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Haymes, R. C.

Publications and source records attributed to Haymes, R. C..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Evidence for variability of the hard X-ray feature in the Hercules X-1 energy spectrum

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 the data with the results of the MPI/AIT group shows statistically significant variations which strongly suggest variability in the source. Previously announced in STAR as N83-37036

Tueller, J.↗
NASA NTRS1983

Evidence for variability of the hard X-ray feature in the Hercules X-1 energy spectrum

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.

Tueller, J.↗
NASA NTRS1980

The hard X-ray periodicity of GX 1 + 4

Pulses that recur with a 4.27 + or - 0.01 minute period were detected on April 2, 1974 in the 20-64 keV X-radiation from the galactic center region. Apparently emanating from GX 1 + 4, a major contributor to the high-energy radiation from that region, the pulses were 1.25 + or - 0.42 minutes in duration. If it is in fact the same source that has been observed on all occasions, the period is twice that previously believed.

Koo, J.-W. C.↗
NASA NTRS1979

Observations of Cygnus X-3 above 50 keV

Cygnus X-3 was observed in the energy range 50-400 keV using a balloon-borne, actively collimated, NaI(Tl) scintillation detector. The observation was made from phase 0.45-0.91 of the 4.8 hour period. The photon number spectrum was well represented by a power law with index -2.2. The flux increased throughout the observation, consistent with a highly asymmetric light curve with a peak near phase 0.9.

Meegan, C. A.↗
NASA NTRS1979

Evidence for variability of hard X-rays from NGC 4151

A search for gamma-rays in the 35-keV to 8.7-MeV energy range from the Seyfert galaxy NGC 4151 was made using an actively collimated scintillation detector. Upper limits to the flux in the 100-200-keV energy range are inconsistent with previous observations. Variability on a time scale of several months is indicated. Implications in terms of current models of NGC 4151 are discussed.

Meegan, C. A.↗
NASA NTRS1979

A search for low energy gamma rays from CG 195+4

A 13-deg-wide region of sky containing the high-energy gamma-ray source CG 195+4 was searched for X-ray and gamma-ray emission in the energy interval from 0.035 to 8.737 MeV. The balloon-altitude measurements were undertaken on October 4, 1977, at Palestine, Texas, and used an actively collimated scintillation counter. As a result of the measurements, low upper limits have been found for the spectrum from the source. Combined with the positive detections made with satellites at high energies, the measurements show that the photon number spectrum must have a spectral index harder than 2.0. The data appear inconsistent with models of the source in which the presumed neutron star is surrounded by a cloud thick to X-rays. Negative results of the search for periodicity are discussed.

Haymes, R. C.↗
NASA NTRS1978

Future directions in experimental gamma ray astronomy

Better vehicles and instruments are needed if gamma ray spectroscopy in astrophysics and cosmology is to advance. A gamma ray observatory will (1) permit long-term observations of selected sources to measure their variability and to achieve high sensitivity; (2) measure periods in days or weeks; and (3) assess the entire sky to observe various predicted sources, to measure the energy spectrum, and to map the isotropy of the cosmic ray background over larger collecting areas (of the order of a square meter). Conventional and unconventional instruments must cover the energy range from 0.1 MeV to 20 MeV with improved sensitivity. Angular resolution must be improved one degree or more to study discrete X-ray sources in the galactic center. Actively collimated detectors, improved double Compton instruments, and gamma ray correlators to actively synthesize the absolute energy spectrum of the sky protons are discussed as well as the need for scientific balloons.

Haymes, R. C.↗
NASA NTRS1976

Detection of nuclear gamma rays from Centaurus A

Results are reported for an observation of nuclear gamma rays in the energy range between 0.033 and 12.25 MeV from Centaurus A using a balloon-borne actively collimated NaI(Tl) crystal scintillation counter. The observing procedure is outlined, no systematic errors are found in the data, and power-law fits to the source's energy spectrum are attempted. A power law of approximately 0.86E to the -1.9 power photon/sq cm/sec per keV is shown to give an acceptable fit to the continuum, and the detection of two gamma-ray lines at 1.6 and 4.5 MeV, respectively, is discussed. It is found that the low-energy gamma-ray luminosity of Cen A is 9.4 by 10 to the 43rd power erg/sec for a distance of 5 Mpc and that Cen A is apparently variable in low-energy gamma radiation. It is suggested that the broad feature detected at 1.6 MeV may be due to three blended lines (possibly excited Ne-20, Mg-24, and Si-28), the 4.5-MeV line is most likely due to deexcitation of excited C-12, and the nuclear excitation results from either cosmic-ray bombardment of Cen A's interstellar medium or nucleosynthesis within the source.

Hall, R. D.↗
NASA NTRS1976

Radioactivity in the galactic plane

The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

Walraven, G. D.↗