We investigate the frequency of occurrence of Galactic carbon stars as a function of progenitor mass using Gaia data. Small number statistics limit fidelity, but C star frequency agrees with that observed in the Magellanic Clouds (MCs) down to $m \approx1.67$ M$_\odot$. At $m \approx 1.38$ M$_\odot$, the frequency rises by a factor of three even though the frequency appears to drop to zero for the MCs. In fact this is due to a lack of clusters at the key age range in the MCs. At $m \approx 1.24$ M$_\odot$ and below, no C stars are observed, corresponding to ages older than 4 Gyr. Within uncertainties, C~star frequency in M 31 is consistent with that of the Galaxy and the MCs. We find an ambiguous C-star candidate at $\sim$7 M$_\odot$.
Membership of stars in open clusters is one of the most crucial parameters in studies of star clusters. Gaia opened a new window in the estimation of membership because of its unprecedented 6-D data. In the present study, we used published membership data of nine open star clusters as a training set to find new members from Gaia DR2 data using a supervised random forest model with a precision of around 90\%. The number of new members found is often double the published number. Membership probability of a larger sample of stars in clusters is a major benefit in determination of cluster paramete…
COIN-Gaia 13 is a newly discovered open cluster revealed by Gaia DR2 data. It is a nearby open cluster with a distance of about 513 pc. Combined with the five-dimensional astrometric data of Gaia EDR3 with higher accuracy, we use the membership assignment algorithm (pyUPMASK) to determine the membership of COIN-Gaia 13 in a large extended spatial region. The cluster has found 478 candidate members. After obtaining reliable cluster members, we further study its basic properties and spatial distribution. Our results show that there is an obvious extended structure of the cluster in the X-Y plane…
Spectroscopy from the final internal data release of the Gaia-ESO Survey (GES) has been combined with Gaia EDR3 to assign membership probabilities to targets observed towards 63 Galactic open clusters and 7 globular clusters. The membership probabilities are based chiefly on maximum likelihood modelling of the 3D kinematics of the targets, separating them into cluster and field populations. From 43211 observed targets, 13985 are identified as highly probable cluster members ($P>0.9$), with an average membership probability of 0.993. The addition of GES radial velocities successfully drives dow…
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…
Context. Selecting a cluster in proper motion space is an established method for identifying members of a star forming region. The first data release from Gaia (DR1) provides an extremely large and precise stellar catalogue, which when combined with the Tycho-2 catalogue gives the 2.5 million parallaxes and proper motions contained within the Tycho-Gaia Astrometric Solution (TGAS). Aims. We aim to identify new member candidates of the nearby Upper Scorpius subgroup of the Scorpius-Centaurus Complex within the TGAS catalogue. In doing so, we also aim to validate the use of the DBSCAN clustering…
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…
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…
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 ~…
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…
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 …
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 pilot study of Galactic globular cluster (GC) proper motion (PM) determinations using Gaia data. We search for GC stars in the Tycho-Gaia Astrometric Solution (TGAS) catalogue from Gaia Data Release 1 (DR1), and identify five members of NGC104 (47 Tucanae), one member of NGC5272 (M3), five members of NGC6121 (M4), seven members of NGC6397, and two members of NGC6656 (M22). By taking a weighted average of member stars, fully accounting for the correlations between parameters, we estimate the parallax (and, hence, distance) and PM of the GCs. This provides a homogeneous PM study of …
Identifying the young optically visible population in a star-forming region is essential for fully understanding the star formation event. In this paper, We identify 211 candidate members of the Perseus molecular cloud based on Gaia astronomy. We use LAMOST spectra to confirm that 51 of these candidates are new members, bringing the total census of known members to 856. The newly confirmed members are less extincted than previously known members. Two new stellar aggregates are identified in our updated census. With the updated member list, we obtain a statistically significant distance gradien…
(abridged) NGC6530 is a young cluster with a complex morphology and star-formation history. We present a statistical study of its global properties using a new large list of candidate members down to masses of 0.2-0.4 Msun and Gaia DR2 astrometry. We consider a wider sky region compared to previous studies, to investigate the whole cluster and its neighborhood. We study the distribution of extinction and age across the different regions, and obtain constraints on the star-formation history. Cluster membership is determined on the basis of X-ray data, H-alpha emission, near-IR and UV excesses f…
In this work we present a method to identify possible members of globular clusters using data from Gaia DR2. The method consists of two stages: the first one based on a clustering algorithm, and the second one based on the analysis of the projected spatial distribution of stars with different proper motions. In order to confirm that the clusters members extracted by the method correspond to actual globular clusters, the spatial distribution, the vector point diagram of the proper motions and the colour-magnitude diagrams are analysed. We apply the developed method to eight clusters: NGC 1261, …
We have refined the census of stars and brown dwarfs in the Upper Sco association (~10 Myr, ~145 pc) by 1) updating the selection of candidate members from our previous survey to include the high-precision astrometry from the second data release of Gaia, 2) obtaining spectra of a few hundred candidate members to measure their spectral types and verify their youth, and 3) assessing the membership (largely with Gaia astrometry) of 2020 stars toward Upper Sco that show evidence of youth in this work and previous studies. We arrive at a catalog of 1761 objects that are adopted as members of Upper …
