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HEAO-1

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Introduction

HEAO-1 was the first of three spacecraft in NASA's High Energy Astronomy Observatory program. It was designed to survey the entire sky for x-ray emission in the energy range from 0.1 keV to 10 MeV. The second HEAO mission, known as the Einstein satellite, carried the first focusing x-ray telescope, while the third HEAO was dedicated to cosmic ray research and also carried the first non-classified high resolution germanium solid state detectors to search for nuclear lines in the 20 keV to 10 MeV range.

HEAO-1 carried four sets of instruments designated A-1 to A-4. The first three utilized gas proportional counters sensitive in the 0.1-60 keV range and used metal plates, tubes, or wires for collimation. The NRL Large Area Sky Survey instrument (A-1) was composed of 7 modules, each with area of 1600 cm2. Six modules were on one side and one was on the other with the rest of the instruments. The GSFC/CIT Cosmic X-Ray Experiment (A-2) consisted of six detectors optimized for three energy ranges: the Low Energy Detectors (LEDs), the Medium Energy Detectors (MEDs), and the High Energy Detectors (HEDs). Each had an effective area of about 800 cm2. The Harvard/MIT Scanning Modulation Collimator (A-3) was designed to provide accurate positions of strong sources using a wire grid collimator to a few tens of arcseconds. The UCSD/MIT HighEnergy X-ray and Low Energy Gamma-Ray instrument (A-4) used inorganic scintillators of NaI and CsI for detection of higher energy radiation up to 10 MeV.

HEAO-1 was launched on August 12, 1977 from Cape Canaveral, Florida on an Atlas-Centaur into a circular orbit 420 km high and with an inclination of 23o to the equator, and with a period of about 93 minutes. It operated normally until January 9, 1979, when the hydrazine fuel used for attitude control ran out. The satellite re-entered the atmosphere on March 12, 1979.

Spacecraft

The HEAO-1 spacecraft was developed by TRW, Inc. of Redondo Beach, CA and was roughly cylindrical, about 6 meters long and 2 meters in diameter. It had a mass of 2700 kilograms, and its attitude was controlled by hydrazine jets to provide a constant spin rate of 3 revolutions per orbit, or about 31 minutes.

HEAO-1 Clean smThe spin axis direction was held within 1/2o of the solar direction by stepping the spin direction by 1/2o twice a day. In this manner the scanning instruments would complete a full scan of the entire sky every six months. During the 1.5 years of the mission, the instruments completed almost three complete sky scans. The spin would be stopped to make a long term pointed observation of a given object infrequently at first and more numerously later in the mission.

The solar panels provided 460 Watts of 28 volt power, and the instruments produced digital data at the rate of 6.4 kilobits/second that was recorded on tape recorders. This data was dumped to the ground stations around the world that were part of the NASA ground segment.

Hard X-ray and Low Energy Gamma-Ray Expt. (A-4)

To cover the wide energy band of 10 keV to 10 MeV, the HEAO A-4 instrument had seven actively shielded NaI(Tl)/CsI(Na) scintillation detectors in a phoswich configuration of three types. The detector types were optimized for subintervals of this energy range: the aperture widths, detector areas and thicknesses were chosen to balance energy dependent considerations of stopping gamma-rays, minimizing background, and avoiding source confusion.

HEAO-1 Instruments smThe two Low Energy Detectors (LEDs), four Medium Energy Detectors (MEDs), and the lone High Energy Detector (HED) had effective areas ranging from 40 cm2 to 120 cm2, with fields of view of 1.2o x 20o, 17o circular, and 37o circular.

Other detectors within the instrument included seven the thick active CsI(Na) shield segments, an NE102 plastic scintillator aperture shield, and the three NE102 particle monitors. The use of a dense material with high atomic number, such as these inorganic scintillators, allowed useful detection efficiency for photons with energy up to 10 MeV, which is impossible for proportional counters at atmospheric pressures. A moveable CsI(Na) active scintillator shutter resided on top of the aperture shield and could be placed above any detector for measurement of internal background.

The active anticoincidence shield counters were used to reduce the background counting rate due to ambient charged particles and photons. The aperture shield consisted of a thin (<1 cm) sheet of plastic scintillator, sufficient to detect charged particles, but transparent to photons with energy above 10 keV.

Publications

--- 1972 ---

Peterson, L.E. 1972, "The High Energy Astronomical Observatory", Sci. & Tech., 28, 213.

