- 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.
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Search Results
- 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/ApJ/878/111
- Title:
- Members in Serpens Molecular Cloud with Gaia DR2
- Short Name:
- J/ApJ/878/111
- Date:
- 18 Jan 2022 15:09:42
- Publisher:
- CDS
- Description:
- The dense clusters within the Serpens Molecular Cloud are among the most active regions of nearby star formation. In this paper, we use Gaia DR2 parallaxes and proper motions to statistically measure ~1167 kinematic members of Serpens, few of which have been previously identified, to evaluate the star formation history of the complex. The optical members of Serpens are concentrated in three distinct groups located at 380-480pc; the densest clusters are still highly obscured by optically thick dust and have few optical members. The total population of young stars and protostars in Serpens is at least 2000 stars, including past surveys that were most sensitive to protostars and disks, and may be much higher. Distances to dark clouds measured from deficits in star counts are consistent with the distances to the optical star clusters. The Serpens Molecular Cloud is seen in the foreground of the Aquila Rift, dark clouds located at 600-700pc, and behind patchy extinction, here called the Serpens Cirrus, located at ~250pc. Based on the lack of a distributed population of older stars, the star formation rate throughout the Serpens Molecular Cloud increased by at least a factor of 20 within the past ~5Myr. The optically bright stars in Serpens Northeast are visible because their natal molecular cloud has been eroded, not because they were flung outwards from a central factory of star formation. The separation between subclusters of 20-100pc and the absence of an older population together lead to speculation that an external forcing was needed to trigger the active star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A166
- Title:
- Members of 5 cluster in Ori OB1a association
- Short Name:
- J/A+A/631/A166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Orion complex is arguably the most studied star-forming region in the Galaxy. While stars are still being born in the Orion nebula, the oldest part was believed to be no more than 13Myr old. In order to study the full hierarchy of star formation across the Orion complex, we perform a clustering analysis of the Ori OB1a region using new stellar surveys and derive robust ages for each identified stellar aggregate. We use Gaia DR2 parameters supplemented with radial velocities from the GALAH and APOGEE surveys to perform clustering of the Ori OB1a association. Five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). Most correspond to previously known structures (ASCC 16, 25 Orionis, ASCC 20, ASCC 21). We use Gaia DR2, Pan-STARRS1 and 2MASS photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. The ages of the clusters can thus be measured with 10% precision. While four of the clusters have ages between 11 and 13Myr, the ASCC 20 cluster stands out at an age of 21+/-3Myr. This is significantly greater than the age of any previously known component of the Orion complex. To some degree, all clusters overlap in at least one of the six phase-space dimensions. We argue that the formation history of the Orion complex, and its relation to the Gould belt, must be reconsidered. A significant challenge in reconstructing the history of the Ori OB1a association is to understand the impact of the newly discovered 21Myr old population on the younger parts of the complex, including their formation.
507. Members of IC 2391
- ID:
- ivo://CDS.VizieR/J/A+AS/126/357
- Title:
- Members of IC 2391
- Short Name:
- J/A+AS/126/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New 4-colour BV(RI)_KC_ CCD photometry to a limiting magnitude of V=~19 is presented for 1428 objects observed towards the direction of the young, open cluster IC 2391. We observed 36 (2'x3') fields within 17arcmin of the nominal cluster core. By fitting the theoretical isochrones of D'Antona & Mazzitelli (1994ApJS...90..467D) to a combination of colour-magnitude and colour-colour diagrams, we have identified 17 stars as probable cluster members with a further 85 stars as possible members. The brightness distribution of low-mass members is compared with the luminosity function observed for the Pleiades and we estimate that the contamination due to background giants should be small.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/87
- Title:
- Members of the young open cluster IC 2395
- Short Name:
- J/ApJ/832/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (~6-10Myr old), relatively nearby (800pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24{mu}m. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii from ~0.1 to ~10 au from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively, 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from ~1 to ~18Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24{mu}m excesses ([8]-[24]>=1.5) increases from (8.4+/-1.3)% at ~3Myr to (46+/-5)% at ~10Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.
- ID:
- ivo://CDS.VizieR/J/AJ/140/2109
- Title:
- Metallicites of open clusters NGC7160 and NGC2232
- Short Name:
- J/AJ/140/2109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a moderate-resolution spectroscopic analysis of the 10-25Myr clusters NGC 7160 and NGC 2232 using observations obtained with the WIYN 3.5m telescope. Both NGC 7160 and NGC 2232 are found to have super-solar metallicities, with a mean [Fe/H]=0.16+/-0.03(s.e.m.) for NGC 7160, and 0.22+/-0.09(s.e.m.) or 0.32+/-0.08 for NGC 2232, depending on the adopted temperature scale. NGC 7160 exhibits solar distributions of Na, Fe-peak, and alpha-elements. NGC 2232 is underabundant in light elements Al and Si, by ~0.25 and ~0.15dex, respectively; [Ni/Fe] is roughly solar. The abundance of lithium in NGC 2232 stars is in agreement with undepleted values reported for other cluster main-sequence stars. Our abundances are similar to other metal-rich open clusters and Galactic thin and thick disk stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/3042
- Title:
- Metallicities in the Geneva photometric system
- Short Name:
- J/MNRAS/469/3042
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the most homogeneous Geneva seven-colour photometric system to derive new metallicity calibrations for early A- to K-type stars that cover both, dwarf stars and giants. The calibrations are based on several spectroscopic data sets that were merged to a common scale, and we applied them to open cluster data to obtain an additional proof of the metallicity scale and accuracy. In total, metallicities of 54 open clusters are presented. The accuracy of the calibrations for single stars is in general below 0.1dex, but for the open cluster sample with mean values based on several stars we find a much better precision, a scatter as low as about 0.03dex. Furthermore, we combine the new results with another comprehensive photometric data set to present a catalogue of mean metallicities for more than 3000 F- and G-type dwarf stars with sigma about 0.06dex. The list was extended by more than 1200 hotter stars up to about 8500K (or spectral type A3) by taking advantage of their almost reddening free characteristic in the new Geneva metallicity calibrations. These two large samples are well suited as primary or secondary calibrators of other data, and we already identified about 20 spectroscopic data sets that show offsets up to about 0.4dex.
