HEAO-1 observations of HER X-1 at energies above 13 keV in February 1978
Explore the source record for details and available documents.
Matteson, J. L.↗
Engineering topics
Gruber, D. E.
Publications and source records attributed to Gruber, D. E..
HEAO observations of X-ray bursts from MXB1730-335
The March 18, 1978 burst activity of the rapid burster MXB 1730-335 was studied by examining 58 minutes of quick-look data for the A2 and A4 experiments on HEAO 1. Very large, moderately sized, and small bursts are characterized. Type II bursts were found to show a spectral softening during burst decay. The existence of flux was sought in the 85-160 keV energy range, and it was found that the large type II bursts contain less than 5% of their total X-ray energy in this range. The implications of the lack of a hard X-ray flux with respect to accretion instability models of X-ray bursts are considered.
Hoffman, J. A.↗
HEAO-1 observations of Her X-1 at energies above 13 keV
Results from preliminary analysis of HEAO-1 pointing observations of Her X-1 on three days in February 1978 are presented. Pulsed flux is detected up to approximately 70 keV with a clear indication of emission at approximately 60 deV which is above the continuum spectrum extrapolated from lower energies. If this excess emission is interpreted as a spectral line, its intensity varies from (1.2 plus or minus 0.2) x (10 to the minus 3 power) to (0.2 plus or minus 0.2) x (10 to the minus 3 power) ph/sq cm-sec with a time scale of one day. A factor 2 decrease in the low energy continuum is associated with the decrease in the excess emission.
Matteson, J. L.↗
Evidence for detection of 1-10 MeV emission from the Taurus region in 1971 August
Results are reported for three observations of the Crab Nebula with a balloon-borne actively collimated NaI detector over the energy range from 0.2 to 10 MeV. Possible changes in instrument performance and environmental background levels during the balloon flights are investigated, and fits for source strength are made over four broad energy channels. X-ray power-law spectra and pulsed-flux fractions are determined for both the Crab Nebula and its pulsar, NP 0532. A statistically significant flux greatly in excess of the power law was detected above 1 MeV during one flight; this flux, which has declined by at least a factor of 4 or 5 at the times of more recent observations, is assumed to be real and is attributed to the nebula.
Gruber, D. E.↗
Spectra and angular distributions of atmospheric gamma rays from 0.3 to 10 MeV at lambda = 40 deg
Measurements of the spectral and angular distributions of atmospheric gamma sq cm rays in the energy range 0.3-10 MeV over Palestine, Texas, at residual depths of 2.5 and 70 g/sq cm are reported. In confirmation of the general features of a model prediction, the measurements show at 2.5 g/sq cm upward moving fluxes greater than the downward moving fluxes, the effect increasing with energy, and approximate isotropy at 70 g/sq cm. Numerous characteristic gamma-ray lines were observed, most prominently at 0.511, 1.6, 2.3, 4.4, and 6.1 MeV. Their intensities were also compared with model predictions. Observations were made with an actively shielded scintillator counter with two detectors, one of aperture 50 deg FWHM and the other of 120 deg FWHM. Above 1 MeV, contributions to the counting rate from photons penetrating the shield annulus and from neutron interactions were large; they were studied by means of a Monte Carlo code and are extensively discussed.
Ling, J. C.↗
Crab Nebula observations - 0.2-10 MeV
Observations of the total emission from the Crab Nebula and also of the pulsed component were made over the 0.2 to 10-MeV range during three balloon flights in 1971 with an actively-collimated NaI scintillator. The total emission flux was positively observed over the entire interval. The observed spectrum to 1 MeV agrees with an extrapolation of the E to the -2.2 power law, which fits lower-energy data. The observations above 1 MeV are factors of 3 and 20 above this law and are better fit with a spectral index of 0.8. Confidence levels are 3 sigma or better for each half-decade band. The three observations are consistent with a constant flux level. The NP 0532 flux, detected during one flight only (August 8) between 0.2 and 0.38 MeV, agrees with the exponential power law spectrum already determined from other observations. The possibility of a rapidly rising pulsed emission fraction over the 0.1- to 1-MeV interval is excluded by this observation.
Gruber, D. E.↗
Observation of MeV gamma-ray events during May 1967 from ERS-18
Gamma-ray fluxes between 25 keV and 6 MeV were observed by instruments aboard the Environmental Research Satellite-18 (ERS-18)during the great solar flares of May 21 and May 23, 1967. Measurements were made with a 6.35-cm-diameter by 7.65-cm-long Nal scintillation counter with five differential channels between 0.25 and 6.0 MeV. Data obtained during the event at 1945 UT on May 23, 1967, can be fitted by a two-part, power-law, differential-number spectrum. One part is of spectral index 3.2 between 8 keV and 0.6 MeV, and the other is of spectral index 1.2 above 0.6 MeV. An upper limit of 0.52 photons is set for 2.23 MeV line strength for this event. In all three bursts, tentatively associated with white light flares, the MeV-range fluxes declined more slowly than the 25-keV fluxes.
Gruber, D. E.↗