--- 1974 ---

Matteson, J.L., Pelling, R.M., & Peterson, L.E. 1974, "The UCSD/MIT Hard X-ray and Low Energy Gamma-Ray Experiment for HEAO-A", Proceedings of the 9th ESLAB Symposium on the Context and Status of Gamma-Ray Astronomy, ESRO SP-106, ???.

--- 1975 ---

Peterson, L.E. 1975, "The Instrumental Techniques in X-Ray Astronomy", Ann. Rev. Astron. Astrophys., 13, 423.

--- 1978 ---

Hoffman, J.A., Wheaton, W.A., Primini, F.A., Campbell, P., Dobson, C.A., Howe, S.K., Tsiang, E.Y., Scheepmaker, A., Lewin, W.H.G., Matteson, J.L., Gruber, D.E., Peterson, L.E., Swank, J.H., Boldt, E.A., Rothschild, R.E., & Serlemitsos, P.J. 1978, "HEAO-1 Observations of X-Ray Bursts from MXB 1730-335", Nature, 276, 587.

Matteson, J.L. 1978, "UCSD/MIT Hard X-ray and Low Energy Gamma-Ray Experiment for HEAO-1: Design and Early Results", Proceedings of the AIAA 16th Aerospace Meeting, Huntsville, AL, Paper 78-35.

--- 1979 ---

Primini, F.A., Cooke, B.A., Dobson, C.A., Howe, S.K., Scheepmaker, A., Wheaton, W.A., Lewin, W.H.G., Baity, W.A., Gruber, D.E., Matteson, J.L., & Peterson, L.E. 1979, "HEAO-1 Observations of High Energy X-Rays from 3C273", Nature, 278, 234.

Wheaton, W.A., Doty, J.P., Primini, F.A., Cooke, B.A., Dobson, C.A., Goldman, A., Hecht, M., Hoffman, J.A., Howe, S.K., Sheepmaker, A., Tsiang, E.Y., Lewin, W.H.G., Matteson, J.L., Gruber, D.E., Baity, W.A., Rothschild, R.E., Knight, F.K., Nolan, P., & Peterson, L.E. 1979, "Discovery of a Pulsed Absorption Feature in the Hard X-Ray Spectrum of 4U0115+63", Nature, 282, 240.

Hoffman, J.A., Lewin, W.H.G., Primini, F.A., Wheaton, W.A., Swank, J.H., Boldt, E.A., Holt, S.S., Serlemitsos, P.J., Share, G.H., Wood, K., Yentis, D., Evans, W.D., Matteson, J.L., Gruber, D.E., & Peterson, L.E. 1979, "HEAO-1 Observation of a Type I Burst from MXB 1728-34", Ap. J. (Letters), 233, L51.

Matteson, J.M., Gruber, D.E. & Hoffman, J.A. 1979, "HEAO-1 Observations of Her X-1 at Energies Above 13 keV in February 1978", Gamma-Ray Spectroscopy in Astrophysics, eds. Cline, T. & Ramaty, R., NASA T.M. 79619.

Baity, W.A., Gruber, D.E., Matteson, J.L., Knight, F.K., Nolan, P.L., Scheepmaker, A., Wheaton, W.A., Hoffman, J.A., Primini, F.A., Lewin, W.H.G., & Peterson, L.E. 1979, "High-Energy X-Ray Observations of Extragalactic Objects", Adv. Space Res.: X-Ray Astronomy, eds. Baity, W.A. & Peterson, L.E., (Pergamon: Oxford), 3, 373.

Matteson, J.L., Gruber, D.E., Rothschild, R.E., & Hoffman, J.A. 1979, "HEAO-1 Observations of Her X-1 at Energies Above 13 keV in February 1978", Adv. Space Res.: X-Ray Astronomy, eds. Baity, W.A. & Peterson, L.E., (Pergamon: Oxford), 3, 493.

Matteson, J.L., Nolan, P.L., & Peterson, L.E. 1979, "A Search for Gamma-Ray Lines from the Galactic Center by HEAO-1", Adv. Space Res.: X-Ray Astronomy, eds. Baity, W.A. & Peterson, L.E., (Pergamon: Oxford), 3, 543.

