- ID:
- ivo://CDS.VizieR/J/AJ/125/1383
- Title:
- Stromgren photometry of NGC 6253
- Short Name:
- J/AJ/125/1383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry on the intermediate-band uvbyCaH system is presented for the old open cluster NGC 6253. Despite a high level of field star contamination because of its location toward the Galactic center, combination of the data from the multiple color indices with the core cluster sample derived from radial star counts leads to the identification of a set of highly probable, single cluster members.
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- ID:
- ivo://CDS.VizieR/J/AJ/131/461
- Title:
- Stromgren photometry of NGC 2420
- Short Name:
- J/AJ/131/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry on the intermediate-band vbyCaH{beta} system is presented for the metal-deficient open cluster NGC 2420. Restricting the data to probable single members of the cluster using the CMD and the photometric indices alone generates a sample of 106 stars at the cluster turnoff.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A59
- Title:
- Structural parameters of 389 local open clusters
- Short Name:
- J/A+A/659/A59
- Date:
- 07 Mar 2022 05:56:37
- Publisher:
- CDS
- Description:
- The distribution of member stars in the surroundings of an Open Cluster (OC) can shed light on the process of its formation, evolution and dissolution. The analysis of structural parameters of OCs as a function of their age and position in the Galaxy brings constraints on theoretical models of cluster evolution. The Gaia catalogue is very appropriate to find members of OCs at large distance from their centers. We aim at revisiting the membership lists of OCs from the solar vicinity, in particular by extending these membership lists to the peripheral areas thanks to Gaia EDR3. We then take advantage of these new lists of members to study the morphological properties and the mass segregation levels of the clusters. We used the clustering algorithm HDBSCAN on Gaia parallaxes and proper motions to systematically look for members up to 50pc from the cluster centers. We fitted a King's function on the radial density profile of these clusters and a Gaussian Mixture Model (GMM) on their two dimensional distribution of members to study their shape. We also evaluated the degree of mass segregation of the clusters and the correlations of these parameters with the age and Galactic position of the clusters. Our methodology performs well on 389 clusters out of the 467 selected ones, including several recently discovered clusters that were poorly studied until now. We report the detection of vast coronae around almost all the clusters and report the detection of 71 OCs with tidal tails, multiplying by more than four the number of such structures identified. We find the size of the cores to be on average smaller for old clusters than for young ones. Also, the overall size of the clusters seems to slightly increase with age while the fraction of stars in the halo seems to decrease. As expected the mass segregation is more pronounced in the oldest clusters but a clear trend with age is not seen. OCs are more extended than previously expected, regardless of their age. The decrease in the proportion of stars populating the clusters halos highlights the different cluster evaporation processes and the short timescales they need to affect the clusters. Reported parameters like cluster sizes or mass segregation levels all depend on cluster ages but can not be described as single functions of time.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A137
- Title:
- Structure and kinematics of the Taurus region
- Short Name:
- J/A+A/630/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We take advantage of the second data release of the Gaia space mission and the state-of-the-art astrometry delivered from very long baseline interferometry observations to revisit the structure and kinematics of the nearby Taurus star-forming region. We apply a hierarchical clustering algorithm for partitioning the stars in our sample into groups (i.e., clusters) that are associated with the various molecular clouds of the complex, and derive the distance and spatial velocity of individual stars and their corresponding molecular clouds. We show that the molecular clouds are located at different distances and confirm the existence of important depth effects in this region reported in previous studies. For example, we find that the L~1495 molecular cloud is located at d=129.9^+0.4^_-0.3_pc, while the filamentary structure connected to it (in the plane of the sky) is at d=160.0^+1.2^_-1.2_pc. We report B215 and L1558 as the closest (d=128.5^+1.6^_-1.6_pc) and most remote (d=198.1^+2.5^_-2.5_pc) substructures of the complex, respectively. The median inter-cloud distance is 25pc and the relative motion of the subgroups is on the order of a few km/s. We find no clear evidence for expansion (or contraction) of the Taurus complex, but signs of the potential effects of a global rotation. Finally, we compare the radial velocity of the stars with the velocity of the underlying ^13^CO molecular gas and report a mean difference of 0.04+/-0.12km/s (with r.m.s. of 0.63km/s) confirming that the stars and the gas are tightly coupled.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/L50
- Title:
- Structure of the Upper Scorpius association
- Short Name:
- J/MNRAS/477/L50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new proper motion data from recently published catalogs, we revisit the membership of previously identified members of the Upper Scorpius association. We confirmed 750 of them as cluster members based on the convergent point method, compute their kinematic parallaxes and combined them with Gaia parallaxes to investigate the 3D structure and geometry of the association using a robust covariance method. We find a mean distance of 146+/-3+/-6pc and show that the morphology of the association defined by the brightest (and most massive) stars yields a prolate ellipsoid with dimensions of 74x38x32pc^3^, while the faintest cluster members define a more elongated structure with dimensions of 98x24x18pc^3^. We suggest that the different properties of both populations is an imprint of the star formation history in this region.
- ID:
- ivo://CDS.VizieR/J/ApJ/610/1064
- Title:
- Substellar population of lambda Ori
- Short Name:
- J/ApJ/610/1064
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By collecting optical and infrared photometry and low-resolution spectroscopy, we have identified a large number of low-mass stars and brown dwarf candidates belonging to the young cluster (~5Myr) associated with the binary star {lambda} Orionis. The lowest mass object found is an M8.5 with an estimated mass of 0.02M_{Sun}_ (~0.01M_{Sun}_ for objects without spectroscopic confirmation). For those objects with spectroscopy, the measured strength of the H{alpha} emission line follows a distribution similar to other clusters with the same age range, with larger equivalent widths for cooler spectral types.
