- ID:
- ivo://CDS.VizieR/J/other/BASI/40.51
- Title:
- Cl* NGC 2539 CKY V3 and V4 BV light curves
- Short Name:
- J/other/BASI/40.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometric observations of the eclipsing contact binaries (EW type) V3 and V4 of the cluster NGC 2539 were made in the B and V bands using the 2m telescope at the IUCAA-Girawali Observatory in India. The light curves have been obtained and using the Wilson-Devinney code, the combined photometric solutions have been presented here. The photometric solutions have revealed that both V3 and V4 are W-type contact binary systems with mass ratios of 0.806 and 1.001 respectively. Revised orbital periods, absolute masses and radii of the components have been obtained.
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- ID:
- ivo://CDS.VizieR/J/A+A/650/A156
- Title:
- Cluster formation toward Be87/ON2. I.
- Short Name:
- J/A+A/650/A156
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies of star-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, located at different distances, overlap: the Berkeley 87 young massive cluster, the poorly known [DB2001] Cl05 embedded cluster, and the ON2 star-forming complex, which in turn is composed of several HII regions. We provide a methodology for building an exhaustive census of young objects that can consistently treat large differences in extinction and distance. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field were merged with archival data from Gaia, Chandra, Spitzer, and Herschel, and with cross-identifications from the literature. To address the incompleteness effects and selection biases that arise from the line-of-sight overlap, we adapted existing methods for extinction estimation and young object classification. We also defined the intrinsic reddening index, R_int_, a new tool for separating intrinsically red sources from those whose infrared color excess is caused by extinction. Finally, we introduce a new method for finding young stellar objects based on R_int_. We find 571 objects whose classification is related to recent or ongoing star formation. Together with other point sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further membership work. A new distance for Berkeley 87, (1673+/-17)pc, is estimated as a median of 13 spectroscopic members with accurate Gaia EDR3 parallaxes. The flexibility of our approach, especially regarding the R_int_ definition, allows overcoming photometric biases caused by large variations in extinction and distance, in order to obtain homogeneous catalogs of young sources. The multiwavelength census that results from applying our methods to the Berkeley 87 / ON2 field will serve as a basis for disentangling the overlapped populations.
243. Clusterix 2.0
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/5811
- Title:
- Clusterix 2.0
- Short Name:
- J/MNRAS/492/5811
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Clusterix 2.0 is a web-based, Virtual Observatory compliant, interactive tool for the determination of membership probabilities in stellar clusters based on proper-motion data using a fully non-parametric method. In an area occupied by a cluster, the frequency function is made up of two contributions: cluster and field stars. The tool performs an empirical determination of the frequency functions from the vector point diagram without relying on any previous assumption about their profiles. Clusterix 2.0 allows us to search the appropriate spatial areas in an interactive way until an optimal separation of the two populations is obtained. Several parameters can be adjusted to make the calculation computationally feasible without interfering with the quality of the results. The system offers the possibility to query different catalogues, such as Gaia, or upload a user's own data. The results of the membership determination can be sent via Simple Application Messaging Protocol (SAMP) to Virtual Observatory (VO) tools such as Tool for OPerations on Catalogues And Tables (TOPCAT). We apply Clusterix 2.0 to several open clusters with different properties and environments to show the capabilities of the tool: an area of five degrees radius around NGC 2682 (M67), an old, well-known cluster; a young cluster NGC 2516 with a striking elongated structure extended up to four degrees; NGC 1750 and NGC 1758, a pair of partly overlapping clusters; the area of NGC 1817, where we confirm a little-known cluster, Juchert 23; and an area with many clusters, where we disentangle two overlapping clusters situated where only one was previously known: Ruprecht 26 and the new Clusterix 1.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/996
- Title:
- Clusters and associations in SMC and LMC
- Short Name:
- J/MNRAS/403/996
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the degree of spatial correlation among extended structures in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). To this purpose, we work with subsamples characterized by different properties such as age and size, taken from the updated catalogue of Bica et al. (2008, Cat. J/MNRAS/389/678), or gathered in the present work. The structures are classified as star clusters or non-clusters (basically, nebular complexes and their stellar associations).
- ID:
- ivo://CDS.VizieR/J/A+AS/110/533
- Title:
- Clusters and field stars in LMC. I.
- Short Name:
- J/A+AS/110/533
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Johnson BV system to about V=23^m^ for the stars in six clusters and the surrounding fields in two regions of different nature in the Large Magellanic Cloud. The analysis includes estimations of loss of measured stars due to crowding effects.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/110
- Title:
- CN and CH indexes in stars of NGC 6791
- Short Name:
- J/ApJ/758/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-resolution SDSS/SEGUE spectra have been used to study the behavior of the strengths of the CN and CH molecular bands in stars at different evolutionary stages of the open cluster NGC 6791. We find a significant spread in the strengths of the CN bands, more than twice that expected from the uncertainties, although the bimodalities observed in globular clusters are not clearly observed here. This behavior is observed not only among red clump objects but also in unevolved stars such as those in the main sequence and lower red giant branch. In contrast, not all of the stars studied show significant scatter in their CH strengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/130
- Title:
- Collinder 261 Chandra sources & optical counterparts
- Short Name:
- J/ApJ/837/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of Collinder 261 (Cr261), which at an age of 7Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr261, and reaches a limiting X-ray luminosity of L_X_~4x10^29^erg/s (0.3-7keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r_h_, and we estimate that among the sources with L_X_>~10^30^erg/s, ~26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of Cr261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr261 has an approximate mass of 6500M_{sun}_, roughly the same as the old open cluster NGC6791. The X-ray emissivity of Cr261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.
- ID:
- ivo://CDS.VizieR/J/A+A/418/525
- Title:
- Collinder 232 & Trumpler 14/16 UBVRI photometry
- Short Name:
- J/A+A/418/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present and analyze new CCD UBVRI photometry down to V~21 in the region of the young open cluster Collinder 232, located in the Carina spiral arm, and discuss its relationship to Trumpler 14 and Trumpler 16, the two most prominent young open clusters located in the core of NGC 3372 (the Carina Nebula).
- ID:
- ivo://CDS.VizieR/J/A+A/536/A63
- Title:
- Collinder 69 very low mass stars and brown dwarfs
- Short Name:
- J/A+A/536/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied age dependent features in optical and near-infrared spectra of candidate members to the cluster (such as alkali lines and accretion associated indicators). In addition, we have complemented that study with the analysis of other youth indicators like X-ray emission or mid-infrared excess. We have confirmed the membership to Collinder 69 of ~90 photometric candidate members. As a byproduct we have determined a temperature scale for young M, very low-mass stars and brown dwarfs. We have assembled one of the most complete Initial Mass Functions from 0.016 to 20M_{sun}_. And, finally, we have studied the implications of the spatial distribution of the confirmed members on the proposed mechanisms of brown dwarfs formation.
- ID:
- ivo://CDS.VizieR/J/A+A/526/A21
- Title:
- Collinder 69 X-ray sources
- Short Name:
- J/A+A/526/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper of a series devoted to the {lambda} Orionis star-forming region, Orion's Head, from the X-ray perspective. Our final aim is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. We aim to uncover the population of the central, young star cluster Collinder 69, and in particular those diskless Class III objects not identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association.