Young Open Cluster Research Articles

The Radcliffe wave as traced by young open clusters. Stellar parameters, activity indicators, and abundances of solar-type members of eight young clusters

The Radcliffe wave has only recently been recognised as a approx 3\,kpc long coherent gas structure encompassing most of the star-forming regions in the solar vicinity. Since its discovery, it has been mainly studied from the perspective of dynamics, but a detailed chemical study is necessary to understand its nature and the composition of the natal clouds that gave rise to it. For this paper we used some of the connected young open clusters (age lesssim 100 Myr) as tracers of the molecular clouds. We performed high-resolution spectroscopy with GIARPS at the TNG of 53 stars that are bona fide members of seven clusters located at different positions along the Radcliffe wave. We provide radial velocities and atmospheric parameters for all of them. For a subsample consisting of 41 FGK stars, we also studied the chromospheric activity and the content of Li, from which we inferred the age of the parent clusters. These values agree with the evolutionary ages reported in the literature. For these FGK stars, we determined the chemical abundances for 25 species. Pleiades, ASCC\,16, and NGC\,7058 exhibit a solar metallicity while Melotte\,20, ASCC\,19, NGC\,2232, and Roslund\,6 show a slightly subsolar value (approx \,$-$0.1\,dex). On average, the clusters show a chemical composition compatible with that of the Sun, especially for alpha - and Fe-peak elements. Neutron-capture elements, on the other hand, present a slight overabundance of about 0.2\,dex, especially barium. Finally, considering also ASCC\,123, which was studied by our group in a previous research project, we inferred a correlation between the chemical composition and the age or position of the clusters along the wave, demonstrating their physical connection within an inhomogeneous mixing scenario.

A deep investigation of the poorly studied open cluster King 18 using CCD VRI, Gaia DR3 and 2MASS

In this paper, we re-estimate the astrometric and photometric parameters of the young open star cluster King 18 based on Gaia Data Release 3 (DR3), Two Micron All-sky Survey (2MASS) and VRI CCD observations using the f/4.9 Newtonian focus of 74-inch telescope at Kottamia Astronomical Observatory (KAO) in Egypt. King 18 is a poorly studied open star cluster, for which new results are found in the current study. In order to estimate the membership and determine all the astrophysical parameters of the cluster, we have used data from Gaia DR3 and KAO. The center, cluster radius, radial density distribution, color-magnitude diagrams, distance, age, and reddening of King 18 are calculated. Also, the luminosity and mass functions, the total mass and the relaxation time of the cluster are estimated. The slope value of the mass function (α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}) of King 18 is found to be 2.27± 0.17, which is comparable with Salpeter value. Our estimates for the average cluster age and the relaxation time are 224 ± 6.3 and 28.92 Myrs, respectively. This indicates that King 18 is dynamically stable and a relaxed cluster. The cluster distance modulus from Gaia, 2Mass and VRI observations has been determined to be 12.380 ± 1.320, 12.320 ± 0.107 and 12.280 ± 0.290 mag respectively, which corresponds to distances of 2992.26, 2910.72 and 2857.59 pc, respectively. These results are in good agreement within the error. Moreover the color excesses E(V–I), E(J–Ks\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {K}_s$$\\end{document}) and E(GBP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {G}_{{BP}}$$\\end{document}–GRP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {G}_{{RP}}$$\\end{document}) are 0.850 ± 0.087, 0.380 ± 0.091 and 0.980 ± 0.130 respectively. Finally, the proper motions (μα\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _{\\alpha }$$\\end{document}cosδ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta $$\\end{document}, μδ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _{\\delta }$$\\end{document}), and parallaxes (ϖ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varpi $$\\end{document}) are -2.603±0.018\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-2.603 \\pm 0.018$$\\end{document}, -2.106±0.013\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-2.106 \\pm 0.013$$\\end{document} and 0.324 ± 0.040, respectively.

