Open Clusters Research Articles

Making hot Jupiters in stellar clusters – II. Efficient formation in binary systems

ABSTRACT Observations suggested that the occurrence rate of hot Jupiters (HJs) in open clusters is largely consistent with the field ($\sim 1{{\ \rm per\ cent}}$) but in the binary-rich cluster M67, the rate is $\sim 5{{\ \rm per\ cent}}$. How does the cluster environment boost HJ formation via the high-eccentricity tidal migration initiated by the extreme-amplitude von Zeipel–Lidov–Kozai (XZKL) mechanism forced by a companion star? Our analytical treatment shows that the cluster’s collective gravitational potential alters the companion’s orbit slowly, which may render the star–planet–companion configuration XZKL-favourable. We have also performed direct Gyr N-body simulations of the star cluster evolution and XZKL of planets’ orbit around member stars. We find that an initially single star may acquire a companion star via stellar scattering and the companion may enable XZKL in the planets’ orbit. Planets around an initially binary star may also be XZKL-activated by the companion. In both scenarios, the companion’s orbit has likely been significantly changed by stellar scattering and the cluster potential before XZKL occurs. Across different cluster models, 0.8–3 per cent of the planets orbiting initially single stars have experienced XZKL while the fraction is 2–26 per cent for initially binary stars. Around a star that is binary at 1 Gyr, 13–32 per cent of its planets have undergone XZKL, and combined with single stars, the overall XZKL fraction is 3–21 per cent, most affected by the cluster binarity. If 10 per cent of the stars in M67 host a giant planet, our model predicts an HJ occurrence rate of $\sim 1{{\ \rm per\ cent}}$. We suggest that HJ surveys target old, high-binarity, not-too-dense open clusters and prioritize wide binaries to maximize HJ yield.

Spectral study of the planetary nebula NGC 2452

We provide a detailed study for the Galactic planetary nebula (PN) NGC 2452, which has long been suspected to be a member of the Galactic cluster NGC2453. The present study uses integral field unit (IFU) spectroscopic observations of the PN to explore its physical conditions, chemical abundances, kinematical characteristics, and morphological features. The strength of the singly ionized helium (HeII λ4686) line reveals that the PN is of high excitation class. The presence of the neutral lines of [OI] and [NI] a long with the value of the flux ratio F([Nii]λ6583)/F(Hα) indicates that the object is slightly optically thick. We compute the nebular density and temperature from a large number of diagnostic line ratios. The ionic and total abundances of helium (He) and carbon (C) are derived from their optical recombination lines (ORLs), while the abundances of nitrogen (N), oxygen (O), neon (Ne), argon (Ar), sulphur (S), and chlorine (Cl) are derived from their collisionlly-excitation lines (CELs). Faint lines like Krypton (Kr), Manganese (Mn), and Chromium (Cr), which are known to be products of the slow-process (s-process), are also seen in the PN spectrum. To illustrate the morphology and excitation structures of the PN, we generate a gallery of emission-line maps using the nebular data cubes. We find that the PN has an overall elliptical shape with a few interior clumps. In terms of physical and chemical properties, we find no significant differences between the entire PN and its accompanying clumps, considering the uncertainties associated with these parameters. Both the astronomical data from Gaia and the inferred radial velocity suggest that the PN belongs to the Galactic thin-disk.

Conformal covariance of connection probabilities and fields in 2D critical percolation

AbstractFitting percolation into the conformal field theory framework requires showing that connection probabilities have a conformally invariant scaling limit. For critical site percolation on the triangular lattice, we prove that the probability that n vertices belong to the same open cluster has a well‐defined scaling limit for every . Moreover, the limiting functions transform covariantly under Möbius transformations of the plane as well as under local conformal maps, that is, they behave like correlation functions of primary operators in conformal field theory. In particular, they are invariant under translations, rotations and inversions, and for any . This implies that and , for some constants C2 and C3.We also define a site‐diluted spin model whose n‐point correlation functions Cn can be expressed in terms of percolation connection probabilities and, as a consequence, have a well‐defined scaling limit with the same properties as the functions . In particular, . We prove that the magnetization field associated with this spin model has a well‐defined scaling limit in an appropriate space of distributions. The limiting field transforms covariantly under Möbius transformations with exponent (scaling dimension) 5/48. A heuristic analysis of the four‐point function of the magnetization field suggests the presence of an additional conformal field of scaling dimension 5/4, which counts the number of percolation four‐arm events and can be identified with the so‐called “four‐leg operator” of conformal field theory.

