainties) and they show a significant relative proper motion. The distances are shown to be robust. HD 193322 Aa,Ab follows an eccentric (e=0.58^+0.03^_-0.04_) orbit with a period of 44+/-1 a and the three stars it contains have a total mass of 76.1^+9.9^_-7.4_M_{sun}_. The orbit of 15 Mon Aa,Ab is even more eccentric (e=0.770^+0.023^_-0.030_), with a period of 108+/-12 a and a total mass of 45.1^+3.6^_-3.3_M_{sun}_ for its two stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/502/L90
- Title:
- Gaia DR2 Galactic bulge new star clusters
- Short Name:
- J/MNRAS/502/L90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 34 new open clusters and candidates as a result of a systematic search carried out in 200 adjacent fields of 1x1 square degrees area projected towards the Galactic bulge, using Gaia DR2 data. The objects were identified and characterized by a joint analysis of their photometric, kinematic and spatial distribution, which has been consistently used and proved to be effective in our previous works. The discoveries were validated by cross-referencing the objects position and astrometric parameters with the available literature. Besides their coordinates and astrometric parameters, we also provide sizes, ages, distances and reddening for the discovered objects. In particular, 32 clusters are closer than 2kpc from the Sun, which represents an increment of nearly 39% of objects with astrophysical parameters determined in the nearby inner disk. Although these objects fill an important gap in the open clusters distribution along the Sagittarius arm, this arm, traced by known clusters, appears to be interrupted, which may be an artifact due to the incompleteness of the cluster census.
- 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/MNRAS/489/3093
- Title:
- Gaia DR2 parallax of globular clusters
- Short Name:
- J/MNRAS/489/3093
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have established a mixture model approach to derive the parallax of the MilkyWay globular clusters. It avoids the problem of cluster membership determination and provides a completely independent astrometrical solution by purely using the parallax data. This method is validated with simulated clusters of Pancino et al.. We have resolved 120 real globular clusters by the mixture model using parallaxes of the second data release of Gaia. They construct the largest direct parallax sample up to now. In comparison with other direct parallax results based on cluster members, including 75 clusters of Gaia Collaboration, our method presents its accuracy, especially for some particular clusters. A systematic offset of -27.6+/-1.7 uas, together with a scatter of 22.8+/-1.3 uas is found in comparison with other indirect parallax measurements. They are consistent with the global value and the variation of the zero-point of current Gaia parallaxes. Distances of several specific nearby globular clusters are discussed while the closest ones can reach high precisions, even taking the systematic error into account.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/89
- Title:
- Gaia DR2 PMs of stars in ultra-faint MW satellites
- Short Name:
- J/ApJ/863/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second data release from the Gaia mission (DR2) provides a comprehensive and unprecedented picture of the motions of astronomical sources in the plane of the sky, extending from the solar neighborhood to the outer reaches of the Milky Way. I present proper-motion measurements based on Gaia DR2 for 17 ultra-faint dwarf galaxies within 100kpc of the Milky Way. I compile the spectroscopically confirmed member stars in each dwarf bright enough for Gaia astrometry from the literature, producing member samples ranging from two stars in Triangulum II to 68 stars in Bootes I. From the spectroscopic member catalogs, I estimate the proper motion of each system. I find good agreement with the proper motions derived by the Gaia collaboration for Bootes I and Leo I. The tangential velocities for 14 of the 17 dwarfs are determined to better than 50km/s, more than doubling the sample of such measurements for Milky Way satellite galaxies. The orbital pericenters are well constrained, with a mean value of 38kpc. Only one satellite, Tucana III, is on an orbit passing within 15kpc of the Galactic center, suggesting that the remaining ultra-faint dwarfs are unlikely to have experienced severe tidal stripping. As a group, the ultra-faint dwarfs are on high-velocity, eccentric, retrograde trajectories, with nearly all of them having space motions exceeding 370km/s. A large majority of the objects are currently close to the pericenters of their orbits. In a low-mass (M_vir_=0.9x10^12^M_{sun}_) Milky Way potential, eight out of the 17 galaxies lack well-defined apocenters and appear likely to be on their first infall, indicating that the Milky Way mass may be larger than previously estimated or that many of the ultra-faint dwarfs are associated with the Magellanic Clouds. The median eccentricity of the ultra-faint dwarf orbits is 0.79, similar to the values seen in numerical simulations but distinct from the rounder orbits of the more luminous dwarf spheroidals.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A52
- Title:
- Gaia DR1 QSO magnitude
- Short Name:
- J/A+A/611/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first release of the Gaia catalog is available since 14 September 2016. It is a first step in the realization of the future Gaia reference frame. This reference frame will be materialized by the optical positions of the sources and will be compared with and linked to the International Celestial Reference Frame, materialized by the radio position of extragalactic sources. As in the radio domain, it can be reasonably postulated that quasar optical flux variations can alert us to potential changes in the source structure. These changes could have important implications for the position of the target photocenters (together with the evolution in time of these centers) and in parallel have consequences for the link of the reference systems. A set of nine optical telescopes was used to monitor the magnitude variations, often at the same time as Gaia, thanks to the Gaia Observation Forecast Tool. The Allan variances, which are statistical tools widely used in the atomic time and frequency community, are introduced.