Hudson, H.S. 1979, "Observations of Particle Acceleration in Solar Flares", Workshop on Particle Acceleration Mechanisms in Astrophysics, eds. Arons, J.A. & McKee, C., (AIP: New York), 115.

Levine, A. 1979, "High Energy X-Ray Results from HEAO-1: X-Ray Pulsars and the All Sky Survey", HEAO-1 Science Symposium, Huntsville, AL, NASA CP-2113, 140.

Matteson, J.L. 1979, "Hard X-ray Observations from HEAO-1", HEAO-1 Science Symposium, Huntsville, AL, NASA CP-2113, 166.

Pelling, M. 1979, "Hard X-ray Observations from HEAO-1", Symposium on the Results and Future Prospects of X-ray Astronomy, Tokyo, 194.

Rothschild, R.E. 1979, "The 178th Meeting of the High Energy Astrophysics Division of the American Astronomical Society", Earth & Extraterrestrial Sci., 3, 189.

--- 1980 ---

Rothschild, R.E., Gruber, D.E., Knight, F.K., Nolan, P.L., Soong, Y., Levine, A.M., Primini, F.A., Wheaton, W.A., & Lewin, W.H.G. 1980, "A High Sensitivity Determination of the Hard Spectrum of Sco X-1", Nature, 286, 786.

Hudson, H.S., Bai, T., Gruber, D.E., Matteson, J.L., Nolan, P.L., & Peterson, L.E. 1980, "HEAO-1 Observations of Gamma-Ray Lines from a Solar Flare", Ap. J. (Letters), 236, L91.

Bai, T. 1980, "On the X-Ray Continuum and Iron Line Emission of the Low State of Hercules X-1", Ap. J., 239, 328.

Bai, T. 1980, "Implications of the High-State Iron-Line Feature and Soft X-Ray Emission of Hercules X-1", Ap. J., 239, 999.

Gruber, D.E., Matteson, J.L., Nolan, P.L., Knight, F.K., Baity, W.A., Rothschild, R.E., Peterson, L.E., Hoffman, J.A., Sheepmaker, A., Wheaton, W.A., Primini, F.A., Levine, A.M., & Lewin, W.H.G. 1980, "Her X-1 Hard X-ray Pulsations Observed from HEAO-1", Ap. J. (Letters), 240, L127.

--- 1981 ---

Nolan, P.L., Gruber, D.E., Knight, F.K., Matteson, J.L., & Rothschild, R.E. 1981, "The Hard X-Ray Spectrum of Cygnus X-1", Nature, 293, 275.

Primini, F.A., Basinska, E., Howe, S.K., Lang, F., Levine, A.M., Lewin, W.H.G., Rothschild, R.E., Baity, W.A., Gruber, D.E., Matteson, J.L., Lea, S.M., & Reichart, G.A. 1981, "HEAO-1 Observations of the Perseus Cluster above 10 keV", Ap. J. (Letters), 243, L13.

Bai, T. 1981, "The 35 Day Dependence of the Pulse Shape of Hercules X-1", Ap. J., 243, 244.

Baity, W.A., Rothschild, R.E., Lingenfelter, R.E., Stein, W.A., Nolan, P.L., Gruber, D.E., Knight, F.K., Matteson, J.L., Peterson, L.E., Primini, F.A., Levine, A.M., Lewin, W.H.G., Mushotzky, R.F., & Tennant, A.F. 1981, "Cen A (NGC 5128) at 2 keV - 2.3 MeV: HEAO-1 Observations and Implications", Ap. J., 244, 429.

Lang, F.L., Levine, A.M., Bautz, M., Hauskins, S., Howe, S., Primini, F.A., Lewin, W.H.G., Baity, W.A., Knight, F.K., Rothschild, R.E., & Petterson, J. 1981, "Discovery of a 30-Day Periodicity in LMC X-4", Ap. J. (Letters), 246, L21, and Erratum, Ap. J. (Letters), 296, L21.

Lea, S.M., Reichert, G.A., Mushotzky, R.F., Baity, W.A., Gruber, D.E., Rothschild, R.E., & Primini, F.A. 1981, "HEAO-1 High Energy X-Ray Observations of the Virgo Cluster and A2142", Ap. J., 246, 369.

Nolan, P.L., Gruber, D.E., Matteson, J.L., Peterson, L.E., Rothschild, R.E., Doty, J.P., Levine, A.M., Lewin, W.H.G., & Primini, F.A. 1981, "Rapid Variability of 10-140 keV X-Rays from Cygnus X-1", Ap. J., 246, 494.

