We analyze the membership probability of young stars belonging to nearby moving groups with $\textit{Gaia}$ DR2 data. The sample of 1429 stars were identified from 'The Catalog of Suspected Nearby Young Moving Group Stars'. Good-quality parallax and proper motion values were retrieved for 890 stars from $\textit{Gaia}$ DR2 database. The analysis for membership probability is performed in the framework of LACEwING algorithm. From the analysis it is confirmed that 279 stars do not belong to any of the known moving groups. We estimated the $\textit{ U, V, W}$ space velocity values for 250 moving group members, which were found to be more accurate than previous values listed in the literature. The velocity ellipses of all the moving groups are well constrained within the "good box", a widely used criterion to identify moving group members. The age of moving group members are uniformly estimated from the analysis of $\textit{Gaia}$ Color-Magnitude Diagram with MIST isochrones. We found a spread in the age distribution of stars belonging to some moving groups, which needs to be understood from further studies.
Membership of stars in open clusters is one of the most crucial parameters in studies of star clusters. Gaia opened a new window in the estimation of membership because of its unprecedented 6-D data. In the present study, we used published membership data of nine open star clusters as a training set to find new members from Gaia DR2 data using a supervised random forest model with a precision of around 90\%. The number of new members found is often double the published number. Membership probability of a larger sample of stars in clusters is a major benefit in determination of cluster paramete…
The Gaia-ESO Survey (GES) observed many open clusters as part of its programme to spectroscopically characterise the various Milky Way populations. GES spectroscopy and Gaia astrometry from its second data release are used here to assign membership probabilities to targets towards 32 open clusters with ages from 1-3800 Myr, based on maximum likelihood modelling of the 3D kinematics of the cluster and field populations. From a parent catalogue of 14398 individual targets, 5033 stars with uniformly determined 3D velocities, $T_{\rm eff}$, $\log g$ and chemistry are assigned cluster membership wi…
Spectroscopy from the final internal data release of the Gaia-ESO Survey (GES) has been combined with Gaia EDR3 to assign membership probabilities to targets observed towards 63 Galactic open clusters and 7 globular clusters. The membership probabilities are based chiefly on maximum likelihood modelling of the 3D kinematics of the targets, separating them into cluster and field populations. From 43211 observed targets, 13985 are identified as highly probable cluster members ($P>0.9$), with an average membership probability of 0.993. The addition of GES radial velocities successfully drives dow…
In this work, starting from the well-accepted relations in literature, we introduce a new formalism to compute the astrometric membership probabilities for sources in star clusters, and we provide an application to the case of the open cluster M 37. The novelty of our approach is a refined -- and magnitude-dependent -- modelling of the parallax distribution of the field stars. We employ the here-derived list of members to estimate the cluster's mean systemic astrometric parameters, which are based on the most recent Gaia's catalog (EDR3).