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…
Sco OB2 is the nearest OB association, extending over approximately 2000 sq.deg. on the sky. Only its brightest members are already known (from Hipparcos) across its entire size, while studies of its lower-mass population refer only to small portions of its extent. In this work we exploit the capabilities of Gaia DR2 measurements to search for Sco OB2 members across its entire size and down to the lowest stellar masses. We use both Gaia astrometric and photometric data to select association members, using minimal assumptions derived mostly from the Hipparcos studies. Gaia resolves small detail…
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…
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 …
In this study we follow up our recent paper (Monteiro et al. 2020) and present a homogeneous sample of fundamental parameters of open clusters in our Galaxy, entirely based on Gaia DR2 data. We used published membership probability of the stars derived from Gaia DR2 data and applied our isochrone fitting code, updated as in Monteiro et al. (2020), to GB and GR Gaia DR2 data for member stars. In doing this we take into account the nominal errors in the data and derive distance, age, and extinction of each cluster. This work therefore provides parameters for 1743 open clusters and, as a byproduc…
We present a detailed photometric and kinematical analysis of poorly studied open cluster IC 1434 using CCD VRI, APASS, and Gaia DR2 database for the first time. BY determining the membership probability of stars, we identified the 238 most probable members with a probability higher than 60% by using proper motion and parallax data as taken from the Gaia DR2 catalog. The mean proper motion of the cluster is obtained as emu_x= - 3.89 +/- 0.19 and emu_y= - 3.34 +/- 0.19 mas/yr in both the directions of right ascension and declination. The radial distribution of member stars provides cluster exte…
The Ophiuchus cloud complex is one of the best laboratories to study the earlier stages of the stellar and protoplanetary disc evolution. The wealth of accurate astrometric measurements contained in the Gaia Data Release 2 can be used to update the census of Ophiuchus member candidates. We seek to find potential new members of Ophiuchus and identify those surrounded by a circumstellar disc. We constructed a control sample composed of 188 bona fide Ophiuchus members. Using this sample as a reference we applied three different density-based machine learning clustering algorithms (DBSCAN, OPTICS,…
We characterize twelve young stellar objects (YSOs) located in the Lupus I region, spatially overlapping with the Upper Centaurus Lupus (UCL) sub-stellar association. The aim of this study is to understand whether the Lupus I cloud has more members than what has been claimed so far in the literature and gain a deeper insight into the global properties of the region. We selected our targets using Gaia DR2 catalog, based on their consistent kinematic properties with the Lupus I bona fide members. In our sample of twelve YSOs observed by X-Shooter, we identified ten Lupus I members. We could not …
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, …
The solar neighborhood contains disc stars that have recently crossed spiral arms in the Galaxy. We propose that boundaries in local velocity distributions separate stars that have recently crossed or been perturbed by a particular arm from those that haven't. Ridges in the stellar velocity distributions constructed from the second Gaia data release trace orbits that could have touched nearby spiral arms at apocentre or pericentre. The multiple ridges and arcs seen in local velocity distributions are consistent with the presence of multiple spiral features and different pattern speeds and impl…
Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about 7 kpc. Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey. New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster. Gaia-ESO Survey data for 142 potential members, lying on the upper MS and on the red clump, yielded radial velocity measurements, which, together with prope…
We investigate the star formation history of the IC1396 region by studying its kinematics and completing the population census. We use multiwavelength data, combining optical spectroscopy (to identify and classify new members), near-infrared photometry (to trace shocks, jets, and outflows and the interactions between the cluster members and the cloud), along with Gaia EDR3 to identify new potential members in the multidimensional proper motion/parallax space. The revised Gaia EDR3 distance is 925$\pm$73 pc, slightly closer than previously obtained with DR2. The Gaia data reveal four distinct s…
In very young clusters, stellar age distribution is the empirical proof of the duration of star formation (SF) and of the physical mechanisms involved in the process. We derived accurate stellar ages for the cluster NGC6530, associated with the Lagoon Nebula to infer its SF history. We use the Gaia-ESO survey observations and Gaia DR2 data, to derive cluster membership and fundamental stellar parameters. We identified 652 confirmed and 9 probable members. The reddening inferred for members and non-members allows us to distinguish MS stars and giants, in agreement with the distances inferred fr…
Context: The $χ^{1}$ Fornacis cluster (Alessi 13) is one of a few open clusters of its age and distance in the Solar neighbourhood that ought to benefit from more attention as it can serve as a cornerstone for numerous future studies related to star and planet formation. Aims: We take advantage of the early installment of the third data release of the Gaia space mission in combination with archival data and our own observations, to expand the census of cluster members and revisit some properties of the cluster. Methods: We applied a probabilistic method to infer membership probabilities over a…
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…
