- ID:
- ivo://CDS.VizieR/J/A+A/516/A3
- Title:
- Proper motions of PM2000 open clusters
- Short Name:
- J/A+A/516/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present lists of proper-motions and kinematic membership probabilities in the region of 49 open clusters or possible open clusters. The stellar proper motions were taken from the Bordeaux PM2000 catalogue. The segregation between cluster and field stars and the assignment of membership probabilities was accomplished by applying a fully automated method based on parametrisations for the probability distribution functions and genetic algorithm optimisation heuristics associated with a derivative-based hill climbing algorithm for the likelihood optimization.
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- ID:
- ivo://CDS.VizieR/J/A+AS/118/503
- Title:
- Proper motions of stars in Ori Nebula
- Short Name:
- J/A+AS/118/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Relative proper motions and membership probabilities for 333 stars within an area of 1.6deg by 1.8deg centred on the Orion Nebula M 42 are determined using plates taken over a period of 83 years with the double astrograph of Shanghai Observatory (scale of 30"/mm). The plates were measured with the ASTROSCAN automatic plate-measuring machine of Leiden Observatory. The average proper motion accuracy obtained for stars in the photographic magnitude range 7 to 14 is 0.3mas/yr. Errors are somewhat larger towards fainter and brighter magnitude, but the majority lie well below 1mas/yr. 64% of the stars have been measured successfully on at least 13 out of 18 plates. The number of stars with membership probabilities higher than 0.7 is 184. It is shown by a detailed discussion that the proper motions and membership probabilities of the stars determined in this paper are in good agreement with the results presented recently by other authors. Although there is a clear concentration in the proper motion diagram, both the remaining dispersion of the internal motions and the distribution of "members" as projected on the sky indicate that the stars in this region are not bound as one system, but do have a common origin. A similar conclusion can be drawn from a comparison with spectroscopic and radial velocity data.
- ID:
- ivo://CDS.VizieR/J/AJ/144/158
- Title:
- Properties of B and Be stars in h and {chi} Persei
- Short Name:
- J/AJ/144/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the B and Be star populations of the double cluster h and {chi} Persei. Blue optical spectroscopy is used to first measure projected rotational velocity, vsini, effective surface temperature, T_eff_, and surface gravity, logg, for B-type sample stars, while available Stromgren photometry is used to calculate T_eff_ and logg for the Be stars showing emission. In our sample of 104 objects for which we measured these stellar parameters, 28 are known or proposed Be stars. Of these Be stars, 22 show evidence of emission at the times of our observations, and furthermore, we find evidence in our data and the literature for at least 8 transient Be stars in the clusters. We find that the Be stars are not rotating near their critical velocity, contrary to the results of studies of similar open clusters. We compare the results of our analysis with other previous studies and find that the cluster members are more evolved than found by Huang & Gies but still retain much of their initial rotational angular momentum.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A80
- Title:
- Properties of Collinder 69 low-mass members
- Short Name:
- J/A+A/547/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most observational studies conducted so far point toward brown dwarfs sharing a similar formation mechanism as the one that is accepted for low-mass stars. However, larger databases and more systematic studies are needed before strong conclusions can be reached. In this second paper of a series devoted to studying the spectroscopic properties of the Lambda Orionis star-forming region members, we study accretion, activity and rotation for a wide set of spectroscopically confirmed members of the central star cluster Collinder 69 to assess analogies and/or differences between the brown-dwarf and stellar populations of this cluster. Moreover, we present comparisons with other star-forming regions of similar and different ages to address environmental effects on our conclusions. We studied prominent photospheric lines to derive rotational velocities and emission lines to distinguish between accretion processes and chromospheric activity. In addition, we include information about disk presence and X-ray emission.
- ID:
- ivo://CDS.VizieR/J/AJ/134/411
- Title:
- Properties of IC 348 members
- Short Name:
- J/AJ/134/411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spitzer mid-infrared surveys enable an accurate census of young stellar objects by sampling large spatial scales, revealing very embedded protostars, and detecting low-luminosity objects. Taking advantage of these capabilities, we present a Spitzer-based census of the IC 348 nebula and embedded star cluster, covering a 2.5pc region and comparable in extent to the Orion Nebula. Our Spitzer census supplemented with ground-based spectra has added 42 Class II T Tauri sources to the cluster membership and identified ~20 Class 0/I protostars. The population of IC 348 likely exceeds 400 sources after accounting statistically for unidentified diskless members. Our Spitzer census of IC 348 reveals a population of Class I protostars that is anticorrelated spatially with the Class II/III T Tauri members, which comprise the centrally condensed cluster around a B star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/499/4114
- Title:
- Properties of LMC star clusters
- Short Name:
- J/MNRAS/499/4114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The YMCA (Yes, Magellanic Clouds Again) and STEP (The SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) projects are deep g, i photometric surveys carried out with the VLT Survey Telescope (VST) and devoted to study the outskirts of the Magellanic System. A main goal of YMCA and STEP is to identify candidate stellar clusters and complete their census out to the outermost regions of the Magellanic Clouds. We adopted a specific overdensity search technique coupled with a visual inspection of the colour-magnitude diagrams to select the best candidates and estimate their ages. To date, we analysed a region of 23 square degrees in the outskirts of the Large Magellanic Cloud, detecting 85 candidate cluster candidates, 16 of which have estimated ages falling in the so-called age gap. We use these objects together with literature data to gain insight into the formation and interaction history of the Magellanic Clouds.