We present a study of 7 southern open clusters based on UBVRI CCD photomety (Johnsons-Cousins system) and Gaia DR2 data. Dias 4, Dias 6 and four other clusters had UBVRI photometric observations determined for the first time. From the observational UBVRI data we obtained photometric membership probability estimates and, using the proper motions from the UCAC5 catalog, we also determined the kinematic membership. From Gaia DR2 astrometric data we determine the stellar membership using proper motions and parallaxes, taking into account the full covariance matrix. For both independent sets of dat…
Stars observed in the field of an open cluster are ideal for a controlled test of chemical tagging. Using chemical tagging, one should identify the cluster members, i.e., those stars of similar chemical composition, if their composition is indeed different from that of all the non-member stars of the field. Moreover, the abundance-based membership can be checked against membership based on radial velocities and proper motions. Here, I report preliminary results of such an experiment using data from the Gaia-ESO Survey. Although the three membership criteria usually agree, a few interesting exa…
Gaia EDR3 offers greatly improved kinematics for nearby objects, including members of nearby young stellar moving groups (NYMGs). In this study, we aim to identify low-mass NYMG members (spectral types of M0 to mid-L) in Gaia EDR3. We calculated spatio-kinematic membership probabilities utilising a Bayesian membership probability calculation scheme developed in our previous study. We evaluated stellar youth primarily based on colour-magnitude diagram positions. Combining spatio-kinematic membership assessment and youth evaluation, we identified ~2900 low-mass NYMG candidate members including ~…
Galactic Wolf-Rayet (WR) star membership of star forming regions can be used to constrain the formation environments of massive stars. Here, we utilise $\textit{Gaia}$ DR2 parallaxes and proper motions to reconsider WR star membership of clusters and associations in the Galactic disk, supplemented by recent near-IR studies of young massive clusters. We find that only 18$-$36% of 553 WR stars external to the Galactic Centre region are located in clusters, OB associations or obscured star-forming regions, such that at least 64% of the known disk WR population are isolated, in contrast with only …
Open clusters have long been used to gain insights into the structure, composition, and evolution of the Galaxy. With the large amount of stellar data available for many clusters in the Gaia era, new techniques must be developed for analyzing open clusters, as visual inspection of cluster color-magnitude diagrams is no longer feasible. An automatic tool will be required to analyze large samples of open clusters. We seek to develop an automatic isochrone-fitting procedure to consistently determine cluster membership and the fundamental cluster parameters. Our cluster characterization pipeline f…
We present a study of six open clusters (Berkeley 67, King 2, NGC 2420, NGC 2477, NGC 2682 and NGC 6940) using the Ultra Violet Imaging Telescope (UVIT) aboard \textit{ASTROSAT} and \textit{Gaia} EDR3. We used combinations of astrometric, photometric and systematic parameters to train and supervise a machine learning algorithm along with a Gaussian mixture model for the determination of cluster membership. This technique is robust, reproducible and versatile in various cluster environments. In this study, the \textit{Gaia} EDR3 membership catalogues are provided along with classification of th…
The formation of giant planets is best studied through direct imaging by observing planets both during and after formation. Giant planets are expected to form either by core accretion, which is typically associated with low initial entropy (cold-start models) or by gravitational instability, which corresponds to a high initial entropy of the gas (hot-start models). Thus, constraining the initial entropy provides insight into the planet formation mechanism and determines the resultant brightness evolution. We find that, by observing planets in nearby moving groups of known age both through dire…
Understanding the properties of young open clusters, such as the Initial Mass Function (IMF), star formation history and dynamic evolution, is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process. We want to obtain a list, as complete as possible, of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and, for each method, …
