The Gamma-Ray Spectrometer (GRS) was one of two instruments on the Solar Maximum Mission (SMM) which independently monitored cosmic gamma-ray bursts from SMM's launch in February 1980 until the end of the mission in 1989. The GRS was designed for investigation of the gamma-ray spectrum of solar flares (Forrest, D.J. et al. 1980, Sol. Phys., 65, 15). The main detector was an array of seven gain-controlled 7.6 cm diameter X 7.6 cm thick NaI(Tl) detectors. A complete spectrum was obtained every 16.38 seconds in the energy range 0.3-9 MeV. The number of counts in three energy windows covering the 4.2-6.4 MeV range was read out every 2.048 seconds. In addition, the number of counts in an approximately 50 keV wide window near 300 keV was read out every 64 milliseconds. The spectrometer was shielded by a 2.5 cm thick CsI(Na) annulus and a 25 cm diameter X 7.6 cm thick CsI(Na) back detector. The shield elements defined a field of view of approximately 135 degrees (FWHM) in the solar direction. The CsI back detector and the seven NaI detectors together provided a high-energy spectrometer with approximately 100 cm<sup>2</sup> effective area and four energy channels from 10 to 100 MeV. The number of counts in those high-energy channels was read out every 2.048 seconds. The experiment was complemented by two 8 cm<sup>2</sup> X 0.6 cm thick NaI(Tl) detectors which measured the X-ray portion of the spectrum every 1.024 seconds in the range from 13 keV to 182 keV. This database table was created by the HEASARC in the early 1990s based on tables supplied by the SMM Project and was subsequently revised in February 2002. This is a service provided by NASA HEASARC .
This table records high-level information for the observations obtained with HaloSat and provides access to the HaloSat data archive. HaloSat is the first astrophysics-focused CubeSat funded by NASA's Astrophysics Division (PI P. Kaaret, University of Iowa). HaloSat is designed to map soft X-ray oxygen line emissions across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. HaloSat was launched from the NASA Wallops Flight Facility and delivered to the International Space Station on May 21, 2018. HaloSat was deployed into orbit on July 13, 2018. The spacecraft and science instrument commissioning phase ended on October 16, 2018, and science operations started after that. Initially approved to operate for 12 months, HaloSat successfully collected science data from October 15, 2018, until September 29, 2020, effectively doubling the mission lifetime. HaloSat reentered Earth's atmosphere on January 4, 2021. To trace the Galactic halo, HaloSat is equipped with a non-focusing instrument, comprised of three independent silicon drift detectors (SDD14, SDD38, SDD54) operating in the energy range of 0.4 - 7.0 keV with a field of view of 10 deg in diameter and an energy resolution of 84.8 +/- 2.7 eV at 677 eV and 137.4 +/- 0.9 eV at 5895 eV. The observing strategy was to divide the sky into 333 positions (HaloSat fields) and acquire a minimum of 8000 detector-seconds for each position throughout the initial 12 months of operations. After launch, additional positions were added to the initial 333 positions. HaloSat observations of the chosen fields are divided in intervals of time such that the data files do not exceed 2GB. Each observation is labeled with a sequence number. This database table contains one record for each sequence number and includes parameters related to the observation. The contents of this database table are generated at the HEASARC using information from the data files. The table was last updated in April 2023. This is a service provided by NASA HEASARC .
This table records the start and stop times of the uninterrupted observation intervals obtained by the three detectors on board of HaloSat and provides access to the HaloSat observations containing these intervals. HaloSat is the first astrophysics-focused CubeSat funded by NASA's Astrophysics Division (PI P. Kaaret, University of Iowa). HaloSat is designed to map soft X-ray oxygen line emissions across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. HaloSat was launched from the NASA Wallops Flight Facility and delivered to the International Space Station on May 21, 2018. HaloSat was deployed into orbit on July 13, 2018 and collected science data from October 15, 2018, until September 29, 2020. HaloSat reentered Earth's atmosphere on January 4, 2021. To trace the Galactic halo, HaloSat is equipped with a non-focusing instrument, comprised of three independent silicon drift detectors (SDD14, SDD38, SDD54) operating in the energy range of 0.4 - 7.0 keV with a field of view of 10 deg in diameter and an energy resolution of 84.8 +/- 2.7 eV at 677 eV and 137.4 +/- 0.9 eV at 5895 eV. The HaloSat data are divided by specific positions in the sky and labeled with a number, the sequence number. Each sequence number contains all data for a specific sky position collected during the HaloSat operations therefore each observation contains time intervals that may be apart day, week or months. This database table instead has in each record the start and stop times of one uninterrupted time interval of good data for a specific detector. This table therefore enables searches of the HaloSat data for a specific time event detected by different obsevatories. The contents of this database table are generated at the HEASARC using information from the data files. The table was created in April 2023. This is a service provided by NASA HEASARC .
This table is a representation of part of the Hamburg/ROSAT All-Sky Survey (RASS) Catalog (HRC) of optical identifications of X-ray sources at high-galactic latitude, namely the list of proposed and possible optical identifications. (The list of the X-ray sources themselves is given in the linked Browse table HRASSCAT). The HRC includes all X-ray sources from the ROSAT Bright Source Catalog (RASS-BSC) with galactic latitude |b| >= 30 degrees and declination Dec >= 0 degrees. In this part of the sky covering ~10,000 square degrees, the RASS-BSC contains 5341 X-ray sources. For the optical identification, the HRC authors used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC, an identification could be given. For the rest, either no counterpart was visible in the error circle, or a plausible identification was not possible. With ~42%, AGN represent the largest group of X-ray emitters, ~31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only ~4% and ~5%, respectively. In ~3% of the RASS-BSC sources, no object was visible on the blue direct plates within 40" around the X-ray source position. The catalog has been used as a source for the selection of (nearly) complete samples of the various classes of X-ray emitters. This table was produced by the HEASARC in February 2005 based on the CDS Catalog table J/A+A/406/353/optical.dat. This is a service provided by NASA HEASARC .
This table is a representation of part of the Hamburg/ROSAT All-Sky Survey (RASS) Catalog (HRC) of optical identifications of X-ray sources at high-galactic latitude, namely the list of X-ray sources. (The list of proposed and possible optical counterparts is given in the linked Browse table HRASSOPTID). The HRC includes all X-ray sources from the ROSAT Bright Source Catalog (RASS-BSC) with galactic latitude |b| >= 30 degrees and declination Dec >= 0 degrees. In this part of the sky covering ~10,000 square degrees, the RASS-BSC contains 5341 X-ray sources. For the optical identification, the HRC authors used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC, an identification could be given. For the rest, either no counterpart was visible in the error circle, or a plausible identification was not possible. With ~42%, AGN represent the largest group of X-ray emitters, ~31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only ~4% and ~5%, respectively. In ~3% of the RASS-BSC sources, no object was visible on the blue direct plates within 40" around the X-ray source position. The catalog has been used as a source for the selection of (nearly) complete samples of the various classes of X-ray emitters. This table was produced by the HEASARC in February 2005 based on the CDS Catalog table J/A+A/406/353/x-ray.dat. This is a service provided by NASA HEASARC .
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 .
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 .
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 .
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 .
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 .
