- ID:
- ivo://CDS.VizieR/J/AJ/133/2072
- Title:
- Spitzer observations of NGC 2362
- Short Name:
- J/AJ/133/2072
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a mid-infrared imaging survey of the ~5Myr old cluster NGC 2362 carried out with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. The archival mid-infrared data were merged with extant Halpha emission data, optical and near-infrared photometry, and moderate-resolution optical spectroscopy to identify the remnant disk-bearing population of the cluster and to estimate the fraction of stars that still retain primordial circumstellar disks. The principal sample of 232 suspected cluster members with masses ranging from ~10 to 0.3M_{sun}_ (B2-M5 spectral types) was drawn from known Halpha emission stars, X-ray-detected stars from a single 100ks archival Chandra observation, and established lithium-rich stars. A second sample of 153 stars over a similar mass range whose membership status was based on optical photometry alone was also examined.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/698/1
- Title:
- Spitzer observations of NGC 2362
- Short Name:
- J/ApJ/698/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Expanding upon the Infrared Array Camera (IRAC) survey from Dahm & Hillenbrand (2007, Cat. J/AJ/133/2072), we describe Spitzer IRAC and Multiband Imaging Photometer for Spitzer observations of the populous, 5Myr old open cluster NGC 2362. We analyze the mid-IR colors of cluster members and compared their spectral energy distributions (SEDs) to star+circumstellar disk models to constrain the disk morphologies and evolutionary states. Combining our data with other Spitzer surveys, we investigate the evolution of debris disks around high/intermediate-mass stars and investigate timescales for giant planet formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/646/297
- Title:
- Spitzer observations of pre-main-sequence stars
- Short Name:
- J/ApJ/646/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Early observations of T Tauri stars suggested that stars with evidence of circumstellar accretion disks rotated slower than stars without such evidence, but more recent results are not as clear. Near-IR circumstellar disk indicators, although the most widely available, are subject to uncertainties that can result from inner disk holes and/or the system inclination. Mid-infrared observations are less sensitive to such effects, but until now, these observations have been difficult to obtain. The Spitzer Space Telescope now easily enables mid-infrared measurements of large samples of PMS stars covering a broad mass range in nearby star-forming regions. Megeath and collaborators surveyed the Orion Molecular Clouds (1Myr) with the IRAC instrument (3.6, 4.5, 5.8, 8um) as part of a joint IRAC and MIPS GTO program. We examine the relationship between rotation and Spitzer mid-IR fluxes for 900 stars in Orion for stars between 3 and 0.1M_{sun}_. We find in these Spitzer data the clearest indication to date that stars with longer periods are more likely than those with short periods to have IR excesses suggestive of disks.
- ID:
- ivo://CDS.VizieR/J/ApJ/662/1067
- Title:
- Spitzer observations of sigma Orionis
- Short Name:
- J/ApJ/662/1067
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new Spitzer Space Telescope observations, using the IRAC and MIPS instruments, of the young (~3Myr) sigma Orionis cluster. We identify 336 stars as members of the cluster, using optical and near-infrared color-magnitude diagrams. Using the spectral energy distribution slopes in the IRAC spectral range, we place objects into several classes: non-excess stars, stars with optically thick disks (such as classical T Tauri stars), class I (protostellar) candidates, and stars with "evolved disks"; the last exhibit smaller IRAC excesses than optically thick disk systems. In general, this classification agrees with the location expected in IRAC-MIPS color-color diagrams for these objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/679/720
- Title:
- Spitzer observations of the Hyades
- Short Name:
- J/ApJ/679/720
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Spitzer Space Telescope to search for infrared excess at 24, 70, and 160um due to debris disks around a sample of 45 FGK-type members of the Hyades. We supplement our observations with archival 24 and 70um Spitzer data of an additional 22 FGK-type and 11 A-type Hyades members in order to provide robust statistics on the incidence of debris disks at 625Myr of age, an era corresponding to the late heavy bombardment in the solar system. We find that none of the 67 FGK-type stars in our sample show evidence for a debris disk, while 2 out of the 11 A-type stars do. This difference in debris disk detection rate is likely to be due to a sensitivity bias in favor of early-type stars. The fractional disk luminosity, L_dust_/L_*_, of the disks around the two A-type stars is ~4x10^-5^, a level that is below the sensitivity of our observations toward the FGK-type stars. However, our sensitivity limits for FGK-type stars are able to exclude, at the 2{sigma} level, frequencies higher than 12% and 5% of disks with L_dust_/L_*_>1x10^-4^ and L_dust_/L_*_>5x10^-4^, respectively. We also use our sensitivity limits and debris disk models to constrain the maximum mass of dust, as a function of distance from the stars, that could remain undetected around our targets.
