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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Broad X ray source produces a highly collimated beam of low energy X rays - a beam with 2 to 5 arc minutes of divergence at energies between 1 and 6 keV in less than 5 feet. The X ray beam is generated by electron bombardment of a target from a large area electron gun.
X ray survey of northern sky in 20-100 kev energy range, giving spectra for Cyg X-1, Tau X-1 and Crab nebula
Weak X ray sources at 20-100 Kev photon energies observed during balloon flight, finding hard rays from Ara XR-1 and Nor XR-1
Scorpius XR-1 X ray emission spectra, discussing Fe emission line near 7 kev plasma models, supernova mass and cosmic abundance
X ray spectra of Sco XR-1, Cyg XR-1 and Cyg XR-2 for proton energy range 1.5-13 kev from proportional counter measurements
Experiment to measure hard solar and celestial X rays from OSO-5 in energy range of 15 to 250 keV
OSO 3 satellite observations of diffuse X ray emission from galactic plane, eliminating straight line interpolation of spectrum between 3-10 keV X ray range and 100 MeV energy range
Poor energy resolution and the steeply varying continuum spectrum make it impossible to obtain with proportional counters an unambiguous identification of certain emission features of Sco X-1. For this reason a Bragg crystal spectrometer was constructed. The instrument, flown successfully aboard an Aerobee-170 rocket, scanned the spectral range from 2.4 to 2.9 keV. The spectrometer consists of two large reflecting crystals of synthetic graphite. The results obtained during the flight of the instrument clearly indicate that the Bragg method can yield much higher sensitivity to line emission than can proportional counter methods.
The OSO-H solar X-ray instrument monitors X rays from the sun in the energy range 1-300 keV, as well as the charged particle background. The electronics provide accurate logarithmic pulse-height analysis at the high counting rates expected under flare conditions. A high time resolution mode enables tudy the temporal development of a solar flare.
Report of an observation made with a rocket-borne argon-methane proportional counter, which was equipped with a 'Mylar' window and was sensitive to X rays in the range from 0.2 to 10 keV. During a scan of the galactic plane, the detector passed directly over the location of Cen X-3 at a roll rate of 1 deg per second. An extended minimum of X-ray flux was observed. It is concluded that the anomalous effect is intrinsic to the source.
The galactic ridge is interpreted as a population of intrinsically weak X-ray sources, and calculations are presented of the predicted intensity as a function of scale height and radial gradient. Observations of diffuse galactic X-radiation above 1 keV impose severe constraints on discrete-source interpretations of the galactic-plane excess observed at 0.25 keV.
Spectral measurements of six cosmic gamma-ray bursts in the energy region of 0.1 to 1.2 MeV, made using a semi-omnidirectional X-ray detector on IMP-6 are reported. These measurements confirm the hard X-ray or gamma-ray nature of the bursts, as inferred from the original observations by Klebesadel et al., (1973), and show that their maximum energy release is in this several hundred keV region. Each burst consists of several 1 or 2-second pulses each with the characteristic spectrum of approximately 150-keV exponential, followed by a softer decay. There is no evidence of line structure in this energy region, or for a marked change in the energy spectrum within a given pulse. Event size spectra are estimated for galactic and extragalactic models; the total emission is consistent with present measurements of the diffuse background, and unlikely to account for any spectral feature in the few-MeV region.
The spectrum of the entire Cygnus Loop has been obtained using gas-filled proportional counters and filters flown on a Nike-Aerobee rocket. The results indicate an average spectral temperature of (2.8 plus or minus 0.2) x 1,000,000 K and the presence of excess emission in the energy range from 0.530 to 0.693 keV. If the excess emission originates in a single line at 0.658 keV, the intensity at the earth corresponds to 1.8 plus or minus 0.7 photons per sq cm per sec, or about 10% of the total energy received from the Loop. The spectrum of the entire Loop is found to be attenuated by an average of (4.8 plus or minus 0.2) x 10 to the 20th hydrogen atoms per sq cm.
Spectral measurements of six cosmic gamma-ray bursts ranging in energy from 0.1 to 1.2 MeV are reported. These measurements, obtained by means of a semiomnidirectional X-ray detector on the IMP-6 satellite, confirm the hard X-ray or gamma-ray nature of the bursts, as inferred from the original observations by Klebesadel et al. (1973), and show that their maximum energy release is of this several-hundred keV magnitude.
The occurrence of intense, short bursts of 0.1 to 1.2 MeV cosmic gamma rays, recently found using multiple Vela satellites was confirmed with measurements from the IMP-6 satellite. Observations regarding times of occurrence, photon flux, and temporal and spectral characteristics of the bursts are outlined. In particular, since the IMP-6 instrument incorporates a hard X-ray detector with active particle rejection and full-time omnidirectional particle intensity monitoring, the results fully confirm and establish the hard X-ray or gamma-ray nature of the incident flux. Detailed differential energy spectra were obtained with the IMP-6 for six of the eight known events occurring during the March 1971 to September 1972 lifetime of the instrument. All of these are multiple-pulse events, with several seconds separation between distinct pulses of one or two seconds duration. The pulse spectra do not obey single-index power laws in energy, but can be represented by exponentials in photon flux throughout the 100 to 1200 KeV region.
The Vela pulsar PSR 0833-45, located in the Vela X nebula, has the second shortest period of any of the known radio pulsars. Soft X-ray observations are described which place an upper limit of 0.3% on the pulsed fraction of the Vela pulsar relative to the flux from the entire Vela X Nebula, in the 0.5- to 1.0-keV energy band. The present results are about a factor of 7 below the value of 2% measured by Harnden and Gorenstein (1973) for the pulsed fraction relative to the flux from the Vela X Nebula.
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A triple peaked 1.24 sec. pulse profile in a 1-minute rocket borne exposure to Her X-1 was measured, in contrast to the doublepeaked profiles expected from models which maximize the X ray emission at the magnetic equator of an accreting neutron star. The profile exhibits statistically significant energy dependence, with the emission approximately greater than 12 keV having narrower peaks which lag (by approximately 5% of the pulse period) the corresponding peaks at lower energies. Approximately one third of the total emission from the source is nonpulsed.