- ID:
- ivo://CDS.VizieR/J/A+A/644/A49
- Title:
- Gaia18aen light and velocity curves
- Short Name:
- J/A+A/644/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Besides the astrometric mission of the Gaia satellite, its repeated and high-precision measurements also serve as an all-sky photometric transient survey. The sudden brightenings of the sources are published as Gaia Photometric Science Alerts and are made publicly available, allowing the community to photometrically and spectroscopically follow up on the object. The goal of this paper is to analyze the nature and derive the basic parameters of Gaia18aen, a transient detected at the beginning of 2018. This object coincides with the position of the emission-line star WRAY 15-136. The brightening was classified as a "nova?" on the basis of a subsequent spectroscopic observation. We analyzed two spectra of Gaia18aen and collected the available photometry of the object covering the brightenings in 2018 and also the preceding and following periods of quiescence. Based on this observational data, we derived the parameters of Gaia18aen and discussed the nature of the object. Gaia18aen is the first symbiotic star discovered by Gaia satellite. The system is an S-type symbiotic star and consists of an M giant of a slightly super-solar metallicity, where Teff~3500K, a radius of ~230R_{sun}_, and a high luminosity L~7400L_{sun}_. The hot component is a hot white dwarf. We tentatively determined the orbital period of the system 487d. The main outburst of Gaia18aen in 2018 was accompanied by a decrease in the temperature of the hot component. The first phase of the outburst was characterized by the high luminosity L~27000L_{sun}_, which remained constant for about three weeks after the optical maximum, later followed by the gradual decline of luminosity and increase of temperature. Several re-brightenings have been detected on the timescales of hundreds of days.
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Search Results
- 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/AJ/161/87
- Title:
- Gaia data for members of {epsilon}Cha
- Short Name:
- J/AJ/161/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The precise parallax, proper motion, and photometric measurements contained in Gaia Data Release 2 (DR2) offer the opportunity to reexamine the membership and ages of nearby young moving groups (NYMGs), i.e., loose groups of stars of age <~100Myr in the solar vicinity. Here, we analyze the available DR2 data for members and candidate members of the {epsilon}Cha Association ({epsilon}CA) which, at an estimated age of ~3-5Myr, has previously been identified as among the youngest NYMGs. The several dozen confirmed members of {epsilon}CA include MPMus and TCha, two of the nearest stars of roughly solar mass that are known to host primordial protoplanetary disks, and the Herbig Ae/Be star HD104237A. We have used Gaia DR2 data to ascertain the Galactic positions and kinematics and color-magnitude diagram positions of {epsilon}CA members and candidates so as to reassess their membership status and thereby refine estimates of the distance, age, multiplicity, and disk fraction of the group. Our analysis yields 36 bona fide {epsilon}CA members, as well as 20 provisional members, including 3 new members identified here as comoving companions to previously known {epsilon}CA stars. We determine a mean distance to {epsilon}CA of 101.0{+/-}4.6pc and confirm that, at an age of 5_-2_^+3^Myr, {epsilon}CA represents the youngest stellar group within ~100pc of Earth. We identify several new photometric binary candidates, bringing the overall multiplicity fraction (MF) of {epsilon}CA to 40%, intermediate between the MFs of young T associations and the field.
445. Gaia DR2
- ID:
- ivo://CDS.VizieR/I/345
- Title:
- Gaia DR2
- Short Name:
- I/345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gaia Data Release 2. Summary of the contents and survey properties: We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on as- trophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the G_BP_ (330-680nm) and G_RP_ (630-1050nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy. The catalogue of radial velocity standard stars (Soubiran et al., 2018A&A...616A...7S) The Radial Velocity Spectrometer (RVS) on board of Gaia having no calibration device, the zero point of radial velocities needs to be calibrated with stars proved to be stable at the level of 300m/s during the Gaia observations. A dataset of about 71000 ground-based radial velocity measurements from five high resolution spectrographs has been compiled. A catalogue of 4813 stars was built by combining these individual measurements. The zero point has been established using asteroids. The resulting catalogue has 7 observations per star on average on a typical time baseline of 6 years, with a median standard deviation of 15m/s. A subset of the most stable stars fulfilling the RVS requirements has been used to establish the zero point of the radial velocities provided in Gaia DR2. The stars not used for calibration are used for the RVS data validation.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A48
- Title:
- Gaia-DR2 extended kinematical maps. I.
