- ID:
- ivo://CDS.VizieR/J/A+A/324/91
- Title:
- Melotte 71 red giants radial velocities
- Short Name:
- J/A+A/324/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CORAVEL radial-velocity observations and UBV photometry of 24 red giants in the field of the intermediate-age open cluster Mel 71 are analysed for membership and duplicity. The membership of 16 stars is confirmed, one star is a possible member, and 8 spectroscopic binaries have been discovered, all amongst the cluster stars. Four of their orbits have been determined, with periods ranging from 74 to 1627 days. The mean cluster velocity is +50.14+/-0.14 (s.e.)km/s, and the binary frequency is unusually high (8/16=50%). The best isochrone fit to the observed colour-magnitude digram is obtained for logt=9.00 and Z=0.008. However, some discrepancies appear between the observed and predicted locations of the red giant clump.
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- ID:
- ivo://CDS.VizieR/J/A+A/643/A71
- Title:
- Members for 20 open clusters
- Short Name:
- J/A+A/643/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity. We perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open clusters. Based on the parameters derived from the GES spectroscopic observations, we obtained lists of candidate members for each of the clusters in the sample by deriving RV distributions and studying the position of the kinematic selections in the EW(Li) versus Teff plane to obtain lithium members. We used gravity indicators to discard field contaminants and studied [Fe/H] metallicity to further confirm the membership of the candidates. We also made use of studies using recent data from the Gaia DR1 and DR2 releases to assess our member selections. We identified likely member candidates for the sample of 20 clusters observed in GES (iDR4) with UVES and GIRAFFE, and conducted a comparative study that allowed us to characterize the properties of these members, as well as identify field contaminant stars, both lithium-rich giants and non-giant outliers. This work is the first step towards the calibration of the lithium-age relation and its dependence on other GES parameters. During this project we aim to use this relation to infer the ages of GES field stars, and identify their potential membership to young associations and stellar kinematic groups of different ages.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A85
- Title:
- Membership and lithium of young clusters
- Short Name:
- J/A+A/659/A85
- Date:
- 10 Mar 2022 07:23:16
- Publisher:
- CDS
- Description:
- It is now well known that pre-main sequence models with inflated radii should be taken into account to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern observed in young open star clusters. We test a new set of pre-main sequence models including radius inflation due to the presence of starspots or to magnetic inhibition of convection, using five clusters observed by the Gaia-ESO Survey, spanning the age range ~10-100Myr where such effects could be important. The Gaia-ESO Survey radial velocities are combined with astrometry from Gaia EDR3 to obtain clean lists of high-probability members for the five clusters. A Bayesian maximum likelihood method is adopted to fit the observed cluster sequences to theoretical predictions to derive the best model parameters and the cluster reddening and age. Models are calculated with different values of the mixing length parameter ({alpha}_ML_=2.0, 1.5 and 1.0), for the cases with no spots or with effective spot coverage {beta}_spot_=0.2 and 0.4. The models are also compared with the observed lithium depletion patterns. To reproduce the colour-magnitude diagram and the observed lithium depletion pattern in Gamma Vel A and B and in 25 Ori one needs to assume both a reduced convection efficiency, with {alpha}_ML_=1.0, and an effective surface spot coverage of about 20%. We obtained ages of 18^+1.5^_-4.0_ Myr and 21^+3.5^_-3.0_ Myr for Gamma Vel A and B, respectively, and 19^+1.5^_-7.0_ Myr for 25 Ori. However, a single isochrone is not sufficient to account for the lithium dispersion, and an increasing level of spot coverage as mass decreases seems to be required. On the other hand, the older clusters (NGC 2451B at 30^+3.0^_-5.0_Myr, NGC 2547 at 35^+4.0^_-4.0_Myr, and NGC 2516 at 138^+48^_-42_Myr) are consistent with standard models, with {alpha}_ML_=2.0 and no spots, except at low masses: a 20% spot coverage appears to better reproduce the sequence of M-type stars and might explain the observed spread in lithium abundances. The quality of Gaia-ESO data combined with Gaia allows us to gain important insights on pre-main sequence evolution. Models including starspots can provide a consistent explanation of the cluster sequences and lithium abundances observed in young clusters, although a range of starspot coverage is required to fully reproduce the data.
- ID:
- ivo://CDS.VizieR/J/A+A/461/509
- Title:
- Membership and spectroscopy of IC 2391
- Short Name:
- J/A+A/461/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young open clusters provide important clues to the interface between the main sequence and pre-main-sequence phases of stellar evolution. The young and nearby open cluster IC 2391 is well-suited to studies of these two evolutionary phases. We establish a bona fide set of cluster members and then analyze this set in terms of binary frequency, projected rotational velocities, [Fe/H], and lithium abundance. In the wake of the Hipparcos distance controversy for the Pleiades, we compare the main-sequence fitting distance modulus to the Hipparcos mean parallax for IC 2391.