Finding the dispersing siblings of young open clusters. Dynamical traceback simulations using Gaia DR3

Finding the dispersing siblings of young open clusters. Dynamical traceback simulations using Gaia DR3

The unusual planetary nebula nucleus in the Galactic open cluster M37 and six further hot white dwarf candidates

Planetary nebulae in Galactic open star clusters are rare objects; only three are known to date. They are of particular interest because their distance can be determined with high accuracy, allowing one to characterize the physical properties of the planetary nebula and its ionizing central star with high confidence. Here we present the first quantitative spectroscopic analysis of a central star in an open cluster, namely the faint nucleus of IPHASX J055226.2+323724 in M37. This cluster contains 14 confirmed white dwarf members, which were previously used to study the initial-to-final-mass relation of white dwarfs, and six additional white dwarf candidates. We performed an atmosphere modeling of spectra taken with the 10m Gran Telescopio Canarias. The central star is a hot hydrogen-deficient white dwarf with an effective temperature of 90 000 K and spectral type PG1159 (helium- and carbon-rich). We know it is about to transform into a helium-rich DO white dwarf because the relatively low atmospheric carbon abundance indicates ongoing gravitational settling of heavy elements. The star belongs to a group of hot white dwarfs that exhibit ultrahigh-excitation spectral lines possibly emerging from shock-heated material in a magnetosphere. We find a relatively high stellar mass of M = 0.85−0.14+0.13 M⊙. This young white dwarf is important for the semi-empirical initial-final mass relation because any uncertainty related to white-dwarf cooling theory is insignificant with respect to the pre-white-dwarf timescale. Its post-asymptotic-giant-branch age of 170 000–480 000 yr suggests that the extended planetary nebula is extraordinarily old. We also performed a spectroscopic analysis of the six other white dwarf candidates of M37, confirming one as a cluster member.

Young nearby open clusters and their luminosity functions

Context. Open clusters are groups of coeval stars sharing properties such as distance and metallicity, and they are key to understanding stellar evolution. Aims. Our main goal is to study the evolution of open clusters with a special focus on the universality of the luminosity function. Methods. We applied an upgraded version of the convergent point technique on about 50 open clusters. The selection of cluster members was based purely on the exquisite astrometry of the Gaia DR3 and HIPPARCOS catalogues in the five-dimensional or full six-dimensional space. Results. We present updated lists of bona fide members of ∼50 open clusters within 500 pc and younger than 1 Gyr, exploiting the full depth of the third Gaia data release complemented by HIPPARCOS at the bright end, excluding regions in the Galactic plane. Our catalogues also are complemented by optical and infrared photometry from the major large-scale public surveys. All the data will be made available on a dedicated webpage with interactive plots and a direct link to Aladin and Vizier hosted at the Centre de Données de Strasbourg. We derived luminosity functions for all bound clusters and compared them in three age groups of ∼50 Myr, ∼150 Myr, and ∼600 Myr, discussing similarities and differences to constrain their dynamical evolution. Conclusions. Luminosity functions of clusters at 50 Myr are more likely similar to each other and show a greater degree of similarity than older clusters. We explain this observation with the universal luminosity function within the volume of our sample (500 pc). Luminosity functions of clusters with ages similar to the Pleiades or Hyades are more diverse, perhaps due to internal dynamical evolution, but more work is needed to provide additional evidence.