Byrne, P.F., Levine, A.M., Bautz, M., Howe, S.K., Lang, F.R., Primini, F.A., Lewin, W.H.G., Gruber, D.E., Knight, F.K., & Nolan, P.L. 1981, "High Energy X-ray Observations of the 38 Second Pulsar", Ap. J., 246, 951.

Worrall, D.M., Knight, F.K., Nolan, P.L., Rothschild, R.E., Levine, A.M., Primini, F.A., & Lewin, W.H.G. 1981, "The Hard X-Ray Spectrum of X Persei", Ap. J. (Letters), 247, L31.

Dil, S., Primini, F.A., Basinska, E., Bautz, M., Howe, S.K., Lang, F., Levine, A.M., Lewin, W.H.G., Worrall, D., Nolan,P., and Matteson, J.L. 1981, "HEAO-1 Observations of High Energy X-Rays from the Seyfert I Galaxy Mkn 501", Ap. J, 250, 513.

Rothschild, R.E., Gruber, D.E., Knight, F.K., Matteson, J.L., Nolan, P.L., Swank, J., Holt, S.S., Serlemitsos, P.J., Mason, K., & Touhy, I. 1981, "HEAO-1 Observations of the X-Ray Spectrum of AM Her from 0.1 to 150 keV", Ap. J., 250, 723.

Knight, F.K., Matteson, J.L., & Peterson, L.E. 1981, "The Spectra of Two Gamma-Ray Bursts", Astrophys. Space Sci., 75, 21.

Nolan, P.L., Doty, J.P., Gruber, D.E., Levine, A.M., Matteson, J.L., Peterson, L.E., Primini, F.A., & Rothschild, R.E. 1981, "Rapid Variability of 10-140 keV X-Rays from Cygnus X-1", Adv. Space Res.: High Energy Astrophysics, ed. Hudson, H.S., (Pergamon: Oxford), 1, 215.

Hudson, H.S. 1981, "X-ray and Gamma-Ray Observations of a White Light Flare", Adv. Space Res.: High Energy Astrophysics, ed. Hudson, H.S., (Pergamon: Oxford), 1, 247.

--- 1982 ---

Gorecki, A., Levine, A., Bautz, M., Lang, F., Primini, F.A., Lewin, W.H.G., , Baity, W.A., Gruber, D.E., & Rothschild, R.E. 1982, "HEAO-1 Observations of the Long-Term Variability of Hercules X-1", Ap. J., 256, 234.

Knight, F.K. 1981, "Observations and Interpretations of the Pulsed Emission from the Crab Pulsar", Ap. J., 538, 538.

Knight, F.K., Matteson, J.L., Peterson, L.E., & Rothschild, R.E. 1982, "X-Ray and Gamma-Ray Upper Limits for Pulsed Emission from Radio Pulsars", Ap. J., 260, 553.

Levine, A.M. & Jernigan, J.G. 1982, "On the Orbital Phase Dependence of the Turn-On Times of Hercules X-1", Ap. J., 262, 294.

Nolan, P.L., Gruber, D.E., Matteson, J.L., Peterson, L.E. Knight, F.K., Levine, A.M., Lewin, W.H.G., and Primini, F.A. 1982, "Observations of 12-2000 keV X-Rays from GX 339-4", Ap. J., 262, 727.

Lingenfelter, R.E. & Ramaty, R. 1982, "On the Origin of the Positron Annihilation Radiation from the Direction of the Galactic Center", Workshop on the Galactic Center, eds. Riegler, G.R. & Blandford, R.D., Pasadena, CA, (AIP: New York), ???.

Matteson, J.L. 1982, "Observations of Continuum X-ray and Gamma-Ray Emission from the Galactic Center", Workshop on the Galactic Center, eds. Riegler, G.R. & Blandford, R.D., Pasadena, CA, (AIP: New York), ???.

Hueter, G.J. & Gruber, D.E. 1982, "An Absorption Feature in the Spectrum of a Gamma Ray Burst on March 25, 1978", Accreting Neutron Stars, eds. Brinkmann, W. & Trumper, J., (MPI: Munich), Munich, 213.

Gruber, D.E. & Primini, F.A. 1982, "Hard X-Ray Observations of Fast Pulsars from HEAO-1", Accreting Neutron Stars, eds. Brinkmann, W. & Trumper, J., (MPI: Munich), Munich, 41.