- ID:
- ivo://CDS.VizieR/J/AJ/134/2340
- Title:
- Membership of Praesepe and Coma Berenices clusters
- Short Name:
- J/AJ/134/2340
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a stellar membership survey of the nearby open clusters Praesepe and Coma Berenices. We have combined archival survey data from the SDSS, 2MASS, USNOB1.0, and UCAC-2.0 surveys to compile proper motions and photometry for ~5 million sources over 300{deg}^2^. Of these sources, 1010 stars in Praesepe and 98 stars in Coma Ber are identified as candidate members with probability >80%; 442 and 61 are identified as high-probability candidates for the first time. We estimate that this survey is >90% complete across a wide range of spectral types (F0-M5 in Praesepe, F5-M6 in Coma Ber). We have also investigated the stellar mass dependence of each cluster's mass and radius in order to quantify the role of mass segregation and tidal stripping in shaping the present-day mass function and spatial distribution of stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/3108
- Title:
- Membership of Sco OB2 moving group
- Short Name:
- J/MNRAS/416/3108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new high-mass membership of the nearby Sco OB2 association based on Hipparcos positions, proper motions and parallaxes, and radial velocities taken from the 2nd Catalogue of Radial Velocities with Astrometric Data (CRVAD-2). The Bayesian membership selection method developed makes no distinction between subgroups of Sco OB2 and utilizes linear models in calculation of membership probabilities. We select 436 members, 88 of which are new members not included in previous membership selections. We include the classical non-members alpha-Cru and beta-Cru as new members as well as the pre-main-sequence stars HIP 79080 and 79081. We also show that the association is well mixed over distances of 8{deg} on the sky, and hence no determination can be made as to the formation process of the entire association.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/353
- Title:
- Membership of the Orion nebula population
- Short Name:
- J/ApJS/160/353
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Orion Ultradeep project (COUP) observation described in a companion paper by Getman et al. (2005, Cat. J/ApJS/160/319) provides an exceptionally deep X-ray survey of the Orion Nebula Cluster and associated embedded young stellar objects. Membership of the region is important for studies of the stellar IMF, cluster dynamics, and star formation. The COUP study detected 1616 X-ray sources. In this study we confirm cloud membership for 1315 stars, identify 16 probable foreground field stars having optical counterparts with discrepant proper motions, and classify the remaining 285 X-ray sources, of which 51 are lightly and 234 heavily obscured.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A15
- Title:
- Membership probabilities of Pleiades objects
- Short Name:
- J/A+A/617/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photometric and astrometric measurements of the Pleiades DANCe DR2 survey provide an excellent test case for the benchmarking of statistical tools aiming at the disentanglement and characterisation of nearby young open cluster (NYOC) stellar populations. We aim to develop,test, and characterise of a new statistical tool (intelligent system) for the sifting and analysis of NYOC populations. Using a Bayesian formalism, with this statistical tool we were able to obtain the posterior distributions of parameters governing the cluster model. It also used hierarchical bayesian models to establish weakly informative priors, and incorporates the treatment of missing values and non-homogeneous (heteroscedastic) observational uncertainties. From simulations, we estimated that this statistical tool renders kinematic (proper motion) and photometric (luminosity) distributions of the cluster population with a contamination rate of 5.8+/-0.2%. The luminosity distributions and present day mass function agree with the ones found in a recent study, on the completeness interval of the survey. At the probability threshold of maximum accuracy, the classifier recovers ~90% of the recently published candidate members and finds 10% of new ones. A new statistical tool for the analysis of NYOC is introduced, tested, and characterised. Its comprehensive modelling of the data properties allows it to get rid of the biases present in previous works. In particular, those resulting from the use of only completely observed (non-missing) data and the assumption of homoskedastic uncertainties. Also, its Bayesian framework allows it to properly propagate observational uncertainties into membership probabilities and cluster velocity and luminosity distributions. Our results are in a general agreement with those from the literature, although we provide the most up-to-date and extended list of candidate members of the Pleiades cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/345/471
- Title:
- Memberships of open clusters
- Short Name:
- J/A+A/345/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New memberships, mean parallaxes and proper motions of all 9 open clusters closer than 300pc (except the Hyades) and 9 rich clusters between 300 and 500pc have been computed using Hipparcos (Cat. <I/239>) data. Precisions, ranging from 0.2 to 0.5mas for parallaxes and 0.1 to 0.5mas/yr for proper motions, are of great interest for calibrating photometric parallaxes as well as for kinematical studies. Careful investigations of possible biases have been performed and no evidence of significant systematic errors on the mean cluster parallaxes has been found. The distances and proper motions of 32 more distant clusters, which may be used statistically, are also indicated.
- ID:
- ivo://CDS.VizieR/J/AJ/109/1903
- Title:
- Membership to cluster IC 4756
- Short Name:
- J/AJ/109/1903
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our method for determining statistically the members of an open cluster by means of the proper motions (Missana et al., (1990AJ....100.1850M) is amended and its validity is verified by applying it to the cluster IC 4756 with the data given by Herzog et al. (1975A&AS...19..211H), adding nothing to their results. In the computation of the dispersion ellipses of the samples and of the {chi}^2^ for deriving the significance levels, the weights of the proper motions have been taken into account. The results obtained by the criterion of the {chi}^2^ and those obtained by Herzog et al. by the criterion of the maximum likelihood of Sanders (1971A&A....14..226S) are concordant.