Catálogo de publicaciones - revistas

<jats:title>ABSTRACT</jats:title> <jats:p>The <jats:italic>Chandra</jats:italic> Carina Complex Project (CCCP) provides a sensitive X-ray survey of a nearby starburst region over &gt;1 deg<jats:sup>2</jats:sup> in extent. Thousands of faint X-ray sources are found, many concentrated into rich young stellar clusters. However, significant contamination from unrelated Galactic and extragalactic sources is present in the X-ray catalog. We describe the use of a naive Bayes classifier to assign membership probabilities to individual sources, based on source location, X-ray properties, and visual/infrared properties. For the particular membership decision rule adopted, 75% of CCCP sources are classified as members, 11% are classified as contaminants, and 14% remain unclassified. The resulting sample of stars likely to be Carina members is used in several other studies, which appear in this special issue devoted to the CCCP.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>The key empirical property of the X-ray emission from O stars is a strong correlation between the bolometric and X-ray luminosities. In the framework of the <jats:italic>Chandra</jats:italic> Carina Complex Project, 129 O and B stars have been detected as X-ray sources; 78 of those, all with spectral type earlier than B3, have enough counts for at least a rough X-ray spectral characterization. This leads to an estimate of the <jats:italic>L</jats:italic> <jats:sub>X</jats:sub>–<jats:italic>L</jats:italic> <jats:sub>BOL</jats:sub> ratio for an exceptional number of 60 O stars belonging to the same region and triples the number of Carina massive stars studied spectroscopically in X-rays. The derived log(<jats:italic>L</jats:italic> <jats:sub>X</jats:sub>/<jats:italic>L</jats:italic> <jats:sub>BOL</jats:sub>) is −7.26 for single objects, with a dispersion of only 0.21 dex. Using the properties of hot massive stars listed in the literature, we compare the X-ray luminosities of different types of objects. In the case of O stars, the <jats:italic>L</jats:italic> <jats:sub>X</jats:sub>–<jats:italic>L</jats:italic> <jats:sub>BOL</jats:sub> ratios are similar for bright and faint objects, as well as for stars of different luminosity classes or spectral types. Binaries appear only slightly harder and slightly more luminous in X-rays than single objects; the differences are not formally significant (at the 1% level), except for the <jats:italic>L</jats:italic> <jats:sub>X</jats:sub>–<jats:italic>L</jats:italic> <jats:sub>BOL</jats:sub> ratio in the medium (1.0–2.5 keV) energy band. Weak-wind objects have similar X-ray luminosities but they display slightly softer spectra compared with “normal” O stars with the same bolometric luminosity. Discarding three overluminous objects, we find a very shallow trend of harder emission in brighter objects. The properties of the few B stars bright enough to yield some spectral information appear to be different overall (constant X-ray luminosities, harder spectra), hinting that another mechanism for producing X-rays, besides wind shocks, might be at work. However, it must be stressed that the earliest and X-ray brightest among these few detected objects are similar to the latest O stars, suggesting a possibly smooth transition between the two processes.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>The distribution of young stars found in the <jats:italic>Chandra</jats:italic> Carina Complex Project (CCCP) is examined for clustering structure. X-ray surveys are advantageous for identifying young stellar populations compared to optical and infrared surveys in suffering less contamination from nebular emission and Galactic field stars. The analysis is based on smoothed maps of a spatially complete subsample of ∼3000 brighter X-ray sources classified as Carina members and ∼10,000 stars from the full CCCP sample. The principal known clusters are recovered, and some additional smaller groups are identified. No rich embedded clusters are present, although a number of sparse groups are found. The CCCP reveals considerable complexity in clustering properties. The Trumpler 14 and 15 clusters have rich stellar populations in unimodal, centrally concentrated structures several parsecs across. Non-spherical internal structure is seen, and large-scale low surface density distributions surround these rich clusters. Trumpler 16, in contrast, is comprised of several smaller clusters within a circular boundary. Collinder 228 is a third type of cluster which extends over tens of parsecs with many sparse compact groups likely arising from triggered star formation processes. A widely dispersed, but highly populous, distribution of X-ray stars across the ∼50 pc CCCP mosaic supports a model of past generations of star formation in the region. Collinder 234, a group of massive stars without an associated cluster of pre-main-sequence stars, may be part of this dispersed population.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Using the highest-resolution X-ray observation of the Trumpler 15 star cluster taken by the <jats:italic>Chandra X-ray Observatory</jats:italic>, we estimate the total size of its stellar population by comparing the X-ray luminosity function (XLF) of the detected sources to a calibrator cluster and identify for the first time a significant fraction (∼14%) of its individual members. The highest-resolution near-IR observation of Trumpler 15 (taken by the HAWK-I instrument on the Very Large Telescope) was found to detect most of our X-ray selected sample of cluster members, with a <jats:italic>K</jats:italic>-excess disk frequency of 3.8% ± 0.7%. The near-IR data, XLF, and published spectral types of the brightest members support a cluster age estimate (5–10 Myr) that is older than those for the nearby Trumpler 14 and Trumpler 16 clusters, and suggest that high-mass members may have already exploded as supernovae. The morphology of the inner ∼0.7 pc core of the cluster is found to be spherical. However, the outer regions (beyond ∼2 pc) are elongated, forming an “envelope” of stars that, in projection, appears to connect Trumpler 15 to Trumpler 14; this morphology supports the view that these clusters are physically associated. Clear evidence of mass segregation is seen. This study appears in this special issue devoted to the <jats:italic>Chandra</jats:italic> Carina Complex Project, a 1.42 deg<jats:sup>2</jats:sup> <jats:italic>Chandra</jats:italic> X-ray survey of the Great Nebula in Carina.</jats:p>