--- 1983 ---

Nolan, P.L., Lingenfelter, R.E., & Matteson, J.L. 1983, "A Feature in the X-Ray Spectrum of Cygnus X-1: A Possible Positron Annihilation Line", Ap. J., 265, 389.

Bautz, M., Howe, S., Gorecki, A., Lang, F., Levine, A., Primini, F., & Lewin, W.H.G. 1983, "High Energy X-Ray Observations of Vela X-1", Ap. J., 266, 794.

Rothschild, R.E., Mushotzky, R.F., Baity, W.A., Gruber, D.E., Matteson, J.L., & Peterson, L.E. 1983, "2-165 keV Observations of Active Galaxies and the Diffuse Background", Ap. J., 269, 423.

Howe, S.K., Primini, F.A., Bautz, M.W., Lang, F.L., Levine, A.M., & Lewin, W.H.G. 1983, "HEAO-1 High Energy Observations of Centaurus X-3", Ap. J., 272, 678.

Soong, Y. & Rothschild, R.E. 1983, "Long-term Hard X-Ray Observations of Scorpius X-1 from HEAO-1", Ap. J., 274, 327.

Wilson, C. & Rothschild, R.E. 1983, "Observations of a Hard X-ray Component in the Spectrum of Nova Ophiuchi", Ap. J., 274, 717.

Proctor, R.J. 1983, "Temporal Aperture Modulation", Workshop on X-ray Astronomy and Spectroscopy, ed. Holt, S.S., Greenbelt, MD, NASA T.M. 83848, 335.

Matteson, J.L. 1983, "Spectroscopy in the 10 keV to 10 MeV Range", Workshop on X-ray Astronomy and Spectroscopy, ed. Holt, S.S., Greenbelt, MD, NASA T.M. 83848, 549.

Rothschild, R.E. 1983, "Hard X-ray Astrophysics", Workshop on X-ray Astronomy and Spectroscopy, ed. Holt, S.S., Greenbelt, MD, NASA T.M. 83848, 599.

Hueter, G.J., Hudson, H.S., Matteson, J.L., Rothschild, R.E., & Peterson, L.E. 1983, "Observation of an Absorption Feature in a Gamma Ray Burst Spectrum", Proceedings of the 18th International Cosmic Ray Conference, 1, 95.

Lingenfelter, R.E., & Hueter, G.J. 1983, "A Distance Model for Gamma Ray Bursts", Proceedings of the 18th International Cosmic Ray Conference, 1, 54.

Hueter, G.J. & Lingenfelter, R.E. 1983, "A Fireball Model for the March 25, 1978 Gamma Ray Burst", Positron-Electron Pairs in Astrophysics, eds. Burns, M.J., Harding, A.X., & Ramaty, R., (AIP:New York), 89.

--- 1984 ---

Rothschild, R.E. & Lingenfelter, R.E. 1984, "A 164-Day Period in Gamma-Ray Bursts from GBS 0526-66?", Nature, 312, 737.

Baity, W.A., Mushotzky, R.F., Worrall, D.M., Rothschild, R.E., Tennant, A.F., and Primini, F.A., "Observations of NGC 4151 at 2 keV-2 MeV from HEAO-1", Ap. J., 279, 555.

Gruber, D.E. & Rothschild, R.E. 1984, "HEAO-1 Observations of Variability of SMC X-1", Ap. J., 283, 546.

Cooke, B.A., Levine, A., Lang, F.L., Primini, F.A., & Lewin, W.H.G., "HEAO-1 High Energy X-Ray Sources: H1705-250 (Nova Ophiuchi), H1743-322, and H1833-077 (Scutum X-1)", Ap. J., 285, 258.

Levine, A.M., Lang, F., Lewin, W.H.G., Primini, F.A., Dobson, C.A., Doty, J., Hoffman, J.A., Howe, S.K., Scheepmaker, A., Wheaton, W.A., Matteson, J.L., Baity, W.A., Gruber, D.E., Knight, F.K., Nolan, P.L., Pelling, R.M., Rothschild, R.E., & Peterson, L.E. 1984, "The HEAO-1 (A4) Catalog of High Energy X-Ray Sources", Ap. J. (Supplements), 54, 581.