A binary supernova OB-runaway candidate inside Berkeley 97

OB-runaway stars ejected by the binary supernova mechanism can be found near young open star clusters. In this paper, we present an OB-runaway candidate as a pre-SN binary companion to the progenitor of the pulsar PSR J2238$+$5903 inside the young open star cluster Berkeley 97. We tried to find a kinematic outlier based on Gaia DR3 proper motions and parallaxes to be the pre-supernova binary companion to the progenitor of the pulsar. We took the spectra of two bright early B-type stars of the cluster, determined their effective temperature and surface gravity, and updated the parameters of the cluster. Through isochrone fitting of the color-magnitude diagram of the star cluster, we identified the members and determined the stellar parameters of the runaway star. Two bright members of the cluster, HD 240015 and HD 240016, are massive stars with spectral types of B0.5II and B1.5II and effective temperatures of $T_ eff K and $T_ eff K, respectively, as well as surface gravities of $ g cm/s^2 We find that Berkeley 97 is a star cluster with an age of $ age yr )=7.1$, an uncertainty of $<0.1$ dex, and an interstellar extinction of $A_ V mag. The runaway star has an effective temperature of $T_ eff K with a surface gravity of $ g cm/s^2 (B8V type star). By tracing back the proper motion of the runaway star, the explosion center was found for different possible pulsar ages of 10, 20, and 26.6 kyr. The pulsar moving out from the 20 kyr position must have a space velocity of $ km $, which is consistent with the general pulsar velocity distribution. This supports the idea that the pulsar originated from the cluster as a result of a binary supernova. Despite its young age, $ kyr, the supernova remnant is not visible.

Mapping radial abundance gradients with Gaia -ESO open clusters. Evidence of recent gas accretion in the Milky Way disk

Recent evidence from spectroscopic surveys points towards the presence of a metal-poor, young stellar population in the low-alpha , chemically thin disk. In this context, the investigation of the spatial distribution and time evolution of precise, unbiased abundances is fundamental to disentangle the scenarios of formation and evolution of the Galaxy. We study the evolution of abundance gradients in the Milky Way by taking advantage of a large sample of open star clusters, which are among the best tracers for this purpose. In particular, we used data from the last release of the Gaia -ESO survey. We performed a careful selection of open cluster member stars, excluding those members that may be affected by biases in spectral analysis. We compared the cleaned open cluster sample with detailed chemical evolution models for the Milky Way, using well-tested stellar yields and prescription for radial migration. We tested different scenarios of Galaxy evolution to explain the data, namely, the two-infall and the three-infall frameworks, which suggest the chemical thin disk is formed by one or two subsequent gas accretion episodes, respectively. With the performed selection in cluster member stars, we still find a metallicity decrease between intermediate-age ($1<$ Age/Gyr $<3$) and young (Age $<1$ Gyr) open clusters. This decrease cannot be explained in the context of the two-infall scenario, even by accounting for the effect of migration and yield prescriptions. The three-infall framework, with its late gas accretion in the last 3 Gyr, is able to explain the low metallic content in young clusters. However, we have invoked a milder metal dilution for this gas infall episode relative to previous findings. To explain the observed low metallic content in young clusters, we propose that a late gas accretion episode triggering a metal dilution would have taken place, extending the framework of the three-infall model for the first time to the entire Galactic disk.

On the Origin of Fast-rotating Stars. I. Photometric Calibration and Results of AO-assisted BVRI+Hα Imaging of NGC 330 with SAMI/SOAR