We search through an eight-million cubic-parsec volume surrounding the Pleiades star cluster and the Sun to identify both the current and past members of the Pleiades cluster within the Gaia EDR3 dataset. We find nearly 1,300 current cluster members and 289 former cluster candidates. Many of these candidates lie well in front or behind the cluster from our point of view, so formerly they were considered cluster members, but their parallaxes put them more than 10 pc from the centre of the cluster today. Over the past 100 Myr we estimate that the cluster has lost twenty percent of its mass inclu…
Open clusters are groups of stars that form at the same time, making them an ideal laboratory to test theories of star formation, stellar evolution, and dynamics in the Milky Way disk. However, the utility of an open cluster can be limited by the accuracy and completeness of its known members. Here, we employ a "top-down" technique, {\it extreme deconvolution gaussian mixture models} (XDGMM), to extract and evaluate known open clusters from Gaia DR2 by fitting the distribution of stellar parallax and proper motion along a line-of-sight. Extreme deconvolution techniques can recover the intrinsi…
With the photometric data from the SDSS survey, the spectroscopic data from the SDSS/SEGUE and the LAMOST surveys, and the astrometric data from the Gaia DR2, we have identified 71 highly-probable member stars of the GD-1 cold stellar stream spread along almost its entire length (i.e. from 126 to 203 degree in Right Ascension). With the accurate spectroscopic (i.e. metallicity and line-of-sight velocity) and astrometric (i.e. proper motions) information, the position-velocity diagrams, i.e. $ϕ_{1}$-$μ_α$, $ϕ_{1}$-$μ_δ$ and $ϕ_{1}$-${v_{\rm gsr}}$, of the GD-1 stream are well mapped. The stream…
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…
Re-visiting the Canis Major star-forming region with Gaia data release 3 data
Universidade Cidade de São Paulo（圣保罗城市大学）；Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo（圣保罗大学天文、地球物理与大气科学研究所）；Universidad Nacional de Educación a Distancia (UNED)（西班牙国立远程教育大学）；Université de Bordeaux（波尔多大学）；Institut universitaire de France (IUF)（法国高等教育研究院）
$Context$. Gaia Second Data Release provides precise astrometry and photometry for more than 1.3 billion sources. This catalog opens a new era concerning the characterization of open clusters and test stellar models, paving the way for a better understanding of the disc properties. $Aims$. The aim of the paper is to improve the knowledge of cluster parameters, using only the unprecedented quality of the Gaia photometry and astrometry. $Methods$. We make use of the membership determination based on the precise Gaia astrometry and photometry. We apply anautomated Bayesian tool, BASE-9, to fit st…
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 …
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 phenomenon of interaction between planetary nebulae (PNe) and the interstellar medium (ISM) is one of the significant issues in the field of astrophysics. The main objective of this paper is to verify the interaction process for objects that have been known as interacting PNe (IPNe) in the literature. This study is based on parallax and proper motion observations facilitated recently by the early third data release of the Gaia space mission. Based on the proper nebular central star (CS) motion towards the region of interaction between the PN and ISM, we were able to verify the interaction …
Context: Trumpler 23 is a moderately populated, intermediate-age open cluster within the solar circle at a Rgc ~6 kpc. It is in a crowded field very close to the Galactic plane and the color-magnitude diagram shows significant field contamination and possible differential reddening; it is a relatively understudied cluster for these reasons, but its location makes it a key object for determining Galactic abundance distributions. Aims: New data from the Gaia-ESO Survey enable the first ever radial velocity and spectroscopic metallicity measurements for this cluster. We aim to use velocities to i…
We report 1,656 new star clusters found in the Galactic disk (|b|<20 degrees) beyond 1.2 kpc, using Gaia EDR3 data. Based on an unsupervised machine learning algorithm, DBSCAN, and followed our previous studies, we utilized a unique method to do the data preparation and obtained the clustering coefficients, which proved to be an effective way to search blindly for star clusters. We tabulated the physical parameters and member stars of the new clusters, and presented some interesting examples, including a globular cluster candidate. The cluster parameters and member stars are available at CDS v…
We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of open clusters as age calibrators. We perform a homogeneous analysis of eight open clusters using the Gaia-DR1 TGAS catalogue for bright members, and information from the Gaia-ESO Survey for fainter stars. Cluster membership probabilities for the Gaia-ESO Survey targets are derived based on several spectroscopic tracers. The Gaia-ESO Survey also provides the …
The global survey of star clusters in the Milky Way (MWSC) is a comprehensive list of 3061 objects that provides, among other parameters, distances to clusters based on isochrone fitting. The Tycho-Gaia Astrometric Solution (TGAS) catalogue, which is a part of Gaia data release 1 (Gaia DR1), delivers accurate trigonometric parallax measurements for more than 2 million stars, including those in star clusters. We compare the open cluster photometric distance scale with the measurements given by the trigonometric parallaxes from TGAS to evaluate the consistency between these values. The average p…
We show how astrometric and spectroscopic errors introduced by an unresolved binary system can be combined to give estimates of the binary period and mass ratio. This can be performed analytically if we assume we see one or more full orbits over our observational baseline, or numerically for all other cases. We apply this method to Gaia DR3 data, combining the most recent astrometric and spectroscopic data. We compare inferred periods and mass ratios calculated using our method with orbital parameters measured for non-single stars in Gaia DR3 and find good agreement. Finally, we use this metho…
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…