- ID:
- ivo://CDS.VizieR/J/AJ/158/35
- Title:
- Swift UVOT Stars Survey. III. Galactic open clusters
- Short Name:
- J/AJ/158/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Swift/Ultraviolet-Optical Telescope Stars Survey, we present near-ultraviolet (NUV; 3000-1700 {AA}) point-source photometry for 103 Galactic open clusters. These data, taken over the span of the mission, provide a unique and unprecedented set of NUV point-source photometry on simple stellar populations. After applying a membership analysis fueled mostly by Gaia DR2 (Cat. I/345) proper motions, we find that 49 of these 103 have clear precise color-magnitude diagrams (CMDs) amenable to investigation. We compare the CMDs to theoretical isochrones and find good agreement between the theoretical isochrones and the CMDs. The exceptions are the fainter parts of the main sequence and the red giant branch in the uvw2-uvw1 CMDs, which is most likely due to either the difficulty of correcting for the red leak in the uvw2 filter or limitations in our understanding of UV opacities for cool stars. For the most part, our derived cluster parameters - age, distance, and reddening - agree with the consensus literature, but we find a few clusters that warrant substantial revision from literature values, notably NGC 2304, NGC 2343, NGC 2360, NGC 2396, NGC 2428, NGC 2509, NGC 2533, NGC 2571, NGC 2818, Collinder 220, and NGC 6939. A number of these are clusters in the third Galactic quadrant, where previous studies may have mistaken the disk sequence for the cluster. However, the Gaia DR2 proper motions clearly favor a different sequence. A number of clusters also show white dwarf and blue straggler sequences. We confirm the presence of extended main-sequence turnoffs in NGC 2360 and NGC 2818 and show hints of them in a number of other clusters that may warrant future spectroscopic study. Most of the clusters in the study have low extinction, and the rest are well fit by a "Milky Way-like" extinction law. However, Collinder 220 hints at a possible "LMC-like" extinction law. We finally provide a comprehensive point-source catalog to the community as a tool for future investigation.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A132
- Title:
- Teff and L for stars in 7 open clusters
- Short Name:
- J/A+A/566/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To study the time evolution of magnetic fields, chemical abundance peculiarities, and other characteristics of magnetic Ap and Bp stars during their main sequence lives, a sample of these stars in open clusters has been obtained, as such stars can be assumed to have the same ages as the clusters to which they belong. However, in exploring age determinations in the literature, we find a large dispersion among different age determinations, even for bright, nearby clusters. Our aim is to obtain ages that are as accurate as possible for the seven nearby open clusters {alpha} Per, Coma Ber, IC 2602, NGC 2232, NGC 2451A, NGC 2516, and NGC 6475, each of which contains at least one magnetic Ap or Bp star. Simultaneously, we test the current calibrations of T_e_ and luminosity for the Ap/Bp star members, and identify clearly blue stragglers in the clusters studied. We explore the possibility that isochrone fitting in the theoretical Hertzsprung-Russell diagram (i.e. log(L/L_{sun}_) vs. logT_e_), rather than in the conventional colour-magnitude diagram, can provide more precise and accurate cluster ages, with well-defined uncertainties.
- ID:
- ivo://CDS.VizieR/J/ApJS/159/100
- Title:
- Temperatures and Rc photometry in the Hyades
- Short Name:
- J/ApJS/159/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hyades photometry published by Mendoza (1967BOTT....4..149M) and other authors, Pinsonneault et al. (2004ApJ...600..946P) have recently concluded that Cousins V-I photometry published by Taylor & Joner (1985AJ.....90..479T, 1988AJ.....96..211T, 1996AJ....111.1338T) is not on the Cousins system. Extensive tests of the Taylor-Joner photometry and other pertinent results are therefore performed in this paper. It is found that in part, the Pinsonneault et al. conclusion rests on (1) a systematic error in Mendoza's (R-I)J photometry and (2) a small error in an approximate Johnson-to-Cousins transformation published by Bessell. For the Taylor-Joner values of (V-R)C, it is found that there are possible (though not definite) differences of several mmag with other results. However, the Taylor-Joner values of (R-I)C data are supported at the 1mmag level. Using the (R-I)C data and other published results, an (R-I)C catalog is assembled for 146 Hyades stars with spectral types earlier than about K5. For single stars with multiple contributing data, the rms errors of the catalog entries are less than 4.4 mmag. Temperatures on the Di Benedetto angular-diameter scale are also given in the catalog and are used to help update published analyses of high-dispersion values of [Fe/H] for the Hyades. The best current mean Hyades value of [Fe/H] is found to be +0.103+/-0.008dex and is essentially unchanged from its previous value. In addition to these numerical results, recommendations are made about improving attitudes and practices that are pertinent to issues like those raised by Pinsonneault et al.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A49
- Title:
- TGAS stars membership in 128 open clusters
- Short Name:
- J/A+A/615/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G~12 mag. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or UCAC4 proper motions, and TGAS parallaxes. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/MCMC technique to fit stellar isochrones to the observed 2MASS JHK magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2kpc, and cluster parameters from isochrone fitting for 26 of them located inside 1kpc from us. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.