Hα emission is a clear indicator of circumstellar activity in Be stars, historically employed to assess the classical Be star (CBe) population in young open clusters (YOCs). The YOC NGC 330 in the Small Magellanic Cloud exhibits a large known fraction of CBe stars and was selected for a pilot study to establish a comprehensive methodology for identifying Hα emitters in the Magellanic Clouds, encompassing the entire B-type spectral range. Using the SOAR Adaptive Module Imager (SAMI), we investigated the stellar population of NGC 330 using multiband BVRI+Hα imaging. We identified Hα emitters within the entire V-band range covered by SAMI/SOAR observations (V ≲ 22), comprising the complete B-type stellar population and offering a unique opportunity to explore the Be phenomenon across all spectral subclasses. The stellar radial distribution shows a clear bimodal pattern between the most massive (B5 or earlier) and the lower mass main-sequence objects (later than B6) within the cluster. The former is concentrated toward the cluster center (showing a dispersion of σ = 4.26 ± 0.20 pc), whereas the latter extends across larger radii (σ = 10.83 ± 0.65 pc), indicating mass stratification within NGC 330. The total fraction of emitters is 4.4% ± 0.5%, notably smaller than previous estimates from flux- or seeing-limited observations. However, a higher fraction of Hα emitters is observed among higher mass stars (32.8% ± 3.4%) than within lower mass (4.4% ± 0.9%). Consequently, the putative CBe population exhibits distinct dynamical characteristics compared to the bulk of the stellar population in NGC 330. These findings highlight the significance of the current observations in providing a complete picture of the CBe population in NGC 330.

The Destiny of the Open Cluster NGC 6530: Past and Future

Studying the structures of open clusters is crucial for understanding stellar evolution and galactic dynamics. Based on Gaia DR3 data, we apply the hierarchical clustering algorithm to the young open cluster NGC 6530 and group its members into five substructures. By linear tracing with the kinematic information of their members, we find that sub 1 is the core of the cluster. It is expanding slowly. Sub 2 consists of less-bound members, which began escaping from the core about 0.78 Myr ago. Sub 3 is associated with a young star-forming region. It will merge with the core after 0.72 Myr. Sub 4, as an outskirts group, is also moving toward the core but will not end up falling in. Sub 5 is composed of less-bound members with field contamination. This work reveals the complex internal structure and evolutionary trends of the cluster NGC 6530. It also shows the potential of the hierarchical clustering algorithm in star cluster structure analysis.

Open superclusters

We define an open supercluster (OSC) as a cluster of at least six open clusters (OCs) born from the same giant molecular cloud (GMC). We surveyed the recent catalogs of OCs based on Gaia data and relevant literature to find 17 OSCs of the third Galactic quadrant, along with 190 likely members of them. OSCs are frequent enough to be considered an extra class of objects in the hierarchy of star formation. Some of these supersystems are new and most of them contain more members than previously thought. The detailed study of some OSCs lead to the discovery of four new young OCs that are members of them, named Casado-Hendy 2–5. In certain instances, subgroups with distinct proper motions (PMs) or 3D positions have been found within an OSC, suggesting the presence of multiple generations of stars formed from several bursts of star formation within the same GMC. OSCs are typically unbound and tend to disintegrate on timescales of ∼0.1 Gyr. The present results confirm that young OCs tend to form primordial groups and suggest that globular clusters (GCs) are not formed from the accretion of OSCs, that is, at least in the local Universe at late times.

Evolution of Stellar Rotation in Open Clusters

Understanding stellar rotation and the role of magnetic braking remains a major outstanding problem in astrophysics. In this paper, stellar rotation of the young open cluster Blanco 1 is investigated and compared with other clusters with ages ranging from ∼35 Myr to ∼950 Myr and star masses in the range 0.2 < M⊙ < 1.4. It is proposed that rotation rates of stars in young open clusters are determined by the early angular momentum acquired during formation and not by magnetic braking effects, which operate on longer time scales. On the convective C Sequence, for lighter stars, the early angular velocity is related directly to the moment of inertia. However, for the interface or I Sequence, differential rotation exists and observed rotation rates are essentially the rotation rates of the outer convection zone. It is estimated that the convection zone can rotate at over 10× the rate of the inner radiative zone for heavier stars. This differential rotation process can drive saturated interface dynamos that lead to large rotational mass dependences which can be described by a simple energy transfer model. Comparing with clusters of different ages magnetic braking outlines the evolution of older clusters from young clusters. For old clusters such as Praesepe the majority of stars have experienced spin down, that can be described by a simple model based on an additional momentum loss proportional to the angular momentum of the early cluster, which for the I Sequence is consistent with the well known Skumanich relation.

