Chandra X-Ray Observatory
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Last modified: 13 December 2012

URL: http://cxc.harvard.edu/csc/releases_dbaccess.html

Catalog Release Views and Current Database Views


Since Chandra is an on-going mission, new observations are continually becoming public. To distinguish between stable catalog versions and the source information extracted from recently released observations, there are two ways of viewing the CSC: catalog release views and current database views.

Catalog Release View

A catalog release view is a carefully reviewed, static version of the CSC. It is appropriate for the user who requires a detailed characterization of the statistical properties of the catalog, such as limiting sensitivity, completeness, false source rates, astrometric and photometric accuracy, and variability information. To be included in a catalog release view, a source must have a flux significance of 3.0σ or greater in at least one science energy band in a single observation. Once a name is assigned to a source in a catalog release view, the name remains frozen in time. In other words, the source will retain its originally assigned name through subsequent catalog releases, even if the most up-to-date information about that source renders its name unsuitable. It is possible that a source named in the current catalog release view will be removed from subsequent catalog release views; this could occur if the source does not meet the quality assurance criteria of the new catalog release, or if it is later discovered that the source is in fact an unresolved group of sources.

It is important to note that a catalog release view will never change, even if newly available data alters the knowledge of a source. The most current data is made available in the current database view, described below, and will ultimately be reflected in the next catalog release view. Access will be available to catalog releases prior to the most current, though access to file-based data products from previous releases is not guaranteed.

Current Database View

The current database view provides direct access to the active CSC database as it exists at the time of query submission. This view includes the most recently processed datasets which have not yet been included in a catalog release. A source must have a minimum flux significance of 3.0σ in at least one science energy band in a single observation to be included in the database view. The catalog database is updated continually as observations become publicly available.

Users who wish to search the latest data to identify sources with specific signatures for followup studies, for example, may prefer to do so in the current database view. However, since the current database view is dynamic, source characteristics and data products may be superseded at any time. Additionally, the statistical properties of data are not guaranteed.


Last modified: 13 December 2012
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