Massive galactic lenses with large Einstein Radii should cause a measurable astrometric microlensing effect, i.e. the light centroid shift due to the motion of the two images. Such a shift in the position of a background star due to microlensing was not included in the $Gaia$ astrometric model, therefore significant deviation should cause $Gaia$'s astrometric parameters to be determined incorrectly. Here we studied one of the photometric microlensing events reported in the $Gaia$ DR3, GaiaDR3-ULENS-001, for which poor goodness of $Gaia$ fit and erroneous parallax could indicate the presence of…
COIN-Gaia 13 is a newly discovered open cluster revealed by Gaia DR2 data. It is a nearby open cluster with a distance of about 513 pc. Combined with the five-dimensional astrometric data of Gaia EDR3 with higher accuracy, we use the membership assignment algorithm (pyUPMASK) to determine the membership of COIN-Gaia 13 in a large extended spatial region. The cluster has found 478 candidate members. After obtaining reliable cluster members, we further study its basic properties and spatial distribution. Our results show that there is an obvious extended structure of the cluster in the X-Y plane…
We examine the capacity to identify binary systems from astrometric deviations alone. We apply our analysis to the Gaia eDR3 and DR2 data, specifically the Gaia Catalogue of Nearby Stars. We show we must renormalize (R)UWE over the local volume to avoid biasing local observations, giving a Local Unit Weight Error (LUWE). We use the simple criterion of LUWE>2, along with a handful of quality cuts to remove likely contaminants, to identify unresolved binary candidates. We identify 22,699 binary candidates within 100 pc of the Sun (just under 10% of sources in this volume). We find an astrometric…
Many open clusters listed in modern catalogues were initially reported by visual astronomers as apparent overdensities of bright stars. As observational techniques and analysis methods continue to improve, some of them have been shown to be chance alignments of stars and not true clusters. Recent publications have provided membership lists for over a thousand clusters, however, many nearby objects listed in the literature have so far evaded detection. We aim to update the Gaia DR2 cluster census by performing membership determinations for known clusters that had been missed by previous studies…
We present mean proper motions and membership probabilities of individual stars for optically visible open clusters, which have been determined using data from the UCAC5 catalog. This follows our previous studies with the UCAC2 and UCAC4 catalogs, but now using improved proper motions in the GAIA reference frame. In the present study results were obtained for a sample of 1108 open clusters. For five clusters, this is the first determination of mean proper motion, and for the whole sample, we present results with a much larger number of identified astrometric member stars than on previous studi…
We investigate the nature of nearby (10-15 kpc) high-speed stars in the Gaia DR2 archive identified on the basis of parallax, proper motion and radial velocity. Together with a consideration of their kinematic, orbital, and photometric properties, we develop a novel strategy for evaluating whether high speed stars are statistical outliers of the bound population or unbound stars capable of escaping the Galaxy. Out of roughly 1.5 million stars with radial velocities, proper motions, and 5-sigma parallaxes, we identify just over 100 high-speed stars. Of these, only two have a nearly 100% chance …
The Gaia-ESO Survey: Calibrating the lithium-age relation with open clusters and associations. II. Expanded cluster sample and final membership selection
We use new data from Gaia DR2 to confirm that the young L1 $γ$ candidate member of the TW Hya association (TWA) is now a bona fide member with a model-dependent mass estimate of ~15 $M_{Jup}$. The ambiguous M9 $γ$ candidate member 2MASS J12474428---3816464 also gets a higher Bayesian membership probability for TWA membership as a result of Gaia DR2 data and a new radial velocity measurement, but it remains unclear whether it is a true member of TWA or if it is an unrelated young interloper, because it is separated by 4.6 km/s from the locus of TWA members in UVW space.
The reality of a field Argus Association has been doubted in some papers in the literature. We apply Gaia DR2 data to stars previously suggested to be Argus members and conclude that a true association exists with age 40-50 Myr and containing many stars within 100 pc of Earth; Beta Leo and 49 Cet are two especially interesting members. Based on youth and proximity to Earth, Argus is one of the better nearby moving groups to target in direct imaging programs for dusty debris disks and young planets.