Gaia DR3 Data of Very Young Open Cluster NGC 6530: Distance and Evolutionary Stage of Selected Stars

Gaia EDR3 and Gaia DR3 data of selected stars in the very young (1.5 million years old) open cluster NGC 6530 are presented. All the selected stars have very accurate Gaia DR3 distances. Most of the selected stars are very young B stars and several of them are young stellar objects. From the analysis of selected stars, the distance to NGC 6530 is found to be 1318 pc. The two very red stars VAJ 304 and 338 have little bit less proper motion than other members of the NGC 6530 and their Mv values are found to be −3.57 and −3.68 respectively. They are much brighter than K5 III RGB stars and less luminous than massive K5 red supergiants. It is likely VAJ 304 and VAJ 338 are not members of NGC 6530 they may be field K5 type AGB or post-AGB stars. Further study of these two stars is needed.

Mass and wind luminosity of young Galactic open clusters in Gaia DR2

Context. Star clusters constitute a significant part of the stellar population in our Galaxy. The feedback processes they exert on the interstellar medium impact multiple physical processes from the chemical to the dynamical evolution of the Galaxy. In addition, young and massive stellar clusters might act as efficient particle accelerators and contribute to the production of cosmic rays. Aims. We aim at evaluating the wind luminosity driven by the young (< 30 Myr) Galactic open stellar clusters observed by the Gaia space mission. This is crucial for determining the energy channeled into accelerated particles. Methods. To do this, we developed a method relying on the number, magnitude, and line-of-sight extinction of the stars observed per cluster. Assuming that the stellar mass function follows a Kroupa mass distribution and accounting for the maximum stellar mass allowed by the age and mass of the parent cluster, we conservatively estimated the mass and wind luminosity of 387 local clusters within the second data release of Gaia. Results. We compared the results of our computation with recent estimates of young cluster masses. With respect to these, our sample is three times more abundant, particularly above a few thousand solar masses. This is of the utmost relevance for predicting the gamma-ray emission resulting from the interaction of accelerated particles. The cluster wind luminosity distribution we obtained extends up to 3 × 1038 erg s−1. This is a promising feature in terms of potential particle acceleration scenarios.

Boron Abundances in Early B Dwarfs of the Galactic Open Cluster NGC 3293* * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal GO-14673.

New boron abundances or upper limits have been determined for eight early B stars in the young Galactic open cluster NGC 3293, using UV spectra obtained by the Hubble Space Telescope Cosmic Origins Spectrograph. With previous observations, there are now 18 early B stars in this cluster with boron measurements. Six of the newly observed stars have projected rotational velocities greater than 200 km s−1, allowing new constraints on rotationally driven mixing in main-sequence stars. When comparing to synthetic model populations, we find that the majority of our sample stars agree well with the predicted trends of stronger boron depletion for larger rotation and for larger mass or luminosity. Based on those, a smaller than the canonical rotational mixing efficiency (f c ≈ 0.0165 versus the more standard value of 0.033) appears to be favored. In addition, the five mostly slowly rotating stars, when considered as a group, tend to show more boron depletion than expected from rotational mixing, and we speculate that most or all of these originate from binary mergers.