Impact of the Galactic bar on tidal streams within the Galactic disc

Tidal streams of disrupted clusters are powerful probes of the gravitational potential of the Galaxy and they are routinely detected in the stellar halo of the Milky Way. It was recently shown that tidal streams of open clusters can now also be detected within the Milky Way disc. In this work, we highlight the fact that disc tidal streams also provide a powerful new diagnostic of the non-axisymmetric disc potential and may, in principle, provide a new constraint on the pattern speed of the Galactic bar. In particular, we show how the stream-orbit misalignment for an open cluster on a quasi-circular disk orbit in the solar vicinity varies as a function of the position with respect to the bar resonances. The angular shift rises beyond corotation, reaching values as high as 30° close to the outer Lindblad resonance (OLR), then dropping again and reversing its sign beyond the OLR. We applied this mechanism to the recently detected tidal stream of the Hyades open cluster and we note that the detected stream stars would be very similar when taking a potential a priori with no bar or with a fast pattern speed of 55 km s−1 kpc−1 (or lower than 30 km s−1 kpc−1). However, we find that candidate stream stars are different than previously detected ones when adopting a potential with a bar pattern speed of 39 km s−1 kpc−1, which is consistent with the most recent determinations of the actual Galactic bar pattern speed. Previously detected Hyades candidate members would, on the other hand, favour a barless galaxy or a fast bar of pattern speed 55 km s−1 kpc−1. Interestingly, the previously reported asymmetry in star counts within the leading and trailing tails of the Hyades tidal stream persists in all cases. Our study conclusively demonstrates that the effect of disc non-axisymmetries cannot be neglected when searching for tidal streams of open clusters and that current candidate members of the Hyades stream should not be trusted beyond a distance of 200 pc from the cluster. Moreover, our study allows for ideal targets to be provided for high-resolution spectroscopy follow-ups, which will enable conclusive identifications of the Hyades stream track and provide novel independent constraints on the bar pattern speed in the Milky Way.

An Extremely Massive White Dwarf Escaped from the Hyades Star Cluster

We searched the Gaia DR3 database for ultramassive white dwarfs with kinematics consistent with having escaped the nearby Hyades open cluster, identifying three such candidates. Two of these candidates have masses estimated from Gaia photometry of approximately 1.1 solar masses; their status as products of single-stellar evolution that have escaped the cluster was deemed too questionable for immediate follow-up analysis. The remaining candidate has an expected mass >1.3 solar masses, significantly reducing the probability of it being an interloper. Analysis of follow-up Gemini GMOS spectroscopy for this source reveals a nonmagnetized hydrogen atmosphere white dwarf with a mass and age consistent with having formed from a single star. Assuming a single-stellar-evolution formation channel, we estimate a 97.8% chance that the candidate is a true escapee from the Hyades. With a determined mass of 1.317 solar masses, this is potentially the most massive known single-evolution white dwarf and is by far the most massive with a strong association with an open cluster.

ASTROPHYSICAL STUDIES OF 9 UNSTUDIED OPEN STAR CLUSTERS USING GAIA DR3

Using the Gaia DR3 data sets, this work gives an analysis of nine open clusters: Dolidze 25, Kronberger 13, Kronberger 18, Majaess 99, NGC 7795, Ruprecht 139, Teutsch 55, S1, and FSR 0596, which are close to the Galactic plane of the Milky Way. The number of probable cluster members is found to be 81, 77, 120, 155, 108, 110, 160, and 116 respectively. Radii are determined as 5.40, 5.25, 4.80, 4.20, 4.28, 3.70, 4.30, 4.30, and 3.53 arcmin, respectively. With solar metallicity isochrones log ages of 7.70, 9.00, 8.35, 7.50, 9.00, 8.00, 7.50, 8.50, and 9.5 yr are determined for these clusters. The best fitting of the isochrone produced distances of 2.6, 1.27, 1.16, 1.16, 3.10, 1.64, 2.50, 2.44, and 0.98 kpc that are similar to the distances calculated from inverting median parallaxes. The mass function slopes are in agreement with the Salpeter value. The results of the total masses are found to be 116.07, 79.33, 141.24, 147.34, 145.76, 491.01, 155, 212.46, and 82.79 M☉.

Outskirts of Abell 1795: Probing gas clumping in the intracluster medium

Contact. The outskirts of galaxy clusters host complex interactions between the intracluster and circumcluster media. During the evolution of clusters, ram-pressure stripped gas clumps from infalling substructures break the uniformity of the gas distribution, potentially leading to observational biases at large radii. However, assessing the contribution of gas clumping poses observational challenges and requires robust X-ray measurements in the background-dominated regime of the cluster outskirts. Aims. The main objectives of this study are to isolate faint gas clumps from field sources and from the diffuse emission in the Abell 1795 galaxy cluster, then to probe their impact on the observed surface brightness and thermodynamic profiles. Methods. We performed an imaging analysis on deep Chandra ACIS-I observations of the Abell 1795 cluster outskirts, extending out to ∼1.5r200 with full azimuthal coverage. We built the 0.7 − 2.0 keV surface brightness distribution from the adaptively binned image of the diffuse emission and looked for clumps in the form of > + 2σ surface brightness outliers. Our classification of the clump candidates was based primarily on Chandra and SDSS data. Benefiting from the point source list resolved by Chandra, we extracted the thermodynamic profiles of the intracluster medium from the associated Suzaku XIS data out to r200 using multiple point source and clump candidate removal approaches. Results. We identified 24 clump candidates in the Abell 1795 field, most of which are likely to be associated with background objects, including active galactic nuclei, galaxies, and clusters or groups of galaxies, as opposed to intrinsic gas clumps. These sources had minimal impact on the surface brightness and thermodynamic profiles of the cluster emission. After correcting for clump candidates, the measured entropy profile still deviates from a pure gravitational collapse, suggesting complex physics at play in the outskirts, which may include potential electron–ion non-equilibrium and non-thermal pressure support.

