- ID:
- ivo://nasa.heasarc/a4
- Title:
- HEAO 1 A4 Catalog of High-Energy X-Ray Sources
- Short Name:
- A4
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/a2led
- Title:
- HEAO 1 A2 LED Catalog
- Short Name:
- A2LED
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a1point
- Title:
- HEAO 1 A1 Lightcurves
- Short Name:
- A1POINT
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a3
- Title:
- HEAO 1 A3 MC LASS Catalog
- Short Name:
- A3
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a2pic
- Title:
- HEAO 1 A2 Piccinotti Catalog
- Short Name:
- A2PIC
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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<sup>-11</sup> erg/cm<sup>2</sup>/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. This table was last revised by the HEASARC in November 2004 when 2 sources (H1257-042 and H1325-020) which had for some reason been omitted from the previous HEASARC version (the provenance of which is somewhat uncertain) were added back in to the table. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a2lcpoint
- Title:
- HEAO 1 A2 Pointed Lightcurves
- Short Name:
- A2LCPOINT
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a2point
- Title:
- HEAO 1 A2 Pointing Catalog
- Short Name:
- A2POINT
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a2rtraw
- Title:
- HEAO 1 A2 Raw Rates
- Short Name:
- A2RTRAW
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a2lcscan
- Title:
- HEAO 1 A2 Scanned Lightcurves
- Short Name:
- A2LCSCAN
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/a4spectra
- Title:
- HEAO 1 A4 Spectra
- Short Name:
- A4SPECTRA
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This is a service provided by NASA HEASARC .
