[en] Observations of the binary x-ray sources Cygnus X-1, Cygnus X-3, and Hercules X-1 were performed during two balloon flights on 24 June and 14 July, 1975. Data in the energy range 18 to 200 keV were obtained using an x-ray telescope with 450 cm² of effective area and a 2.9⁰ x 5.8⁰ FWHM field of view

[en] A Nuclear Radiation Monitor incorporating a NaI(Tl) scintillation detector was flown as part of the verification flight instrumentation on the Spacelab 2 mission, July 29 to August 6, 1985. Gamma-ray spectra were measured with better than 20 s resolution throughout most of the mission in the energy range 0.1 to 30 MeV. Knowledge of the decay characteristics and the geomagnetic dependence of the counting rates enable measurement of the various components of the Spacelab gamma-ray background: prompt secondary radiation, Earth albedo, and delayed induced radioactivity. The status of the data analysis and present relevant examples of typical background behavior are covered

[en] The NASA/Goddard Space Flight Center Low Energy Gamma ray Spectrometer (LEGS) observed the nearby active nucleus galaxy Centaurus A (NGC 5128) during a balloon flight on 1981 November 19. There is no evidence of a break in the spectrum or of any line features. The 1.6 MeV limit is a factor of 8 lower than the 1974 line flux, indicating that, if the 1974 feature was real, and, if it was narrow, then the line intensity decreased significantly between 1974 and 1981. The lack of observed annihilation radiation from Cen A, combined with the temporal variations that are seen in the X-ray and gamma-ray intensities, constrain the size of the emission region to be between 10 to the 13th power and 5 x 10 to the 17th power cm

[en] Observations of Cyg X-1 with a 20 to 200 keV balloon carried x-ray telescope in 1969, 1970, and 1972 are presented. These results reveal the following characteristics of Cyg X-1: The steep spectrum observed at E less than 10 keV during the ''radio quiet'' phase can extend to 200 keV. This phase may have lasted 21 months (July 1969 to March 1971). The flux at 30 keV can vary from 1.1 x 10^-2 to 1.4 x 10^-3 ph (cm²-sec-keV)^-1 and that at 100 keV from 1.4 x 10^-3 to 10^-4. The low flux values are factors of 3 and 8 below the ''normal'' values at 30 and 100 keV respectively, are rarely observed, and may be associated with the early phase of the 1971 April x-ray transition. During some one hour periods the intensity remained constant to approximately 20% and during other periods it varied a factor 2 in 5 minutes and a factor 10 in 1 hour. Complex spectral variations accompanied the intensity changes

[en] The GSFC Low-Energy Gamma-Ray Spectrometer observed the region of the galactic center during a balloon flight from Alice Springs, Australia, on 1981 November 20. No significant excess over background was evident in the 511 keV annihilation line. A 98 percent confidence upper limit is derived for this line of 1.2 x .001 photons/sq. cm-s. Continuum emission was detected above 100 keV with a best-fitting power law spectrum

[en] Two-dimensional maps of the 22-64 keV emission from the Crab Nebula with an angular resolution of 15 arcsec has been synthesized. The maps are generated by application of a maximum entropy method operating on a series of one-dimensional scans obtained with a balloon-borne modulation collimator telescope. The two-dimensional size, shape and orientation of the hard X-ray nebula relative to the pulsar have been measured for the first time. The implications of these results for models of electron transport in the Crab are discussed, and the geometry of the observed X-ray nebula is related to other features of the Crab Nebula system. 63 references

[en] 3U 1207 + 39, the X-ray source identified with the Seyfert galaxy NGC 4151, was observed on 1975 June 24 with a balloon-borne telescope. The photon number spectrum was relatively flat (power-law slope α = -1.6 +- 0.9) and consistent with previous observations. Thermal bremsstrahlung models provide poorer fits to the data. (author)

[en] The hard X-ray spectrum of HER X-1 was measured for the first time with a high resolution (1.4 keV FWHM) germanium spectrometer. The observation was performed near the peak of the on-state in the 35 day cycle and the 1.24 pulsations were observed between the energies of 20 keV and 70 keV. The feature corresponds to an excess of 7.5 sigma over the low energy continuum. Smooth continuum models are poor fits to the entire energy range (chance probabilities of 2 percent or less). The best fit energies are 35 keV for an absorption line and 39 keV for an emission line. These are significantly lower energies than those derived from previous experiments. A direct comparison of our data with the results of the MPI/AIT group shows statistically significant variations which strongly suggest variability in the source

[en] The NASA Goddard Space Flight Center Low-Energy Gamma-Ray Spectrometer observed the region of the galactic center during a balloon flight from Alice Springs, Australia on 1981 Novmeber 20. No significant excess over background was evident in the 511 keV annihilation line. We derive a 98% confidence upper limit for this line of 1.2 x 10^-3 photons cm^-2 s^-1. Continuum emission was detected above 100 keV with a best fitting power-law spectrum of the form dN/dE = A/E/100)^-alpha, where A = (1.9 +- 0.4) x 10^-4 photons cm^-2 s^-1 keV^-1 and α = 2.35^+0.5sub -0.4/. These results confirm the recent observations of time variability by HEAO 3 (Riegler et al.). A compact source at or near the galactic center provides the most satisfactory agreement with all of the data

[en] The design and performance of a phoswich type scintillation detector system is discussed having 34 cm² effective collecting area and a sensitivity of 3x10^-5 photons cm^-2 s^-1 keV^-1 for balloon-borne cosmic X-ray source observations. The various shield anticoincidence systems are evaluated for effectiveness in reduction of the system background. The total background of nominally 4x10^-4 counts cm^-2 s^-1 keV^-1 is analyzed and found to consist of aperture flux, K-escape X-rays from the shielding, leakage and degradation of gamma-rays through the shielding, and several particle induced effects. The background analysis suggests an ultimate practical upper limit of about 8x10^-5 counts cm^-2 s^-1 keV^-1 might be attainable beyond which further sensitivity improvements will require increased collecting area or a basically differing design approach. (Auth.)