A DEEP STUDY OF THE OPEN CLUSTER NGC 5288 USING PHOTOMETRIC AND ASTROMETRIC DATA FROM GAIA DR3 AND 2MASS

This paper investigates a poorly studied open cluster, NGC 5288, using 2MASS JHKS and the recently released Gaia DR3 astrometric and photometric data. The mean proper motions in right ascension and declination are estimated as (-3.840 ± 0.230) and (-1.934 ± 0.162) mas yr-1 respectively. We also derive the age and distance of the cluster as 510 ± 190 Myr and 2.64 ± 0.11 kpc, using color-magnitude diagrams (CMDs). We also obtain the distance as 2.77 ± 0.42 kpc using the parallax method. Interstellar reddening E(B ‒ V) in the direction of the cluster is determined as 0.45 mag using the ((J ‒ H), (J ‒ K)) color-color diagram. We find the mass function slope for main-sequence stars as 1.39 ± 0.29 within the mass range 1.0-2.7 M☉, which agrees with Salpeter's value within the uncertainty. Galactic orbits are derived using the Galactic potential model, indicating that NGC 5288 follows a circular path around the Galactic center.

Uncovering new white dwarf–open cluster associations using Gaia DR3

Context. Open clusters (OCs) provide homogeneous samples of white dwarfs (WDs) with known distances, extinctions, and total ages. The unprecedented astrometric precision of Gaia allows us to identify many novel OC–WD pairs. Studying WDs in the context of their parent OCs makes it possible to determine the properties of WD progenitors and study the initial–final mass relation (IFMR). Aims. We seek to find potential new WD members of OCs in the solar vicinity. The analysis of OC members’ parallaxes allows us to determine the OC distances to a high precision, which in turn enables us to calculate WD masses and cooling ages and to constrain the IFMR. Methods. We searched for new potential WD members of nearby OCs using the density-based machine learning clustering algorithm HDBSCAN. The clustering analysis was applied in five astrometric dimensions – positions in the sky, proper motions and parallaxes, and in three dimensions where the positional information was not considered in the clustering analysis. The identified candidate OC WDs were further filtered using the photometric criteria and properties of their putative host OCs. The masses and cooling ages of the WDs were calculated via a photometric method using all available Gaia, Pan-STARRS, SDSS, and GALEX photometry. The WD progenitor masses were determined using the ages and metallicities of their host OCs. Results. Altogether, 63 OC WD candidates were recovered, 27 of which are already known in the literature. We provide characterization for 36 novel WDs that have significant OC membership probabilities. Six of them fall into relatively unconstrained sections of the IFMR where the relation seems to exhibit nonlinear behavior. We were not able to identify any WDs originating from massive progenitors that would even remotely approach the widely adopted WD progenitor mass limit of 8 M⊙; this confirms the paucity of such objects residing in OCs and hints at a presence of velocity kicks for nascent WDs.

C3PO: towards a complete census of co-moving pairs of stars – I. High precision stellar parameters for 250 stars

ABSTRACT We conduct a line-by-line differential analysis of a sample of 125 co-moving pairs of stars (dwarfs and subgiants near solar metallicity). We obtain high-precision stellar parameters with average uncertainties in effective temperature, surface gravity, and metallicity of 16.5 K, 0.033 and 0.014 dex, respectively. We classify the co-moving pairs of stars into two groups, chemically homogeneous (conatal; |Δ[Fe/H]| ≤ 0.04 dex) and inhomogeneous (non-conatal), and examine the fraction of chemically homogeneous pairs as a function of separation and effective temperature. The four main conclusions from this study are (1) A spatial separation of Δs = 106 au is an approximate boundary between homogeneous and inhomogeneous pairs of stars, and we restrict our conclusions to only consider the 91 pairs with Δs ≤ 106 au; (2) There is no trend between velocity separation and the fraction of chemically homogeneous pairs in the range Δv ≤ 4 km s−1; (3) We confirm that the fraction of chemically inhomogeneous pairs increases with increasing Teff and the trend matches a toy model of that expected from planet ingestion; (4) Atomic diffusion is not the main cause of the chemical inhomogeneity. A major outcome from this study is a sample of 56 bright co-moving pairs of stars with chemical abundance differences ≤ 0.02 dex (5 per cent) which is a level of chemical homogeneity comparable to that of the Hyades open cluster. These important objects can be used, in conjunction with star clusters and the Gaia ‘benchmark’ stars, to calibrate stellar abundances from large-scale spectroscopic surveys.