Asteroseismology of the young open cluster NGC 2516

Context. Asteroseismic modelling of isolated stars presents significant challenges due to the difficulty in accurately determining stellar parameters, particularly the stellar age. These challenges can be overcome by observing stars in open clusters whose coeval members share an initial chemical composition. The light curves from the all-sky survey by the Transiting Exoplanet Survey Satellite (TESS) allow us to investigate and analyse stellar variations in clusters with an unprecedented level of detail for the first time. Aims. We aim to detect gravity-mode oscillations in the early-type main-sequence members of the young open cluster NGC 2516 to deduce their internal rotation rates. Methods. We selected the 301 member stars with no more than mild contamination as our sample. We analysed the full-frame image light curves, which provide nearly continuous observations in the first and third years of TESS monitoring. We also collected high-resolution spectra using the Fiber-fed Extended Range Optical Spectrograph for the g-mode pulsators, with the aim of assessing the Gaia effective temperatures and gravities and preparing for future seismic modelling. Results. By fitting the theoretical isochrones to the colour-magnitude diagram of a cluster, we determined an age of 102 ± 15 Myr and inferred that the extinction at 550 nm (A0) is 0.53 ± 0.04 mag. We identified 147 stars with surface-brightness modulations: 24 with gravity (g-)mode pulsations (γ Doradus or slowly pulsating B-type stars) and 35 with pressure (p-)mode pulsations (δ Sct stars). When sorted by colour index, the amplitude spectra of the δ Sct stars show a distinct ordering and reveal a discernible frequency-temperature relationship. The near-core rotation rates, measured from period spacing patterns in two slowly pulsating B-type (SPB) stars and nine γ Dor stars, reach up to 3 d−1. This is at the high end of the values found from Kepler data of field stars of similar variability type. The γ Dor stars of NGC 2516 have internal rotation rates as high as 50% of their critical value, whereas the SPB stars exhibit rotation rates close to their critical rate. Although the B-type stars are rotating rapidly, we did not find long-term brightness and colour variations in the mid-infrared, which suggests that there are no disc or shell formation events in our sample. We also discussed the results of our spectroscopic observations for the g-mode pulsators.

Study of 26 Galactic Open Clusters with Extended Main-sequence Turnoffs

Recent studies indicate that some Galactic open clusters (OCs) exhibit extended main-sequence turnoff (eMSTO) in their color–magnitude diagrams (CMDs). However, the number of Galactic OCs with eMSTO structures detected so far is limited, and the reasons for their formation are still unclear. This work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these features. Stellar population types and fundamental parameters of cluster samples are acquired using CMD fitting methods. Among them, the results of 11 OCs are reliable as the observed CMDs are well-reproduced. We propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO morphologies. The results also show that the impact of age spread is important, as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.

Exploring NGC 2345: A Comprehensive Study of a Young Open Cluster through Photometric and Kinematic Analysis

We conducted a photometric and kinematic analysis of the young open cluster NGC 2345 using CCD UBV data from 2 m Himalayan Chandra Telescope, Gaia Data Release 3, Two Micron All-Sky Survey, and the Photometric All-Sky Survey data sets. We found 1732 most probable cluster members with membership probability higher than 70%. The fundamental and structural parameters of the cluster are determined based on the cluster members. The mean proper motion of the cluster is estimated to be μαcosδ = −1.34 ± 0.20 and μ δ = 1.35 ± 0.21 mas yr−1. Based on the radial density profile, the estimated radius is ∼12.′8 (10.37 pc). Using color–color and color–magnitude diagrams, we estimate the reddening, age, and distance to be 0.63 ± 0.04 mag, 63 ± 8 Myr, and 2.78 ± 0.78 kpc, respectively. The mass function slope for main-sequence stars is determined as 1.2 ± 0.1. The mass function slope in the core, halo, and overall region indicates a possible hint of mass segregation. The cluster’s dynamical relaxation time is 177.6 Myr, meaning ongoing mass segregation, with complete equilibrium expected in 100–110 Myr. Apex coordinates are determined as −40.°89 ± 0.12, − 44.°99 ± 0.15. The cluster’s orbit in the Galaxy suggests early dissociation into field stars due to its close proximity to the Galactic disk.

