- 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).
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Search Results
- 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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A73
- Title:
- Color-period diagram for M48 (NGC2548)
- Short Name:
- J/A+A/583/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotation periods are increasingly being used to derive ages for cool single field stars. Such ages are based on an empirical understanding of how cool stars spin down, acquired by constructing color-period diagrams (CPDs) for a series of open clusters. Our main aims here are to construct a CPD for M48, to compare this with other clusters of similar age to check for consistency, and to derive a rotational age for M48 using gyrochronology. We monitored M48 photometrically for over 2months with AIP's STELLA.I 1.2m telescope and the WiFSIP 4K imager in Tenerife. Light curves with 3mmag precision for bright (V~14mag) stars were produced and then analysed to provide rotation periods. A cluster CPD has then been constructed. We report 62 rotation periods for cool stars in M48. The CPD displays a clear slow/I-sequence of rotating stars, similar to those seen in the 625Myr-old Hyades and 590Myr-old Praesepe clusters, and below both, confirming that M48 is younger. A similar comparison with the 250Myr-old M34 cluster shows that M48 is older and does not possess any fast/C-sequence G or early K stars like those in M34, although relatively fast rotators do seem to be present among the late-K and M stars. A more detailed comparison of the CPD with rotational evolution models shows that the cluster stars have a mean age of 450Myr, and its (rotating) stars can be individually dated to +/-117Myr (26%). Much of this uncertainty stems from intrinsic astrophysical spread in initial periods, and almost all stars are consistent with a single age of 450Myr. The gyro-age of M48 as a whole is 450+/-50Myr, in agreement with the previously determined isochrone age of 400+/-100Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/12
- Title:
- Coma Ber and a Neighbor Stellar Group tidal tails
- Short Name:
- J/ApJ/877/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of tidal structures around the intermediate-aged (~700-800Myr), nearby (~85pc) star cluster Coma Berenices. The spatial and kinematic grouping of stars is determined with the Gaia DR2 parallax and proper motion data, by a clustering analysis tool, StarGO, to map 5D parameters (X, Y, Z, {mu}_{alpha}*cos{delta}, {mu}_{delta}_) onto a 2D neural network. A leading and a trailing tails, each with an extension of ~50pc are revealed for the first time around this disrupting star cluster. The cluster members, totaling to ~115^+5^_-3_M_{sun}_, are clearly mass segregated, and exhibit a flat mass function with {alpha}~0.79+/-0.16, in the sense of dN/dm{prop.to}m^-{alpha}^, where N is the number of member stars and m is stellar mass, in the mass range of m=0.25-2.51M_{sun}_. Within the tidal radius of ~6.9pc, there are 77 member candidates with an average position, i.e., as the cluster center, of RA=186.8110{deg}, and DE=25.8112{deg}, and an average distance of 85.8pc. Additional 120 member candidates reside in the tidal structures, i.e., outnumbering those in the cluster core. The expansion of escaping members lead to an anisotropy in the velocity field of the tidal tails. Our analysis also serendipitously uncovers an adjacent stellar group, part of which has been cataloged in the literature. We identify 218 member candidates, 10 times more than previously known. This star group is some 65pc away from, and ~400Myr younger than, Coma Ber, but is already at the final stage of disruption.
- ID:
- ivo://CDS.VizieR/J/A+AS/136/307
- Title:
- Coma Berenices astrometric catalogue
- Short Name:
- J/A+AS/136/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of stellar positions and proper motions down to the 14th photographic magnitude in the area of the open cluster in Coma Berenices is compiled from data of 12 different sources. The accuracy of the proper motion data is comparable to that of the Hipparcos Catalogue (Cat. <I/239>).
- ID:
- ivo://CDS.VizieR/J/A+A/624/L11
- Title:
- Coma Berenices neighbor moving group
- Short Name:
- J/A+A/624/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a kinematically cold group of stars, located in the immediate neighborhood of the well-known star cluster Coma Berenices (Mel 111). The new group identified in tangential velocity space as measured by Gaia contains at least 177 coeval members distributed in two subgroups, and appears as a flattened structure parallel to the plane, stretching for about 50pc. More remarkably, the new group, which appears to have formed about 300Myr later than Mel 111 in a different part of the Galaxy, will share essentially the same volume with the older cluster when the centers of both groups will be at their closest in 13 Myr. This will result in the mixing of two unrelated populations with different metallicities. The phase of cohabitation for these two groups is about 20-30Myr, after which the two populations will drift apart. We estimate that temporal cohabitation of such populations is not a rare event in the disk of the Milky Way, and of the order of once per Galactic revolution. Our study also unveils the tidal tails of the Mel 111 cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2483
- Title:
- Comoving group associated with HD 141569
- Short Name:
- J/AJ/136/2483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for a young stellar moving group associated with the star HD 141569 - a nearby, isolated Herbig AeBe primary member of a 5+/-3Myr-old triple star system on the outskirts of the Sco-Cen complex. Our spectroscopic survey identified a population of 21 Li-rich, >~30Myr-old stars within 30{deg} of HD 141569 which possess similar proper motions with the star. The spatial distribution of these Li-rich stars, however, is not suggestive of a moving group associated with the HD 141569 triplet, but rather this sample appears cospatial with Upper Scorpius (US) and Upper Centaurus Lupus (UCL). We apply a modified moving cluster parallax method to compare the kinematics of these youthful stars with those of the US and UCL. Eight new potential members of US and five new potential members of UCL are identified. A substantial moving group with an identifiable nucleus within 15{deg} (~30pc) of HD 141569 is not found in this sample. Evidently, the HD 141569 system formed ~5Myr ago in relative isolation, tens of parsecs away from the recent sites of star formation in the Ophiucus-Scorpius-Centaurus region.