We used the Tycho-Gaia Astrometric Solution catalogue, part of the Gaia Data Release 1, to search for candidate astrometric microlensing events expected to occur within the remaining lifetime of the Gaia satellite. Our search yielded one promising candidate. We predict that the nearby DQ type white dwarf LAWD 37 (WD 1142-645) will lens a background star and will reach closest approach on November 11th 2019 ($\pm$ 4 days) with impact parameter $380\pm10$ mas. This will produce an apparent maximum deviation of the source position of $2.8\pm0.1$ mas. In the most propitious circumstance, Gaia will…
Blue straggler stars are exotic objects present in all stellar environments whose nature and formation channels are still partially unclear. They seem to be particularly abundant in open clusters (OCs), thus offering a unique chance to tackle these problems statistically.We aim to build up a new and homogeneous catalogue of blue straggler stars (BSS) in Galactic OCs using Gaia to provide a more solid assessment of the membership of these stars. We also aim to explore possible relationships of the straggler abundance with the parent cluster's structural and dynamical parameters. As a by-product…
Aims: Highly resolved maps of the local Galactic dust are an important ingredient for sky emission models. In nearly the whole electromagnetic spectrum one can see imprints of dust, many of which originate from dust clouds within 300pc. Having a detailed 3D reconstruction of these local dust clouds enables detailed studies, helps to quantify the impact on other observables and is a milestone necessary to enable larger reconstructions, as every sightline for more distant objects will pass through the local dust. Methods: To infer the dust density we use parallax and absorption estimates publish…
Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity. We perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open clusters. Based on the par…
The nearest, youngest groups of stars to the Sun provide important samples of age-dated stars for studying circumstellar disk evolution, imaged exoplanets, and brown dwarfs. I briefly comment on the status of the known stellar groups within 100 pc: $β$ Pic, AB Dor, UMa, Car-Near, Tuc-Hor and $β$ Tuc nucleus, Hyades, Col, TW Hya, Car, Coma Ber, 32 Ori, $η$ Cha, and $χ^1$ For. I also discuss some poorly characterized groups and "non-groups." Grades for 2015 of Pass, Satisfactory, or Fail are assigned to the groups for the purposes of age-dating stars and brown dwarfs. I speculate that Tuc-Hor co…
We present a search for stellar members of young associations within 150 pc of the Sun based on Gaia-Tycho and an updated version of the BANYAN $Σ$ software to determine Bayesian membership probabilities that includes Gaia-2MASS color-magnitude diagrams. We identify 32 new F0-M3-type bona fide members of the 10-200 Myr-old Sco-Cen, Carina, Tucana-Horologium, Columba and Octans associations and the AB Doradus, $β$ Pictoris and Carina-Near moving groups. These new bona fide members have measurements of their full kinematics and literature data consistent with a young age. We also confirm the mem…
The Gaia catalogue of nearby stars (GCNS) divided all objects with parallaxes $>$10mas into GCNS-selected and GCNS-rejected 100pc samples. Below the white dwarf (WD) sequence in the complete GCNS color-magnitude diagram (CMD), at $Gabs>14.7+4.7(G-RP)$, there appear 60 GCNS-selected faint blue white dwarfs (FBWDs). However this CMD region is also populated by 411 GCNS-rejected objects, mainly from crowded regions towards the Galactic centre and the Magellanic Clouds. The WD catalog of Gentile Fusillo et al. (2021) lists only 47 GCNS-selected but also 8 GCNS-rejected objects. I confirm 59 of the…
The precise parallax, proper motion, and photometric measurements contained in Gaia Data Release 2 (DR2) offer the opportunity to re-examine the membership and ages of Nearby Young Moving Groups (NYMGs), i.e., loose groups of stars of age $\lesssim100$ Myr in the solar vicinity. Here, we analyze the available DR2 data for members and candidate members of the $ε$ Cha Association ($ε$CA) which, at an estimated age of $\sim$3--5 Myr, has previously been identified as among the youngest NYMGs. The several dozen confirmed members of $ε$CA include MP Mus and T Cha, two of the nearest stars of roughl…
The period versus mass diagrams (i.e., rotational sequences) of open clusters provide crucial constraints for angular momentum evolution studies. However, their memberships are often heavily contaminated by field stars, which could potentially bias the interpretations. In this paper, we use data from Gaia DR2 to re-assess the memberships of seven open clusters with ground- and space-based rotational data, and present an updated view of stellar rotation as a function of mass and age. We use the Gaia astrometry to identify the cluster members in phase-space, and the photometry to derive revised …