- ID:
- ivo://CDS.VizieR/J/AJ/160/138
- Title:
- 68 Gaia DR2 ultra-short-period planet host stars
- Short Name:
- J/AJ/160/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has been unambiguously shown both in individual systems and at the population level that hot Jupiters experience tidal inspiral before the end of their host stars main-sequence lifetimes. Ultra-short-period (USP) planets have orbital periods P<1 day, rocky compositions, and are expected to experience tidal decay on similar timescales to hot Jupiters if the efficiency of tidal dissipation inside their host stars parameterized as Q_*_' is independent of P and/or secondary mass M_p_. Any difference between the two classes of systems would reveal that a model with constant Q_*_' is insufficient. If USP planets experience tidal inspiral, then USP planet systems will be relatively young compared to similar stars without USP planets. Because it is a proxy for relative age, we calculate the Galactic velocity dispersions of USP planet candidate host and non-host stars using data from Gaia Data Release 2 supplemented with ground-based radial velocities. We find that main-sequence USP planet candidate host stars have kinematics consistent with similar stars in the Kepler field without observed USP planets. This indicates that USP planet hosts have similar ages to field stars and that USP planets do not experience tidal inspiral during the main-sequence lifetimes of their host stars. The survival of USP planets requires that Q_*_'>~10^7^ at P~0.7day and M_p_~2.6M{Earth}. This result demands that Q_*_' depend on the orbital period and/or mass of the secondary in the range 0.5day<~P<~5days and 1M{Earth}<~M_p_<~1000M{sun}.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/4570
- Title:
- Gaia DR2 white dwarf candidates
- Short Name:
- J/MNRAS/482/4570
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of white dwarf candidates selected from the second data release of Gaia (DR2). We used a sample of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey (SDSS) to map the entire space spanned by these objects in the Gaia Hertzsprung-Russell diagram. We then defined a set of cuts in absolute magnitude, colour, and a number of Gaia quality flags to remove the majority of contaminating objects. Finally, we adopt a method analogous to the one presented in our earlier SDSS photometric catalogues to calculate a probability of being a white dwarf (PWD) for all Gaia sources which passed the initial selection. The final catalogue is composed of 486641 stars with calculated PWD from which it is possible to select a sample of~260000 high-confidence white dwarf candidates in the magnitude range 8<G<21. By comparing this catalogue with a sample of SDSS white dwarf candidates we estimate an upper limit in completeness of 85 per cent for white dwarfs with G<=20mag and Teff>7000K, at high Galactic latitudes (|b|>20deg). However, the completeness drops at low Galactic latitudes, and the magnitude limit of the catalogue varies significantly across the sky as a function of Gaia's scanning law. We also provide the list of objects within our sample with available SDSS spectroscopy.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/83
- Title:
- 723 Gaia DR2 White dwarfs cand. in Local Galactic Halo
- Short Name:
- J/ApJ/899/83
- Date:
- 14 Mar 2022 08:58:44
- Publisher:
- CDS
- Description:
- We present a catalog of 531 white dwarf candidates that have large apparent transverse motions relative to the Sun (v_T_>200km/s), thus making them likely members of the local Galactic halo population. The candidates were selected from the Gaia Data Release 2 and are located in a great circle with 20{deg} width running across both Galactic poles and the Galactic center and anticenter, a zone that spans 17.3% of the sky. The selection used a combination of kinematic and photometric properties, derived primarily from Gaia proper motions, G magnitudes, and G_BP_-G_RP_ color, and including parallax whenever available. Additional validation of the white dwarf candidates is made using PanSTARRS photometric (gri) data. Our final catalog includes not only stars having full kinematic and luminosity estimates from reliable Gaia parallax, but also stars with presently unreliable or no available Gaia parallax measurements. We argue that our method of selecting local halo objects with and without reliable parallax data leads us to round up all possible halo white dwarfs in the Gaia catalog (in that particular section of the sky) with recorded proper motions >40mas/yr and that pass our v_T_>200km/s threshold requirement. We expect this catalog will be useful for the study of the white dwarf population of the local Galactic halo.