Extragalactic electromagnetic cascades and cascade gamma-ray emission in magnetic fields of various strength

We discuss the magnetic field influence on diffuse gamma-ray emission from extragalactic electromagnetic cascades initiated by ultra-high energy cosmic rays. Regions in space vary considerably in field strength: it is possibly of 10−12 G and lower in voids, of ∼10−6 G inside galaxies, galactic clusters and groups, of ∼10−7 G around them, and of ∼10−8–10−9 G in filaments. Structures having fields higher than in voids occupy comparatively small fraction of the Universe, so they affect weakly on cascade emission. Still knowledge of this influence may be relevant studying large-scale component of the extragalactic magnetic field and to the search for exotic particles, as in the latter case contribution of all components to extragalactic gamma-ray background should be known, one of which is cascade emission. To study magnetic field effect we simulate particle propagation in homogeneous magnetic field of ∼10−6, 10−9, and 10−12 G and lower. It is found that in fields of ∼10−9 G and lower the spectra of diffuse cascade gamma-rays at energies E ≤ 1017 eV coincide. Thus no specific models of EGMF are required to study contribution of cascade emission in the extragalactic gamma-ray background at E ≤ 1017 eV. In the case of uniform field of 10−6 G (which seems to be unrealistic), this inference is valid in the energy range of ∼107109 eV. Results obtained can be also used studying large-scale component of the extragalactic magnetic field.

Revisiting Galactic Disk and Spiral Arms Using Open Clusters

We use the largest catalog of open clusters in the post-Gaia era to provide an observational view of the Galactic disk. By compiling physical parameters such as age, distance, and kinematic information, we investigate the spatial distribution of open clusters and revisit the spiral arms and other asymmetries in the Galactic disk. Using young open clusters as a tracer of spiral arms, we map the spiral structure of the Galaxy and find that most of the clusters start migrating away from the spiral arms in about 10–20 Myr and fill the interarm regions as they age. Using the 3D kinematic information on 371 open star clusters, we derive different individual pattern speeds for spiral arms that closely follow the rotation curve of the Milky Way, hence favoring the transient nature of spiral arms in the Milky Way. The pattern rotation speeds of each spiral arm suggest that the spiral arms have not accelerated in the last 80 Myr. Based on the distribution of open clusters younger than 700 Myr above or below the Galactic plane, we found a solar offset of z ⊙ = 17.0 ± 0.9 pc north of the Galactic plane and estimated the scale height z h = 91.7 ± 1.9 pc from the Galactic plane.

Chemical abundances of the young inner-disc open cluster NGC 6705 observed by APOGEE: sodium-rich and not α-enhanced

ABSTRACT Previous results in the literature have found the young inner-disc open cluster NGC 6705 to be mildly α-enhanced. We examined this possibility via an independent chemical abundance analysis for 11 red-giant members of NGC 6705. The analysis is based on near-infrared APOGEE spectra and relies on LTE calculations using spherical model atmospheres and radiative transfer. We find a mean cluster metallicity of $\rm [Fe/H] = +0.13 \pm 0.04$, indicating that NGC 6705 is metal-rich, as may be expected for a young inner-disc cluster. The mean α-element abundance relative to iron is $\rm \langle [\alpha /Fe]\rangle =-0.03 \pm 0.05$, which is not at odds with expectations from general Galactic abundance trends. NGC 6705 also provides important probes for studying stellar mixing, given its turn-off mass of M ∼ 3.3 M⊙. Its red giants have low 12C abundances ([12C/Fe] = −0.16) and enhanced 14N abundances ([14N/Fe] = +0.51), which are key signatures of the first dredge-up on the red giant branch. An additional signature of dredge-up was found in the Na abundances, which are enhanced by [Na/Fe] = +0.29, with a very small non-LTE correction. The 16O and Al abundances are found to be near-solar. All of the derived mixing-sensitive abundances are in agreement with stellar models of approximately 3.3 M⊙ evolving along the red giant branch and onto the red clump. As found in young open clusters with similar metallicities, NGC 6705 exhibits a mild excess in the s-process element cerium with $\rm [Ce/Fe] = +0.13\pm 0.07$.