- Short Name:
- J/A+A/621/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Gaia Collaboration has used Gaia-DR2 sources with six-dimensional (6D) phase space information to derive kinematical maps within 5kpc of the Sun, which is a reachable range for stars with relative error in distance lower than 20%. Here we aim to extend the range of distances by a factor of two to three, thus adding the range of Galactocentric distances between 13kpc and 20kpc to the previous maps, with their corresponding error and root mean square values. We make use of the whole sample of stars of Gaia-DR2 including radial velocity measurements, which consists in more than seven million sources, and we apply a statistical deconvolution of the parallax errors based on the Lucy's inversion method of the Fredholm integral equations of the first kind, without assuming any prior. The new extended maps provide lots of new and corroborated information about the disk kinematics: significant departures of circularity in the mean orbits with radial Galactocentric velocities between -20 and +20km/s and vertical velocities between -10 and +10km/s; variations of the azimuthal velocity with position; asymmetries between the northern and the southern Galactic hemispheres, especially towards the anticenter that includes a larger azimuthal velocity in the south; and others. These extended kinematical maps can be used to investigate the different dynamical models of our Galaxy, and we will present our own analyses in the forthcoming second part of this paper. At present, it is evident that the Milky Way is far from a simple stationary configuration in rotational equilibrium, but is characterized by streaming motions in all velocity components with conspicuous velocity gradients.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A7
- Title:
- Gaia DR2 radial velocity standard stars catalog
- Short Name:
- J/A+A/616/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Radial Velocity Spectrometer (RVS) on board the ESA satellite mission Gaia has no calibration device. Therefore, the radial velocity zero point needs to be calibrated with stars that are proved to be stable at a level of 300m/s during the Gaia observations. We compiled a dataset of ~71000 radial velocity measurements from five high-resolution spectrographs. A catalogue of 4813 stars was built by combining these individual measurements. The zero point was established using asteroids. The resulting catalogue has seven observations per star on average on a typical time baseline of 6yr, with a median standard deviation of 15m/s. A subset of the most stable stars fulfilling the RVS requirements was used to establish the radial velocity zero point provided in Gaia Data Release 2. The stars that were not used for calibration are used to validate the RVS data.
- 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}.
450. Gaia EDR3
- ID:
- ivo://CDS.VizieR/I/350
- Title:
- Gaia EDR3
- Short Name:
- I/350
- Date:
- 18 Jan 2022 09:31:17
- Publisher:
- CDS
- Description:
- Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase. Survey completeness: The Gaia EDR3 catalogue is essentially complete between G=12 and G=17. The source list for the release is incomplete at the bright end and has an ill-defined faint magnitude limit, which depends on celestial position. The combination of the Gaia scan law coverage and the filtering on data quality which will be done prior to the publication of Gaia EDR3, does lead to some regions of the sky displaying source density fluctuations that reflect the scan law pattern. In addition, small gaps exist in the source distribution, for instance close to bright stars. Astrometry: The parallax improvement is typically 20% with respect to Gaia DR2. The proper motions are typically a factor two better than in Gaia DR2. An overall reduction of systematics has been achieved. E.g., the parallax zero point deduced from the extragalactic sources is about -20{mu}as. A tentative correction formula for the parallax zero point will be provided. Closer to the release date of Gaia Early Data Release 3, an update will be given on the astrometry. Photometry: The G-band photometric uncertainties are ~0.25mmag for G<13, 1mmag at G=17, and 5mmag at G=20mag. The GBP-band photometric uncertainties are ~1mmag for G<13, 10mmag at G=17, and 100mmag at G=20mag. The GRP-band photometric uncertainties are ~1mmag for G<13, 5mmag at G=17, and 50mmag at G=20mag. Closer to the release date of Gaia Early Data Release 3, an update will be given on the photometry. Gaia EDR3 does not contain new radial velocities. The radial velocities of Gaia Data Release 2 have been added to Gaia EDR3 in order to ease the combination of spectrosopic and astrometric data. Radial velocities: Gaia EDR3 hence contains Gaia DR2 median radial velocities for about 7.21 million stars with a mean G magnitude between ~4 and ~13 and an effective temperature (Teff) in the range ~3550 to 6900K. The overall precision of the radial velocities at the bright end is of the order of ~200-300m/s while at the faint end, the overall precision is ~1.2km/s for a Teff of 4750K and ~3.5km/s for a Teff of 6500K. Before publication in Gaia EDR3, an additional filtering has been performed onto the Gaia DR2 radial velocities to remove some 4000 sources that had wrong radial velocities. Please be aware that the Gaia DR2 values are assigned to the Gaia EDR3 sources through an internal cross-match operation. In total, ~10000 Gaia DR2 radial velocities could not be associated to a Gaia EDR3 source. Astrophysical parameters: Gaia EDR3 does not contain new astrophysical parameters. Astrophysical parameters have been published in Gaia DR2 and a new set is expected to be released with the full Gaia DR3 release. Variable stars: Gaia EDR3 does not contain newly classified variable stars. For the overview of the currently available variable stars from Gaia DR2, have a look here. Classifications for a larger set of variable stars are expected with the full Gaia DR3 release. Solar system objects: A large set of solar system objects with orbits will become available with the full Gaia DR3 release. Information on the currently available asteroids in Gaia DR2 can be found here. Documentation: Data release documentation is provided along with each data release in the form of a downloadable PDF and a webpage. The various chapters of the documentation have been indexed at ADS allowing them to be cited. Please visit the Gaia Archive (https://gea.esac.esa.int/archive) to access this documentation, and make sure to check out all relevant information given through the documentation overview page (https://www.cosmos.esa.int/web/gaia-users/archive).
