A1 Catalog
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.
A1POINT Catalog
HEAO 1 (High Energy Astronomical Observatory) is a spinning
survey mission X-ray satellite. It launched 12 August 1977
and was in operation until 9 January 1979. HEAO-1 rotated
once per 30 minutes about the Earth-Sun line. In this manner,
the instruments scanned a great circle in the sky that lay 90
degrees from the sun.
A given source near the ecliptic was viewed for a few days while
sources near the ecliptic pole were scanned nearly continuously
during the entire mission. The satellite has limited pointing
capability that was used to produce this data, giving continuous
coverage of selected sources. The pointings began about 100 days
into the mission.
The A1 instrument, also known as the NRL Large Area Sky Survey
Experiment (LASS) covered the energy range 0.25 to 25.0 keV. The
experiment consisted of seven detectors, six mounted on the -Y
side of the spacecraft, the seventh on the +Y side. Two detectors,
with a FWHM of 1 deg x 0.5 deg and open area of 1350 cm2 were
tilted a third of a degree either towards or away from the Z
(Sun-pointed) four other -Y side detectors has a FWHM of 1 deg
x 4 deg and an open area of 1650 cm2. The single +Y detector has
a FWHM of 2 deg x 8 deg and an open area of 1900 cm2. The experiment
had sufficient sensitivity to detect sources as faint as as 0.25
uJy at 5 keV for sources with a Crab-like spectrum. Data was
collected in either a 5 or a 320 millisecond timing resolution
mode: Full sky coverage for both time resolutions was achieved
before the mission's end. Wood et al. (1984) discuss the experiment
and a catalog of sources in further detail.
A2LCPOINT Catalog
The A2 experiment was flown on the HEAO-1 satellite, from August, 1977
until January 1979.
The experiment consisted of six multi-layer, multi-anode collimated gas
proportional counters. These were two LEDs (Low Energy Detectors), a
MED (Medium Energy Detector), and three HEDs (High Energy Detectors).
The first 6-months of mission were dedicated to an all-sky scan after
which a pointing phase started.
This database table accesses the lightcurves available at HEASARC obtained
from the A2 MED (small and large field of view) and HEDs (3 units, each
with small and large field of view) detectors during the pointed phase.
A2LCSCAN Catalog
The A2 experiment was flown on the HEAO-1 satellite, from August, 1977
until January 1979.
The experiment consisted of six multi-layer, multi-anode collimated gas
proportional counters. These were two LEDs (Low Energy Detectors), a
MED (Medium Energy Detector), and three HEDs (High Energy Detectors).
The first 6-months of mission were dedicated to an all-sky scan after
which a pointing phase started.
This database table accesses the lightcurves available at HEASARC obtained
from the A2 MED (small and large field of view) and HEDs (3 units, each
with small and large field of view) detectors during the scanning phase.
A2LED Catalog
The HEAO 1 A-2 LED Catalog of High-Energy X-ray Sources is the result of a
study of the diffuse X-ray sky over the bands of X-ray energies 0.18-0.44 keV
and 0.44-2.8 keV from August 1977 until January 1979 using data obtained with
the A-2 Low Energy Detector on the HEAO 1 satellite. The HEAO A-2 Experiment
was primarily designed for studying the diffuse X-ray background; however, it
was also capable of studying point sources to good sensitivity. The detectors
surveyed over 95 percent of the sky in the spectral bands listed above to
typical limiting sensitivities of 1x10**-11 and 3x10**-11 respectively. Using
a significance criterion of 6 sigma for existence, 114 sources are cataloged.
The catalog contains a list of all counterpart identifications and a
cross-reference to all HEAO 1 A-2 LED team publications on the catalog sources
complete through the end of 1981.
The identified sources fall into several categories, primarily dependent on
observing energy interval. In the 1 KeV band the sources include: 20 galactic
stellar sources, 19 extragalactic sources, 13 SNR's, 11 galactic bulge sources,
2 globular cluster sources, and 2 previously reported sources without optical
counterparts. In the .25 KeV band the sources include: 24 galactic stellar
objects, 12 extragalactic sources, 5 SNR's, 1 bulge source, and 1 globular
cluster source.
A2PIC Catalog
The HEAO 1 A-2 experiment's operations began on day 224 of 1977 (12 August
1977) and ended on day 739 of 1977 (9 January 1979). The A-2 experiment
performed two independent, low-background, high-sensitivity surveys of the
entire sky 6 months apart, the first scan during days 248 to 437 of 1977
(5 September 1977 - 13 March 1978) and the second scan during days 73 to 254
of 1978 (14 March 1978 - 11 September 1978). The authors analyzed the A-2
data in order to obtain a complete flux-limited sample of extragalactic
X-ray sources. The region between galactic latitudes of -20 and +20 degrees
was excluded to minimize contamination from galactic sources. A circle of
6 degrees radius around the Large Magellanic Cloud sources was also
excluded to prevent confusion problems. Therefore, there remained 65.5%
of the sky (8.23 steradians) covered by this survey. The lowest statistical
significance for the existence of the sources included in this catalog
is 5 sigma, as required by the maximum likelihood methods used by the
authors to determine the log N - log S parameters. Taking into account this
statistical significance requirement, the authors estimated the completeness
level of the first and second scans to be 1.25 and 1.8 R15 ct/s, respectively.