- ID:
- ivo://CDS.VizieR/J/ApJ/698/1989
- Title:
- Spitzer survey of NGC 2451
- Short Name:
- J/ApJ/698/1989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Spitzer IRAC and MIPS survey of NGC 2451A and B, two open clusters in the 50-80Myr age range. We complement these data with extensive ground-based photometry and spectroscopy to identify the cluster members in the Spitzer survey field. We find only two members with 8um excesses. The incidence of excesses at 24um is much higher, i.e., 11 of 31 solar-like stars and 1 of 7 early-type (A) stars. This work nearly completes the debris disk surveys with Spitzer of clusters in the 30-130Myr range. This range is of interest because it is when large planetesimal collisions may have still been relatively common (as indicated by the one that led to the formation of the Moon during this period of the evolution of the solar system). We review the full set of surveys and find that there are only three possible cases out of about 250 roughly solar-mass stars where very large excesses suggest that such collisions have occurred recently.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A13
- Title:
- Star cluster Gaia 1 stars equivalent widths
- Short Name:
- J/A+A/609/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star clusters, particularly those objects in the disk-bulge-halo interface are as yet poorly charted, despite the fact that they carry important information about the formation and the structure of the Milky Way. Here, we present a detailed chemical abundance study of the recently discovered object Gaia 1. Photometry has previously suggested it as an intermediate-age, moderately metal-rich system, although the exact values for its age and metallicity remained ambiguous in the literature. We measured detailed chemical abundances of 14 elements in four red giant members, from high-resolution (R=25000) spectra that firmly establish Gaia 1 as an object associated with the thick disk. The resulting mean Fe abundance is -0.62+/-0.03(stat.)+/-0.10(sys.) dex, which is more metal-poor than indicated by previous spectroscopy from the literature, but it is fully in line with values from isochrone fitting. We find that Gaia 1 is moderately enhanced in the {alpha}-elements, which allowed us to consolidate its membership with the thick disk via chemical tagging. The cluster's Fe-peak and neutron-capture elements are similar to those found across the metal-rich disks, where the latter indicate some level of s-process activity. No significant spread in iron nor in other heavy elements was detected, whereas we find evidence of light-element variations in Na, Mg, and Al. Nonetheless, the traditional Na-O and Mg-Al (anti-)correlations, typically seen in old globular clusters, are not seen in our data. This confirms that Gaia 1 is rather a massive and luminous open cluster than a low-mass globular cluster. Finally, orbital computations of the target stars bolster our chemical findings of Gaia 1's present-day membership with the thick disk, even though it remains unclear which mechanisms put it in that place.
- ID:
- ivo://CDS.VizieR/VII/5A
- Title:
- Star Clusters and Associations, Selected Data
- Short Name:
- VII/5A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog is a selection of data on all open clusters extracted from the second, considerably enlarged edition of the "Catalogue of Star Clusters and Associations" edited by Alter, Balazs, and Ruprecht (1970), which includes four parts: Part 1: 1039 open clusters, five moving clusters, and 11 stellar groups; Part 2: 70 OB associations; Part 3: 125 globular clusters; Part 4: 28 extragalactic objects. The catalog includes galactic and equatorial coordinates, name, classification, angular diameter, distance, magnitude and spectral types of the brightest stars, total magnitude, and color excess.
- ID:
- ivo://CDS.VizieR/J/AJ/157/12
- Title:
- Star clusters, associations, & candidates in the MW
- Short Name:
- J/AJ/157/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of Galactic star clusters, associations and candidates with 10978 entries. This multi-band catalog was constructed over 20 years, starting with visual inspections on the Digital Sky Survey and incremented with the 2MASS, WISE, VVV, Spitzer, and Herschel surveys. Large and small catalogs, as well as papers on individual objects have been systematically cross-identified. The catalog provides Galactic and equatorial coordinates, angular diameters, and chronologically ordered designations, making it simple to assign discoveries and verify how often the objects were cataloged by different authors, search methods, and/or surveys. Detection in a single band is the minimum constraint to validate an entry. About 3200 objects have measured parameters in the literature. A fundamental contribution of the present study is to present an additional ~7700 objects for the first analyses of nature, photometry, spectroscopy and structure. The present focus is not to compile or determine fundamental parameters, but to provide a catalog uniformly characterizing the entries. A major result is that now 4234 embedded clusters are cataloged, a factor of ~1.5 larger than open clusters. In addition to cross-identifications in different references and wavelength domains, we also communicate the discovery of 638 star clusters and similar objects. The present general catalog provides previously studied objects and thousands of additional entries in a homogeneous way, a timely contribution to Gaia-related works.
- ID:
- ivo://CDS.VizieR/VII/101A
- Title:
- Star Clusters/Associations. III. Open Clusters
- Short Name:
- VII/101A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue includes the Open Clusters of the supplement up to 1973 of the "Catalogue of Star Clusters and Associations" by Alter G., Ruprecht J., Vanysek V., Budapest 1970. The file "main.dat" contains the original data. For each cluster, the first line contains the running number (OCL) followed by various designations. The first five figures represent the galactic longitude (in 0.01degree), 'N' or 'S' for North or South galactic hemisphere, and galactic latitude (in 0.01degree). The second line contains the 1950 coordinates, the 50-yr precession, the galactic direction cosines and the position on the POSS charts. For each cluster a number of bibliographic records follow containing: YEAR: Year of the literature reference NAME: Author PUBLICATION: Reference AD: Angular diameter of the cluster in arc minutes DIST: Distance of the cluster (pc) LD: Linear diameter of the cluster (pc) N: Number of stars studied CI: Color index SP: Spectra P: Positions RV: Radial velocity (km/s) MT: Integrated magnitude NOTE: Notes The file "clusters" has been created from first and second lines; missing equatorial coordinates were derived from the galactic ones.