Gruber, D.E. 1984, "SMC X-1: Another Tilted Precessing Accretion Disk?", High Energy Transients in Astrophysics, ed. Woosley, S.E., (AIP: New York), 150.

Hueter, G.J. 1984, "Observations of an Absorption Feature in a Gamma Ray Burst Spectrum", High Energy Transients in Astrophysics, ed. Woosley, S.E., (AIP: New York), 373.

Baity, W.A., Hueter, G.J., & Lingenfelter, R.E. 1984, "A Catalog and Bibliography of Gamma Ray Bursts", High Energy Transients in Astrophysics, ed. Woosley, S.E., (AIP: New York), 434.

Lingenfelter, R.E., & Hueter, G.J. 1984, "Gamma Ray Burst Emission: A Jet and Fireball Model", High Energy Transients in Astrophysics, ed. Woosley, S.E., (AIP: New York), 558.

Gruber, D.E., Rothschild, R.E., Matteson, J.L., & Kinzer, R.L. 1984, "The HEAO-1 Diffuse Component Spectrum from 15 keV to Above 500 keV", X-Ray and UV Emission from Active Galactic Nuclei, eds. Brinkmann, W. & Trumper, J., (MPI: Garching), MPE Report 184, 129.

--- 1985 ---

Hueter, G.J. & Matteson, J.L. 1985, "HEAO-1 Observations of Gamma Ray Bursts", Proceedings of the 19th International Cosmic Ray Conference, 1, 1.

Knight, F.K., Matteson, J.L., Jung, G.V., & Rothschild, R.E. 1985, "Spectra and Positions of Galactic Gamma-Ray Sources", Proceedings of the 19th International Cosmic Ray Conference, 1, 217.

Gruber, D.E. Matteson, J.L., Jung, G.V., & Kinzer, R. 1985, "Spectrum of the Gamma-Ray Diffuse Component Observed from HEAO-1", Proceedings of the 19th International Cosmic Ray Conference, 1, 349.

--- 1987 ---

Rothschild, R.E. & Soong, Y. 1987, "Two Binary Cycles of GX 301-2", Ap. J., 315, 154.

Soong, Y., Gruber, D.E., & Rothschild, R.E. 1987, "A Rapid Change of the Hercules X-1 Pulse Profile and High-State Duration", Ap. J. (Letters), 319, L77.

Rephaeli, Y., Gruber, D.E., & Rothschild, R.E. 1987, "HEAO-1 Hard X-ray Observations of Three Abell Clusters of Galaxies", Ap. J., 320, 139.

Rothschild, R.E., Staubert, R., Brinkman, W., Pederson, H., Parmar, A.N., Hueter, G.J., Lingenfelter, R.E., Collmar, W., Kendziorra, E., and Brunner, H. 1987, "EXOSAT Observations of the 5 March 1979 Gamma-Ray Burst Source Position (GBS 0526-66)", Astro. Lett. and Comm., 25, 173.

--- 1988 ---

Gruber, D.E. 1988, "The Very Low Frequency Power Spectrum of Cen X-3", Ap. J., 328, 265.

Schmidt, M., Higdon, J.C., & Hueter, G. 1988, "Application of the V/V MAX Test to Gamma-Ray Bursts", Ap. J. (Letters), 329, L85.

Rephaeli, Y. & Gruber, D.E. 1988, "HEAO-1 Hard X-Ray Observations of Clusters of galaxies and Intracluster Magnetic Fields", Ap. J., 333, 133.

Bezler, M., Gruber, D.E., & Rothschild, R.E. 1988, "Upper Limits from Hard X-Ray Observations of Five Bl Lacertae Objects", Ap. J., 334, 995.

Gruber, D.E., Soong, Y., & Rothschild, R.E. 1988, "A Rapid Change to Double Pulsing in Her X-1", Adv. Space Res., 8, 503.

Soong, Y., Gruber, D.E., & Rothschild, R.E. 1988, "The Temporal-Spectral Behavior of Hercules X-1", Physics of Neutron Stars and Black Holes, ed. Tanaka, Y., (Universal Academy: Tokyo), 79.

--- 1989 ---

Jung, G.V. 1989, "The Hard X-Ray to Low Energy Gamma-Ray Spectrum of the Crab Nebua", Ap. J., 338, 972.