Only four star clusters are known within ~100 pc of Earth. Of these, the Chi1 For cluster has barely been studied. We use the Gaia DR2 catalog and other published data to establish the cluster membership, structure, and age. The age of and distance to the cluster are ~40 Myr and 104 pc, respectively. A remarkable, unprecedented, aspect of the cluster is the large percentage of M-type stars with warm excess infrared emission due to orbiting dust grains -- these stars lie in an annulus that straddles the tidal radius of the cluster. The Chi1 For cluster appears to be closely related to two exten…
There are 88 stars which lack colours, but have measured parallaxes in \textit{Gaia} EDR3 that place them within 20\,pc from the sun. Among them we found two new common parallax and proper motion (CPPM) companions separated from their primaries by about 3\,arcsec. The CPPM companion of a nearby ($d=14.98$\,pc) F1 star, \object{HD 105452 B}, was already imaged with the \textit{Hubble Space Telescope} and is now confirmed with \textit{Gaia} data and photometrically classified by us as M4 dwarf. The other CPPM companion, \object{SCR J1214-2345 B} orbiting an M4.5 dwarf at $d=10.77$\,pc, represent…
The public, all-sky surveys Gaia and TESS provide the ability to identify new young associations and determine their ages. These associations enable study of planetary evolution by providing new opportunities to discover young exoplanets. A young association was recently identified by Tang et al. and F{ü}rnkranz et al. using astrometry from Gaia (called "Group-X" by the former). In this work, we investigate the age and membership of this association; and we validate the exoplanet TOI 2048 b, which was identified to transit a young, late G dwarf in Group-X using photometry from TESS. We first i…
Binary systems can evolve into immensely different exotic systems such as blue straggle stars (BSSs), yellow straggler stars, cataclysmic variables, type Ia supernovae depending on their initial mass, the orbital parameters and evolution. The aim of this thesis is to understand the demographics of post-mass-transfer systems (BSSs, white dwarfs and blue lurkers) present in the open clusters and how they are formed. First, we identified the cluster members using Gaia EDR3 data in six open clusters. Two of the clusters, M67 and King2, were studied in detail using UVIT, Gaia, GALEX, 2MASS and othe…
The membership determination for open clusters in noisy environments of the Milky Way is still an open problem. In this paper, our main aim is provide the membership probability of stars using proper motions and parallax values of stars using Gaia EDR3 astrometry. Apart from the Gaia astrometry, we have also used other photometric data sets like UKIDSS, WISE, APASS and Pan-STARRS1 in order to understand cluster properties from optical to mid-infrared regions. We selected 438 likely members with membership probability higher than $50\%$ and G$\le$20 mag. We obtained the mean value of proper mot…
The high-precision astrometry from the second data release of the Gaia mission has made it possible to greatly improve the census of members of nearby clusters and associations. I have applied the Gaia data to the Taurus star-forming region, refining the sample of known members and identifying candidates for undiscovered members. The resulting samples of members and candidates provide the best constraints to date on the distribution of ages and the initial mass function (IMF) in Taurus. Several studies over the last 30 years have proposed the existence of a population of older stars (>=10 Myr)…
The Galex Nearby Young Star Survey (GALNYSS) has yielded a sample of $\sim$2000 UV-selected objects that are candidate nearby ($D \stackrel{<}{\sim}$150 pc), young (age $\sim$10--100 Myr), late-type stars. Here, we evaluate the distances and ages of the subsample of (19) GALNYSS stars with Gaia Data Release 1 (DR1) parallax distances $D \le 120$ pc. The overall youth of these 19 mid-K to early-M stars is readily apparent from their positions relative to the loci of main sequence stars and giants in Gaia-based color-magnitude and color-color diagrams constructed for all Galex- and WISE-detected…
Young nearby runaway stars are suitable to search for their place of origin and possibly associated objects, for example neutron stars. Tetzlaff, Neuhäuser & Hohle (2011) selected young ($\le 50$ Myr) runaway star candidates from Hipparcos, for which they had estimated the ages from the location in the Hertzsprung-Russell diagram and evolutionary models. Here, we redetermine or constrain their young ages more precisely not only by using the new Gaia DR2 data, but also by measuring lithium, which is a youth indicator. For 308 stars, we took spectra to search for the strong resonance doublet of …