The first CCD photometric studies of the member eclipsing binary ZTFJ015003.88+534734.1 in the newly discovered young open cluster UBC 188

We present the first CCD observations of an eclipsing binary, ZTFJ015003.88+534734.1, which is a member in the open star cluster UBC 188. The observations were taken by the 1.88 m telescope at the Kottamia Astronomical Observatory (KAO) in SDSS griz bands. The latest version of the Wilson-Devinney (W-D) code was employed for photometric analysis and light curve modeling of the eclipsing binary. The results indicate that the binary system is in an over-contact configuration. The mass of the primary star (M1) is determined to be 1.293 M⊙, and the mass of the secondary star (M2) is directly derived from the system's estimated mass ratio (q = M2/M1) as 0.340 times the solar mass (M⊙). We investigated the color-magnitude diagram and the membership probability of the open cluster UBC 188 using the Gaia DR3 data. We determined the membership probability of the eclipsing binary ZTFJ015003.88+534734.1 using the pyUPMASK algorithm and found that its membership probability is one.

High-resolution spectroscopy of the young open cluster M 39 (NGC 7092)

M 39 is a nearby young open cluster hardly studied in the last few decades. No giant is known among its members and its chemical composition has never been studied. In order to investigate it, we performed high-resolution spectroscopy of 20 expected cluster members with the HARPS and FIES spectrographs. By combining our observations with archival photometry and Gaia-DR3 data we searched for evolved members and studied cluster properties such as the radial velocity, extinction, and age. For the first time, we provide stellar parameters and chemical abundances for 21 species with atomic numbers up to 56. We have not found any new giant as a likely member and we notice a negligible reddening along the cluster field, which we place at 300 pc. We obtain a mean radial velocity for M 39 of −5.5 ± 0.5 km s−1 and an isochrone-fitting age of 430 ± 110 Ma, which corresponds to a MSTO mass of around 2.8 M⊙. This value is consistent with the Li content and chromospheric activity shown by its members. Based on main-sequence stars, the cluster exhibits a solar composition, [Fe/H] = +0.04 ± 0.08 dex, compatible with its Galactocentric location. However, it has a slightly subsolar abundance of Na and an enriched content of neutron-capture elements, specially Ba. In any case, the chemical composition of M 39 is fully compatible with that shown by other open clusters that populate the Galactic thin disc.

A statistical and multiwavelength photometric analysis of a young embedded open star cluster: IC 1590

ABSTRACT We present a statistical and multiwavelength photometric studies of young open cluster IC 1590. We identified 91 cluster members using Gaia DR3 astrometry data using ensemble-based unsupervised machine learning techniques. From Gaia EDR3 data, we estimate the best-fitting parameters for IC 1590 using the Automated Stellar Cluster Analysis package (asteca) yielding the distance d ∼ 2.87 ± 0.02 kpc, age ∼ 3.54 ± 0.05 Myr, metallicity z ∼ 0.0212 ± 0.003, binarity value of ∼ 0.558, and extinction Av ∼ 1.252 ± 0.4 mag for an Rv value of ∼ 3.322 ± 0.23. We estimate the initial mass function slope of the cluster to be α = 1.081 ± 0.112 for single stars and α = 1.490 ± 0.051 for a binary fraction of ∼ 0.558 in the mass range 1 M⊙ ≤ m (M⊙) ≤ 100 M⊙. The G-band luminosity function slope is estimated to be ∼ 0.33 ± 0.09. We use (J − H) versus (H − Ks) colour–colour diagram to identify young stellar objects (YSOs). We found that all the identified YSOs have ages ≤ 2 Myr and masses ∼ 0.35 – 5.5 M⊙. We also fit the radial surface density profile. Using the galpy, we performed orbit analysis of the cluster. The extinction map for the cluster region has been generated using the PNICER technique, and it is almost similar to the dust structure obtained from the 500 μm dust continuum emissions map of Herschel SPIRE. We finally at the end discussed the star formation scenario in the cluster region.

