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HRICFA - Einstein Catalog HRI CFA Sources



This database table consists of a preliminary source list for the Einstein Observatory's High Resolution Imager (HRI). The source list, obtained from EINLINE, the Einstein On-line Service at the Smithsonian Astrophysical Observatory (SAO), contains basic information about the sources detected with the HRI.


The HRI was one of the four focal-plane instruments in the Einstein Observatory. The HRI, supplied by SAO, had the highest spatial resolution on Einstein but had relatively low quantum efficiency.

The HRI source list contained in the Einline database is version #1, released on 17 November 1989. Results taken from this list should be used with caution, as the list is in a more primitive state than the IPC source list (contained in the IPC database). The data were taken essentially unchanged from the results of the HRI Rev 1 processing at SAO. The HRI source list has been screened manually for obvious errors, but not as thoroughly as the IPC list. In particular, a number of extended sources were not picked out by the standard source detection algorithm and so are not included in the HRI list. As of spring 1991 (when this database was created), the final version of the HRI Source Catalog, the analog of the IPC Source Catalog, had yet to be released.


The galactic latitude of the source, calculated from the given RA and Dec.

Each source has been assigned a `catalog designation`. The catalog designations have the format `HRIhhmmss+ddmm`, with `hhmmss` representing hours, minutes and seconds of RA and `+ddmm` representing degrees and minutes of declination.

The corrected count rate. For the HRI source list, the count rate is obtained by summing all counts within a circle of radius 18 arc seconds centered on the source position, and then applying the HRI correction factors for exposure time, vignetting, deadtime, mirror scattering, and quantum efficiency.

The count rate error is estimated with this equation:

    Error = ((BCTS^1/2)/BCTS) * Count Rate
where `BCTS` is the sum of all counts inside the detection box of side = 12 arc seconds.

The declination of the source.

Field number for the source.

The galactic longitude of the source, calculated from the given RA and Dec.

The common name of the source, assigned by cross-correlating the HRICFA database with other online catalogs.

90-percent uncertainty in the coordinates in arc seconds. It includes a statistical contribution added in quadrature to a systematic term.

The right ascension of the source.

HRI source flag.

The source flag codes are as follows:

   * X = This source shows obvious extent.
   * U = The count rate for this source has been underestimated, because it is
         either extended, confused, or at the edge of the field of view.
   * C = The source lies in a confused region; its position and count rate may be
         seriously in error.

This is a sequence number for the observation associated with each source. The sequence number is a unique numeric identifier for an observation, allocated sequentially at time of proposal submission.

The signal-to-noise ratio of the detection. For the HRI source list, this is a conservative estimate, since for small numbers of counts the Poisson errors are significantly asymmetric.

Contact Person

Questions regarding the HRICFA database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 9-Nov-2004