Gruber, D.E., Jung, G.V., & Matteson, J.L. 1989, "Radioactivity Observed in Scintillation Counters During the HEAO-1 Mission", Proceedings of the Conference on High Energy Radiation Background in Space", eds. Rester, C.& Trombka, J., (AIP: New York), 232.

Peterson, L.E., Gruber, D.E., Jung, G.V., & Matteson, J.L. 1989, Proceedings of the 21st International Cosmic ray Conference, 1, 44.

--- 1990 ---

Soong, Y., Gruber, D.E., Peterson, L.E., & Rothschild, R.E. 1990, "Temporal Behavior of Hercules X-1: The Long Term Variability of its Pulse Profile and the 35d X-Ray Intensity Modulation", Ap. J., 348, 634.

Soong, Y., Gruber, D.E., Peterson, L.E., & Rothschild, R.E. 1990, "Spectral Behavior of Hercules X-1: Its Long Term Variability and Pulse Phase Spectroscopy", Ap. J., 348, 641.

Soong, Y., Gruber, D.E., Rothschild, R.E., & Peterson, L.E. 1990, "15-100 keV Variability in Her X-1 Observed by HEAO-1", Adv. Space Res., 10, 99.

Collmar, W. & Gruber, D.E. 1990, "Correlations Between X-Ray Luminosity and Pulse Shape And Spectral Shape in Binary X-Ray Pulsars", Proceedings of the 23rd ESLAB Symposium, ???, ESA SP-296, 353.

--- 1991 ---

Petterson, J.A., Rothschild, R.E., & Gruber, D.E. 1991, "A Model for the 35 Day Variations in the Pulse Profile of Hercules X-1", Ap. J., 378, 696.

Rephaeli, Y., Gruber, D.E., Persic, M., & MacDonald, D. R. 1991, "X-Ray Emission from Starburst Galaxies", Ap. J. (Letters), 380, L59.

Gruber, D.E. & Briggs, M.S. 1991, "Observation of Annihilation Radiation from the Galactic Center: The Point and Ridge Components", Gamma-Ray Line Astrophysics, eds. Durouchoux, P. & Prantos, N., (AIP: New York), 58.

--- 1992 ---

Gruber, D.E. 1992, "The Hard X-Ray Background", Proceedings of the International Workshop on the X-Ray Background, eds. Barcons, F.X. & Fabian, A., (???), 41.

Briggs, M.S., Matteson, J.L., Gruber, D.E., & Peterson, L.E. 1992, "Observations of Galactic Positron Annihilation Radiation", Proceedings of the 22nd International Cosmic ray Conference, 2, 153.

Gruber, D.E., Rephaeli, Y., & Persic, M. 1992, "HEAO Study of Hard X-Ray Emission from Starburst Galaxies", Proceedings of the International Workshop on the X-Ray Background, eds. Barcons, F.X. & Fabian, A., (???), 169.

--- 1993 ---

Briggs, M.S., Gruber, D.E., Matteson, J.L., & Peterson, L.E. 1993, "A Transient MeV Range Gamma-Ray Source Observed by HEAO-1", Proceedings of the 2nd Compton Symposium, eds. ??? & ???, (AIP: New York), 304.

--- 1995 ---

Briggs, M.S., Gruber, D.E., Matteson, J.L., & Peterson, L.E. 1995, "Discovery of a Transient MeV Range Gamma-Ray Source", Ap. J., 442, 638.

--- 1997 ---

Kinzer, R., Jung, G.V., Gruber, D.E., Matteson, J.L., & Peterson, L.E. 1997, "Diffuse Cosmic Gamma Radiation Measured by HEAO-1", Ap. J., 475, 361.

Ph. D. Theses

F.K. Knight, 1981, UCSD, "X-ray and Gamma-Ray Observations of Pulsed Emission from Radio Pulsars" P.L. Nolan, 1982, UCSD, "Hard X-ray Emission from Galactic Black Hole Candidates" F.L. Lang, 1985, MIT, "The Long Term Intensity Variations of Selected Celestial X-Ray Sources in the Energy range ~13-150 keV" G.V. Jung, 1986, UCSD, "The Hard X-ray to Low Energy Gamma-Ray Spectrum of the Crab Nebula" G.J. Hueter, 1987, UCSD, "HEAO-1 Observations of Gamma-Ray Bursts" Y. Soong, 1988, UCSD, "A Study of Temporal-Spectral Behavior of Hercules X-1"

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