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A1: Help

A1 - HEAO 1 A-1 X-Ray Source Catalog


Overview

The HEAO 1 A-1 X-Ray Source Catalog contains information about X-ray sources detected with the NRL Large Area Sky Survey Experiment (also referred to as the A-1 Experiment) flown aboard the HEAO-1 satellite. The catalog represents results from the first six months of data from HEAO-1, during which time a scan of the entire sky was completed. Positions and intensities for 842 sources are listed, with a limiting flux of 250 nanoJanskies (nJy) at 5 keV, or about 0.25 Uhuru flux units (UFU). The catalog is more than 90% complete at a flux level equivalent to 1.5 microJanskies (uJy) at 5 keV, for a Crab-like spectrum.

The A-1 catalog has been cross-referenced with published literature. Identifications based on coincidence in position have been proposed for some of the sources for which previous work has established no firm identification. Half of the sources remained unidentified at the time of catalog publication (1984). The A3 database contains a list of 654 optical objects identified with A-1 error boxes.


Catalog Bibcode

1984ApJS...56..507W

Provenance

Minor structural changes were made to this database table and the documentation was revised by the HEASARC in July 2004. The basic content of the database table was unchanged, however.

Description

The primary objective of the HEAO 1 A-1 Experiment was to generate an all-sky survey of the brightest X-ray sources in the energy range from 0.25 to 25 keV. The A-1 instrumentation consisted of an array of large-aperture proportional counter modules with collimators of varying fields of view. The present catalog is derived from the first six months of operation, during which full sky coverage was achieved by continuously scanning great circles perpendicular to the Earth-Sun line.

Reference

The observations, instrumentation, and data analysis techniques used to produce the A-1 catalog as well as the catalog itself, are described in detail in "The HEAO A-1 X-Ray Source Catalog", by K.S.Wood et al. 1984, ApJS, 56, 507-649.

Parameters

Alternate_X_Ray_1
Alternate X-ray designation for the source.

Alternate_X_Ray_2
Alternate X-ray designation for the source.

Alternate_X_Ray_3
Alternate X-ray designation for the source.

Alternate_X_Ray_4
Alternate X-ray designation for the source.

Alternate_X_Ray_5
Alternate X-ray designation for the source.

Alternate_X_Ray_6
Alternate X-ray designation for the source.

Alternate_X_Ray_7
Alternate X-ray designation for the source.

Area
The solid angle enclosed by the error box, in square degrees.

Beta
Ecliptic latitude of the source (center of the error box).

BII
Galactic latitude of the source (center of the error box).

Count_Rate
The apparent intensity of the source in counts cm^(-2) s^(-1) in the 0.5 to 25 keV energy band. An intensity of 0.001 cts cm^(-2) s^(-1) (the limiting flux of the catalog) corresponds to 3.3 x 10^(-12) erg cm^(-2) s^(-1) in the 2 - 6 keV band, or 4.78 x 10^(-12) erg cm^(-2) s^(-1) in the 2 - 10 keV band, both for a Crab-like spectrum. This means that 0.001 cts cm^(-2) s^(-1) in HEAO A-1 is equivalent to 0.20 UFU or to 0.22 uJy at 5.2 keV, again for a Crab-like spectrum.

Count_Rate_Error
The error in the count rate, as determined by the methods discussed in Section 3 of the published paper.

Dec
The source declination (center of error box) in the specified equinox. This was given in B1950 coordinates to a precision of 1 arcsecond in the published version of the catalog.

Dec1
Declination (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

Dec2
Declination (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

Dec3
Declination (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

Dec4
Declination (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

Lambda
Ecliptic longitude of the source (center of the error box).

LII
Galactic longitude of the source (center of the error box).

Name
The catalog name of the source; the catalog designation is composed of the prefix `1H`, followed by the right ascension in hours and minutes and the declination in degrees and tenths of a degree (1950.0).

Non_X_Ray_Id_1
A possible non-X-ray identification for the source.

Non_X_Ray_Id_2
A possible non-X-ray identification for the source.

Non_X_Ray_Id_3
A possible non-X-ray identification for the source.

Non_X_Ray_Id_4
A possible non-X-ray identification for the source.

RA
The source right ascension (center of error box) in the specified equinox. This was given in B1950 coordinates to a precision of 1 second of time in the published version of the catalog.

RA1
Right ascension (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

RA2
Right ascension (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

RA3
Right ascension (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.

RA4
Right ascension (in degrees, and in J2000.0 coordinates for the Browse Web Interface, but B1950.0 coordinates for the EXOSAT Browse CLI table) of one corner of the 95% confidence error box surrounding the source.


Contact Person

Questions regarding the A1 database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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