Laurence E. Peterson

Lunar surface radioactivity - Preliminary results of the Apollo 15 and Apollo 16 gamma-ray spectrometer experiments.

Gamma-ray spectrometers on the Apollo 15 and Apollo 16 missions have been used to map the moons radioactivity over 20 percent of its surface. The highest levels of natural radioactivity are found in Mare Imbrium and Oceanus Procellarum with contrastingly lower enhancements in the eastern maria. The ratio of potassium to uranium is higher on the far side than on the near side, although it is everywhere lower than commonly found on the earth.

The hard solar X-ray spectrum observed from the third orbiting solar observatory.

Solar X-ray events observed by scintillation counter telescope on OSO 3 satellite, discussing X ray spectra during burst initial and decay phases

A scanning modulation collimator observation of the high-energy X-ray source in the Crab Nebula

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.

The cosmic gamma-ray spectrum between 0.3 and 27 MeV measured on Apollo 15.

The spectrum of the total (diffuse and discrete sources) cosmic gamma-ray background over the 0.3 to 27 MeV range was measured with a 7.0 cm diameter x 7.0 cm long uncollimated NaI(Tl) scintillation counter located on a boom 7.6 m from the Apollo 15 service module. Data on cosmic gamma-rays were taken during transearth coast at various boom extensions, detector gains, and with the plastic anticoincidence scintillator enabled and disabled.

HEAO 1 observations of gamma-ray lines from a solar flare

HEAO 1 observed gamma radiation, including the 2.223 MeV line of deuterium and the 4.43 MeV line of C-12, from a white-light solar flare of 1978 July 11. Line strengths over a 4 minute integration were 1.00 + or - 0.29 and 0.18 + or - 0.07 photons/sq cm s, respectively, and the continuum in the 1-5 MeV range fitted a spectrum 10 E to the -3rd photons/sq cm s keV. The 2.2 MeV line lagged 94 + or - 30 s behind the gamma-ray continuum, which itself was delayed about 20 s from the hard X-ray (not less than 40 keV) and microwave fluxes. This is the second flare for which both MeV-range lines and continuum have been observed, and the first for which simultaneous white-light observations exist. The prompt gamma-ray line (4.43 MeV) can be directly interpreted as an energy deposition of not greater than 7 x 10 to the 26th ergs per sec by energetic protons at photospheric depths. This is insufficient to maintain the white-light continuum by normal photospheric emission mechanisms.

Centaurus A /NGC 5128/ at 2 keV-2.3 MeV - HEAO 1 observations and implications

The nearby active-nucleus galaxy Centaurus A (NGC 5128) has been studied at 2 keV--2.3 MeV using data from both the UCSD/MIT hard X-ray and low energy ..gamma..-ray instrument and from the GSFC/CIT cosmic X-ray experiment on HEAO 1. We find that an E/sup -1.60plus-or-minus0.03/ power law spectrum breaking to E/sup -2.0plus-or-minus0.2/ at 140 keV best describes the 1978 January and July data. The average intensity was 50% higher during the January observations. We have searched our data for faster variations and set limits in several energy ranges over times from fractions of a day to several days. Upper limits to unresolved lines at 511 keV and 1.6 MeV are 6.5 x 10/sup -4/ photons cm/sup -2/ s/sup -1/ and 2.2 x 10/sup -4/ photons cm/sup -2/ s/sup -1/, respectively, at the 90% confidence level. Continuation of the observed power law to higher energies is used to constrain various models of energy generation in the nucleus of NGC 5128.

The Apollo gamma-ray spectrometer

Abstract A γ-ray spectrometer has been flown on the Apollo 15 and 16 spacecrafts to determine the lunar-surface composition and measure the cosmic γ- ay flux. The instrument included a Nal(Tl) scintillation crystal coupled to a 7.6 cm photomultiplier tube, a plastic mantle for anti-coincidence rejection of charged particles, and 511 channels of analysis. Boom-mounted operation permitted a significant reduction in the background. The data were transmitted on an event-by-event basis. About 22% of the lunar surface was mapped and spectra of the cosmic γ-ray flux over an energy range of 0.065–27.5 MeV have been obtained.

The x-ray spectrum of the plerionic system psr b1509-58/msh 15-52

We present the results of observations of the PSR B1509

Hercules X-1 hard X-ray pulsations observed from HEAO 1

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Observation of a cosmic gamma-ray burst on Apollo 16. I - Temporal variability and energy spectrum

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