Directional Shunting of Photogenerated Carriers in POM@MOF for Promoting Nitrogen Adsorption and Oxidation.

The efficient catalysis of nitrogen (N2 ) into high-value N-containing products plays a crucial role in the N economic cycle. However, weak N2 adsorption and invalid N2 activation remain two major bottlenecks in rate-determining steps, leading to low N2 fixation performance. Herein, an effective dual active sites photocatalyst of polyoxometalates (POMs)-based metal-organic frameworks (MOFs) is highlighted via altering coordination microenvironment and inducing directional shunting of photogenerated carriers to facilitate N2 /catalyst interaction and enhance oxidation performance. MOFs create more open unsaturated metal cluster sites with unoccupied d orbital possessing Lewis acidity to accept electrons from the 3σg bonding orbital of N2 for storage by combining with POMs to replace bidentate linkers. POMs act as electron sponges donating electrons to MOFs, while the holes directional flow to POMs. The hole-rich POMs with strong oxidation capacity are easily involved in oxidizing adsorbed N2 . Taking UiO-66 (C48 H28 O32 Zr6 ) and Mo72 Fe30 ([Mo72 Fe30 O252 (CH3 COO)12 {Mo2 O7 (H2 O)}2 {H2 Mo2 O8 (H2 O)}(H2 O)91 ]·150H2 O) as an example, Mo72 Fe30 @UiO-66 shows twofold enhanced adsorption of N2 (250.5cm3 g-1 ) than UiO-66 (122.9cm3 g-1 ) at P/P0 =1. And, the HNO3 yield of Mo72 Fe30 @UiO-66 is 702.4µgg-1 h-1 , ≈7times and 24 times higher than UiO-66 and Mo72 Fe30 . This work provides reliable value for the storage and relaying artificial N2 fixation.

Kinematics of the Local Spiral Structure Revealed by Young Stars in Gaia DR3

Using young open clusters and O–B2-type stars in Gaia Data Release 3, we investigate the kinematics of the local spiral structure. In general, the young sources in the outer spiral arms may present larger peculiar motions than those in the inner spiral arms. The young open clusters appear to have smaller peculiar motions than the O–B2-type stars, and the sources in both the Perseus and Local Arms may show an inward motion toward the Galactic center and rotate slower than Galactic rotation. Meanwhile, the sources in the Carina Arm may move in the opposite direction from the Sun to the Galactic center and rotate marginally faster than Galactic rotation. In addition, using young open clusters and O–B2-type stars, we have improved the distance estimations of kinematic methods for several regions near the Sun.

A Scattered Star Group in the Orion A Region of the Milky Way

Using Gaia DR3 data, we identified an extended a ~60 pc group of stars sharing common motion but scattered in space, including from 150 to 300 probable members, named Group V. It can be associated with a group identified by Getman et al. (2019) and by Jerabkova et al. (2019) as a relic of a gas filament, traced by the mutual position of stars after the gas is swept out. We estimate its age to be approximately 16 million years. A combination of methods is applied to select probable members of Group V. We discuss the kinematic characteristics of the stars of Group V and the controversial clues they provide for understanding its nature. Due to the vicinity of a number of open clusters in the space, differentiating between members of the group and of the clusters is problematic, and mutual contamination is inevitable. The pair of clusters Gulliver 6 and UBC 17b is wrapped inside Group V but differs from it in kinematics.

The Unified Cluster Catalogue: towards a comprehensive and homogeneous data base of stellar clusters

ABSTRACT We introduce the Unified Cluster Catalogue, the largest catalogue of stellar clusters currently listing nearly 14 000 objects. In this initial release, it exclusively contains Milky Way open clusters, with plans to include other objects in future updates. Each cluster is processed using a novel probability membership algorithm, which incorporates the coordinates, parallax, proper motions, and their associated uncertainties for each star into the probability assignment process. We employ Gaia Data Release 3 (DR3) up to a G magnitude of 20, resulting in the identification of over a million probable members. The catalogue is accompanied by a publicly accessible website designed to simplify the search and data exploration of stellar clusters. The website can be accessed at https://ucc.ar.