1 R15 ct/s is approximately 2.17 x 10-11 erg/cm2/s in the 2-10 keV energy
band for a power-law spectrum with a photon index of 1.65. This catalog
contains data for 68 non-galactic sources (61 extragalactic and 7 unidentified
sources) which were listed in Table 1 of the published catalog.
The identified sources fall into several categories, including narrow
emission line galaxies, broad emission line galaxies, BL Lacertae objects,
and clusters of galaxies.
A2POINT Catalog
The HEAO 1 A-2 Pointing Catalog of High-Energy X-ray Sources is the result of
a study of selected targets using the three detectors of the A-2 Experiment.
The detectors consisted of the HED (high energy detector) in the range 3-6
KeV, the MED (medium energy detector) in the range 1.5-15 KeV, and the LED
(low energy detector) in the range 0.15-3 KeV. The HEAO A-2 Experiment was
primarily designed for studying the diffuse X-ray background; however, it was
also capable of studying point sources to good sensitivity. Thus, after
several months of continuous scanning to survey 95% of the diffuse X-ray sky,
the A-2 detectors began individual pointings at selected targets. The point
maneuvers began on day 319, 15 November 1977 and ended on day 739, 9 January
1979.
A2RTRAW Catalog
The A2 experiment was flown on the HEAO-1 satellite, between August, 1977
until January 1979. The experiment consisted of six multi-layer multi-anode
collimated gas proportional counters. These were two LEDs (Low Energy
Detectors), a MED (Medium Energy Detector), and three HEDs (High Energy
Detectors). The first 6-months of mission were dedicated to an all-sky scan
after which a pointing phase started. This database accesses the raw rate data
obtained from the A2 MED (small and large field of view, FOV) and HEDs (1,2
and 3 small and large filed of view) detectors during the scanning and pointed
phase.
Note: This database does not contain coordinates. Since the satellite was
mostly scanning, the XRATE database, from which the FITS files are generated,
was organized in time.
A2SPECBACK Catalog
The A2 experiment was flown on the HEAO-1 satellite, between August, 1977
until January 1979.
The experiment consisted of six multi-layer multi-anode collimated gas
proportional counters. These were two LEDs (Low Energy Detectors), a MED
(Medium Energy Detector), and three HEDs (High Energy Detectors). The first
6-months of mission were dedicated to an all-sky scan after which a pointing
phase started.
This database table accesses all the background files available at HEASARC
obtained from the A2 MED (small and large field of view) and HEDs (1 and 3
small and large filed of view) detectors during the pointed phase.
A2SPECTRA Catalog
The A2 experiment was flown on the HEAO-1 satellite, between August, 1977
until January 1979. The experiment consisted of six multi-layer multi-anode
collimated gas proportional counters. These were two LEDs (Low Energy
Detectors), a MED (Medium Energy Detector), and three HEDs (High Energy
Detectors). The first 6-months of mission were dedicated to an all-sky scan
after which a pointing phase started. This database accesses the spectra (and
associated files) obtained from the A2 MED (small and large field of view)
and HEDs (1 and 3 small and large filed of view) detectors during the pointed
phase. The spectra were generated for all HEAO-1 A2 pointed observations
except for those in more unusual HEAO-1 modes (RAM-11 and "radical RAMs").
Thus the set of spectra created are only a subset (though a fairly complete
one) of the entire catalog of HEAO-1 A2 pointed observations.
A3 Catalog
This database table contains information from the HEAO 1 A3 MC LASS Catalog
of X-ray Sources. The MC experiment contained two four-grid modulation
collimators with an egg-crate collimator with an overall FOV of 4 x 4 degrees
(FWHM). The objects in the catalog are possible HEAO 1 A1 sources. The HEAO 1
experiment began on day 224, 19 August 1977 and ended on day 739, 9 January
1979.
A4 Catalog
The HEAO 1 A-4 Catalog of High-Energy X-ray Sources represents results from an
all-sky survey carried out at high X-ray energies (13-180 keV) from August 1977
until January 1979 using data obtained with the UCSD/MIT Hard X-Ray and
Low-Energy Gamma-Ray Instrument on the HEAO 1 satellite. Quantitative results
from a model-dependent fitting procedure are given in the form of fitted count
rates in four broad energy bands for about 70 sources. The survey is complete,
except in regions of source confusion, down to an intensity level of about 1/75
of the Crab Nebula in the 13-80 keV energy band. Forty-four sources were
detected in the 40-80 keV energy band, and 14 in the 80-180 keV band. Most of
the sources are galactic; seven are extragalactic.
A4SPECTRA Catalog
The UCSD/MIT Hard X-Ray and Low-Energy Gamma-Ray Instrument, A4, was flown on
the HEAO 1 satellite, between August 1977 until January 1979. The experiment
consisted of a collection of collimated sodium iodide scintillators, two of
which the Low Energy detectors (LED, LED-3 and LED-6), were optimized for the
lower energy part of the hard X-ray range between 13 to 180 keV. The first
6-months of mission were dedicated to an all-sky scan after which a pointing
phase started. In pointing mode the A4-LED instrument look axis was kept in a
1 deg dead band centered on the target position. Instead in the "ping-pong"
mode the look axis was regularly alternated with a secondary target a few
degrees away, usually for background determination. This database table
accesses the spectra (and associated files) obtained from the A4-LED
detectors in the ping-pong mode.