Tracing the Origins of Mass Segregation in M35: Evidence for Primordially Segregated Binaries

M35 is a young open cluster and home to an extensive binary population. Using Gaia Data Release 3, Pan-STARRS, and Two Micron All Sky Survey photometry with the Bayesian statistical software, BASE-9, we derive precise cluster parameters, identify single and binary cluster members, and extract their masses. We identify 571 binaries down to Gaia G = 20.3 and a lower limit on the binary frequency of f b = 0.41 ± 0.02. We extend the binary demographics by many magnitudes faint-ward of previous (radial-velocity) studies of this cluster and further away from the cluster center (1.°78, roughly 10 core radii). We find the binary stars to be more centrally concentrated than the single stars in the cluster. Furthermore, we find strong evidence for mass segregation within the binary population itself, with progressively more-massive binary samples becoming more and more centrally concentrated. For the single stars, we find weaker evidence for mass segregation; only the most massive single stars (>2.5M ⊙) appear more centrally concentrated. Given the cluster age of ∼200 Myr, and our derived half-mass relaxation time for the cluster of 230 ± 84 Myr, we estimate ∼47% of the binary stars and ∼12% of single stars in the cluster have had time to become dynamically mass segregated. Importantly, when we investigate only stars with mass segregation timescales greater than the cluster age, we still find the binaries to be more centrally concentrated than the singles, suggesting the binaries may have formed with a primordially different spatial distribution from that of the single stars.

Constraining Stellar Rotation at the Zero-age Main Sequence with TESS

The zero-age main sequence (ZAMS) is a critical phase for stellar angular momentum evolution, as stars transition from contraction-dominated spin-up to magnetic wind-dominated spin-down. We present the first robust observational constraints on rotation for FGK stars at ≈40 Myr. We have analyzed TESS light curves for 1410 members of five young open clusters with ages between 25 and 55 Myr: IC 2391, IC 2602, NGC 2451A, NGC 2547, and Collinder 135. In total, we measure 868 rotation periods, including 96 new, high-quality periods for stars around 1 M ⊙. This is an increase of ten times the existing literature sample at the ZAMS. We then use the τ 2 method to compare our data to models for stellar angular momentum evolution. Although the ages derived from these rotation models do not match isochronal ages, we show that these observations can clearly discriminate between different models for stellar wind torques. Finally, τ 2 fits indicate that magnetic braking and/or internal angular momentum transport significantly impact rotational evolution even on the pre-main sequence.

Age-dating the young open cluster UBC 1 with g-mode asteroseismology, gyrochronology, and isochrone fitting

Aims. UBC 1 is an open cluster discovered in Gaia data and located near the edge of the Transiting Exoplanet Survey Satellite’s (TESS) continuous viewing zone. We aim to provide age constraints for this poorly studied open cluster from the combination of gravity-mode (g-mode) asteroseismology, gyrochronology, and isochrone fitting. Methods. We established the members of UBC 1 from a spatial-kinematic filtering and estimate the cluster age and its parameters. Firstly, we fitted rotating isochrones to the single star cluster sequence. Secondly, using TESS time-series photometry, we explored the variability of the upper main sequence members and identified potential g-mode pulsators. For one star, we found a clear period spacing pattern that we used to deduce the buoyancy travel time, the near-core rotation rate, and an asteroseismic age. For a third independent age estimate, we employed the rotation periods of low-mass members of UBC 1. Results. Based on isochrone fitting, we find log t = 8.1 ± 0.4, where the large uncertainty occurs because UBC 1 does not host evolved stars. From asteroseismology of one g-mode pulsator, we find a constrained age of log t = 8.24−0.14+0.43. From gyrochronology based on 17 cool star cluster members, we estimate log t = 8.35−0.25+0.16. Combined, all three methods lead to a consistent age in the range of 150 − 300 Myr. Conclusions. Our results show that even a single cluster member with identified g modes can improve age-dating of young open clusters. Combining the gyrochronology of low-mass members with asteroseismology of intermediate-mass members is a powerful tool for young open cluster modelling, including high-precision age-dating.