The Star Formation in Nearby Clouds (SFiNCs) project is aimed at providing detailed study of the young stellar populations and star cluster formation in nearby 22 star forming regions (SFRs) for comparison with our earlier MYStIX survey of richer, more distant clusters. As a foundation for the SFiNCs science studies, here, homogeneous data analyses of the Chandra X-ray and Spitzer mid-infrared archival SFiNCs data are described, and the resulting catalogs of over 15300 X-ray and over 1630000 mid-infrared point sources are presented. On the basis of their X-ray/infrared properties and spatial d…
Reliable fundamental parameters of open clusters such as distance, age and extinction are key to our understanding of Galactic structure and stellar evolution. In this work we use {\it Gaia} DR2 to investigate 45 open clusters listed in the \emph{New catalogue of optically visible open clusters and candidates} (DAML) but with no previous astrometric membership estimation based on {\it Gaia} DR2. In the process of selecting targets for this study we found that some clusters reported as new discoveries in recent papers based on {\it Gaia} DR2 were already known clusters listed in DAML. Cluster m…
Lee & Song (2018, Paper 1) developed a tool for calculating Bayesian membership probability for nearby young stellar moving groups (BAMG: Bayesian Analysis of Moving Groups). The study presented the importance of careful construction of models in moving group membership assessment, using $β$ Pictoris moving group as a test case. In this study, we build models for all major nearby young stellar moving groups (NYMGs hereafter) through 4 stages. A set of prototype models is created using members listed in the discovery paper of each group. For each group, suggested members after the discovery of …
We analysed the open clusters Czernik 2 and NGC 7654 using CCD UBV photometric and Gaia Early Data Release 3 (EDR3) photometric and astrometric data. Structural parameters of the two clusters were derived, including the physical sizes of Czernik 2 being r=5 and NGC 7654 as 8 min. We calculated membership probabilities of stars based on their proper motion components as released in the Gaia EDR3. To identify member stars of the clusters, we used these membership probabilities taking into account location and the impact of binarity on main-sequence stars. We used membership probabilities higher …
Fundamental parameters and physical processes leading to the formation of white dwarfs (WDs) may be constrained and refined by discovering WDs in open clusters (OCs). Cluster membership can be utilized to establish the precise distances, luminosities, ages, and progenitor masses of such WDs. We compile a list of probable WDs that are OC members in order to facilitate WD studies that are impractical or difficult to conduct for Galactic field WDs. We use recent catalogs of WDs and OCs that are based on the second data release of the \textit{Gaia} satellite mission (GDR2) to identify WDs that are…
This white paper proposes leveraging high-quality Gaia data available to the worldwide scientific community and complement it with support from Canadian-related facilities to place Canada as a leader in the fields of stellar associations and exoplanet science, and to train Canadian highly qualified personnel through graduate and post-graduate research grants. Gaia has sparked a new era in the study of stellar kinematics by measuring precise distances and proper motions for 1.3 billion stars. These data have already generated more than 1700 scientific papers and are guaranteed to remain the sou…
In this research note we identify 130 new M-type candidate members of young associations with the BANYAN $Σ$ tool and recently published trigonometric distances from RECONS and URAT-South. We identify a white dwarf candidate in the AB Doradus moving group, but determine that its cooling age is too large and reject it as a member. Three stars (G 13-39, LHS 2935 and G 152-1) now have complete kinematics and are strong candidate members in the AB Doradus and Carina-Near moving groups, but still lack a confirmation of their young age independent of their kinematics.
We derive relative proper motions of stars in the fields of the globular clusters M12, NGC 6362, M4, M55, M22, NGC 6752, NGC 3201, M30, M10, NGC 362, M5, and 47 Tucanae based on data collected between 1997 and 2015 with the 1-m Swope telescope of Las Campanas Observatory. We determine membership class and membership probability for over 446 000 objects, and show that these are efficient methods for separating field stars from members of the cluster. In particular, membership probabilities of variable stars and blue/yellow/red stragglers are determined. Finally, we find absolute proper motions …
