A. A. Suchkov

Automated Classification of ROSAT Sources Using Heterogeneous Multiwavelength Source Catalogs

We describe an online system for automated classification of X-ray sources, ClassX, and we present preliminary results of classification of the three major catalogs of ROSAT sources, ROSAT All-Sky Survey (RASS) Bright Source Catalog, RASS Faint Source Catalog, and WGACAT, into six class categories: stars, white dwarfs, X-ray binaries, galaxies, active galactic nuclei, and clusters of galaxies. ClassX is based on a machine-learning technology. It represents a system of classifiers, each classifier consisting of a considerable number of oblique decision trees. These trees are built as the classifier is trained to recognize various classes of objects using a training sample of sources of known object types. Each source is characterized by a preselected set of parameters, or attributes; the same set is then used as the classifier conducts classification of sources of unknown identity. The ClassX pipeline features an automatic search for X-ray source counterparts among heterogeneous data sets in online data archives using Virtual Observatory protocols; it retrieves from those archives all the attributes required by the selected classifier and inputs them to the classifier. The user input to ClassX is typically a file with target coordinates, optionally complemented with target IDs. The output contains the class name, attributes, and class probabilities for all classified targets. We discuss ways to characterize and assess the classifier quality and performance, and we present the respective validation procedures. On the basis of both internal validation and external verification, we conclude that the ClassX classifiers yield reasonable and reliable classifications for ROSAT sources and have the potential to broaden class representation significantly for rare object types.

Evidence for a Very Young Age of F Stars with Extrasolar Planets

We assess the age of nine planet-bearing (PB) F stars by comparing their metallicity, Hp variability, brightness anomaly, and location in the color-magnitude diagram with the same parameters for the Hyades and field F stars. Combined evidence from these parameters suggests that the age of our PB F stars is not very much different from the age of the Hyades, ~700 Myr, and is much younger than the ages of cooler, solar-type PB stars found in a number of recent studies.

Candidate Pre–Main-Sequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and [CLC][ITAL]uvby[/ITAL][/CLC] Data

We propose a method that uses near-infrared plus uvby photometry to identify potentially extensive circumstellar dusty environments around F and A stars. The method has been applied to a sample of ~900 metal-rich reddened F stars with 2 Micron All Sky Survey and uvby data, suggesting the presence of circumstellar dust emitting in the near-infrared for ~70 stars. The log Te-MV diagram suggests that most, if not all, are likely pre-main-sequence (PMS) stars. They seem to be a continuation of the class of Herbig Ae/Be PMS stars in the spectral type F. Their number drops sharply downward of log Te ~ 3.84 (spectral types later than ~F5), which may provide new clues to the PMS evolution of 1-2 M☉ stars. We present a list of 21 of the most conspicuous candidate stars with circumstellar dust. About half of them are associated with the extended star-forming region around ρ Ophiuchi. The brightest of these 21 stars, with V 7.5, turn out to be IRAS sources, suggesting the presence of heated dust emitting in the far-infrared. Also in this list, HD 81270 is reported as a very unusual star moving away from the Galactic plane at a projected speed of 70 km s-1.

Candidate Pre-Mainsequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and uvby Data

We propose a method that uses near-infrared plus uvby photometry to identify potentially extensive circumstellar dusty environments around F and A stars. The method has been applied to a sample of ~900 metal-rich reddened F stars with 2 Micron All Sky Survey and uvby data, suggesting the presence of circumstellar dust emitting in the near-infrared for ~70 stars. The log Te-MV diagram suggests that most, if not all, are likely pre-main-sequence (PMS) stars. They seem to be a continuation of the class of Herbig Ae/Be PMS stars in the spectral type F. Their number drops sharply downward of log Te ~ 3.84 (spectral types later than ~F5), which may provide new clues to the PMS evolution of 1-2 M☉ stars. We present a list of 21 of the most conspicuous candidate stars with circumstellar dust. About half of them are associated with the extended star-forming region around ρ Ophiuchi. The brightest of these 21 stars, with V 7.5, turn out to be IRAS sources, suggesting the presence of heated dust emitting in the far-infrared. Also in this list, HD 81270 is reported as a very unusual star moving away from the Galactic plane at a projected speed of 70 km s-1.

Candidate Pre-Main-Sequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and uvby Data

We propose a method that uses near-infrared plus uvby photometry to identify potentially extensive circumstellar dusty environments around F and A stars. The method has been applied to a sample of ~900 metal-rich reddened F stars with 2 Micron All Sky Survey and uvby data, suggesting the presence of circumstellar dust emitting in the near-infrared for ~70 stars. The log Te-MV diagram suggests that most, if not all, are likely pre-main-sequence (PMS) stars. They seem to be a continuation of the class of Herbig Ae/Be PMS stars in the spectral type F. Their number drops sharply downward of log Te ~ 3.84 (spectral types later than ~F5), which may provide new clues to the PMS evolution of 1-2 M☉ stars. We present a list of 21 of the most conspicuous candidate stars with circumstellar dust. About half of them are associated with the extended star-forming region around ρ Ophiuchi. The brightest of these 21 stars, with V 7.5, turn out to be IRAS sources, suggesting the presence of heated dust emitting in the far-infrared. Also in this list, HD 81270 is reported as a very unusual star moving away from the Galactic plane at a projected speed of 70 km s-1.

Classifying the high energy universe with ClassX

Building an automated classifier for high-energy sources provides an opportunity to prototype approaches to building the Virtual Observatory with a substantial immediate scientific return. The ClassX collaboration is combining existing data resources with trainable classifiers to build a tool that classifies lists of objects presented to it. In our first year the collaboration has concentrated on developing pipeline software that finds and combines information of interest and in exploring the issues that will be needed for successful classification. ClassX must deal with many key VO issues: automating access to remote data resources, combining heterogeneous data and dealing with large data volumes. While the VO must attempt to deal with these problems in a generic way, the clear science goals of ClassX allow us to act as a pathfinder exploring particular approaches to addressing these issues.