- ID:
- ivo://CDS.VizieR/J/AJ/155/44
- Title:
- Properties of PMS stars in young cluster Berkeley 59
- Short Name:
- J/AJ/155/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Berkeley 59 is a nearby (~1 kpc) young cluster associated with the Sh2-171 H II region. We present deep optical observations of the central ~2.5x2.5 pc^2^ area of the cluster, obtained with the 3.58 m Telescopio Nazionale Galileo. The V/(V-I) color-magnitude diagram manifests a clear pre-main-sequence (PMS) population down to ~0.2 M_{sun}_. Using the near-infrared and optical colors of the low-mass PMS members, we derive a global extinction of A_V_=4 mag and a mean age of ~1.8 Myr, respectively, for the cluster. We constructed the initial mass function and found that its global slopes in the mass ranges of 0.2-28 M_{sun}_ and 0.2-1.5 M_{sun}_ are -1.33 and -1.23, respectively, in good agreement with the Salpeter value in the solar neighborhood. We looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. The dynamical status of the cluster suggests that the mass segregation is likely primordial. The age distribution of the PMS sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star-forming clouds. Within the observed area, we derive a total mass of ~10^3^ M_{sun}_ for the cluster. Comparing the properties of Berkeley 59 with other young clusters, we suggest it resembles more closely the Trapezium cluster.
- ID:
- ivo://CDS.VizieR/J/other/ApSS/344.175
- Title:
- Protoclusters and subclusters
- Short Name:
- J/other/ApSS/344
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A hybrid JHKs - W1W2W3W4 high-spectral index ({alpha}) selection scheme was employed to identify (sub)clusters of class I/f candidate protostars (YSOs) in WISE observations (the Wide-Field Infrared Survey Explorer). n>10^4^ candidate YSOs were detected owing to WISE's advantageous all-sky spatial coverage, and a subsample (n~200) of their heavily-obscured host (sub)clusters were correlated with the Avedisova (2002, Cat. V/112) and Dias et al. (2002A&A...389..871D, Cat. B/ocl) catalogs of star-forming regions. Forthcoming observations from the VVV/UKIDSS surveys shall facilitate the detection of additional protostars and bolster efforts to delineate the Galactic plane, since the campaigns aim to secure deep JHKs photometry for a pertinent fraction of the WISE targets lacking 2MASS detections, and to provide improved data for YSOs near the limits of the 2MASS survey.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A132
- Title:
- Pseudo-photometric distances of 30 open clusters
- Short Name:
- J/A+A/619/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We demonstrate that reliable photometric distances of stellar clusters, and more generally of stars, can be obtained using pseudomagnitudes and rough spectral type without having to correct for visual absorption. We determine the mean absolute pseudomagnitude of all spectral (sub)types between B and K. Distances are computed from the difference between the star's observed pseudomagnitude and its spectral type's absolute pseudomagnitude. We compare the distances of 30 open clusters thus derived against the distances derived from TGAS parallaxes. Our computed distances, up to distance modulus 12, agree within 0.1mag rms with those obtained from TGAS parallaxes, proving excellent distance estimates. We show additionally that there are actually two markedly different distances in the cluster NGC 2264. We suggest that the pseudomagnitude distance estimation method, which is easy to perform, can be routinely used in all large-scale surveys where statistical distances on a set of stars, such as an open cluster, are required.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/81
- Title:
- PTF stellar rotation periods for Pleiades members
- Short Name:
- J/ApJ/822/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation periods (P_rot_) measured in open clusters have proved to be extremely useful for studying stars' angular momentum content and rotationally driven magnetic activity, which are both age- and mass-dependent processes. While P_rot_ measurements have been obtained for hundreds of solar-mass members of the Pleiades, measurements exist for only a few low-mass (<0.5 M_{sun}_) members of this key laboratory for stellar evolution theory. To fill this gap, we report P_rot_ for 132 low-mass Pleiades members (including nearly 100 with M=<0.45 M_{sun}_), measured from photometric monitoring of the cluster conducted by the Palomar Transient Factory in late 2011 and early 2012. These periods extend the portrait of stellar rotation at 125 Myr to the lowest-mass stars and re-establish the Pleiades as a key benchmark for models of the transport and evolution of stellar angular momentum. Combining our new P_rot_ with precise BVIJHK photometry reported by Stauffer et al. (2007, J/ApJS/172/663) and Kamai et al. (2014, J/AJ/148/30), we investigate known anomalies in the photometric properties of K and M Pleiades members. We confirm the correlation detected by Kamai et al. between a star's P_rot_ and position relative to the main sequence in the cluster's color-magnitude diagram. We find that rapid rotators have redder (V-K) colors than slower rotators at the same V, indicating that rapid and slow rotators have different binary frequencies and/or photospheric properties. We find no difference in the photometric amplitudes of rapid and slow rotators, indicating that asymmetries in the longitudinal distribution of starspots do not scale grossly with rotation rate.
