Engineering topics

Barthelmy, S. D.

Publications and source records attributed to Barthelmy, S. D..

41 records · Page 3

NASA NTRS1991

GRIS observations of positron annihilation radiation from the Galactic center

In the present Gamma-Ray Imaging Spectrometer (GRIS) observations, the 511 keV line has been spectrally resolved and the Galactic plane and center components have been independently measured. These data, in combination with those from other narrow-field observations in the 1980s, support the two-component model of the positron annihilation source. A strong hard-X-ray continuum was detected in the Galactic plane observation; this 'diffuse' continuum component solves the mystery as to why wide-field instruments have detected such high continuum emission from the Galactic center, in virtue of its source contributions.

Gehrels, N.↗

NASA NTRS1989

Resolution of the 1,238-keV gamma-ray line from supernova 1987A

Observations of supernova 1987A from the maiden flight of the Gamma-Ray Imaging Spectrometer (GRIS) are reported. SN1987A was observed for a period of 11.1 hours on May 1, 1988. Line emission at 1238 keV and continuum emission from 60-800 keV were detected. A gaussian line profile gives an acceptable fit to the 1238 keV line. The best-fit parameters are: flux = 8.5(+ 2.3, - 2.2) x 10 to the -4th photons/sq cm/s; peak energy = 1235.4 (+ 2.2, - 2.4) keV; FWHM = 16.3 (+ 6.1, - 5.7) keV. No evidence is found for a supernova-produced red- or blueshift in the 1238 keV line. The measured linewidth is a factor of about two greater than model predictions, although the discrepancy represents only two standard deviations. The line profiles are characteristic of optically thin regions, whereas the intensity implies a mean optical depth of about two. Fragmentation or nonspherical geometry of the supernova shell are possible explanations of the data.

Teegarden, B. J.↗

NASA NTRS1989

Reappearance of the annihilation line source at the Galactic Centre

The results of a new balloon-borne measurements of gamma-ray emission from the Galactic Center using a germanium telescope are reported. The 511-keV line was detected at a flux level of (9.8 + or - 1.9) x 10 to the -4th photons/sq cm/s on May 1, 1988 and (12.3 + or - 1.6) x 10 to the -4th photons/sq cm/s on October 29, 1988. Apparently the compact object reemerged sometime between 1984 and 1988. Flux was also measured from a point in the Galactic Plane 25 deg west of the Galactic Center, and was found to be (2.4 + or - 1.7) x 10 to the -4th photons/sq cm/s.

Leventhal, M.↗

NASA NTRS1985

Relative abundances of elements (20 or = Z or = 28) at energies up to 70 GeV/amu using relativistic rise in ion chambers

The results of a new balloon borne cosmic ray detector flown from Palestine, TX in Sept., 1982 are discussed. The exposure of 62 square meter-ster-hr is sufficient to prove the concept of using gas ionization chambers as energy measuring devices in the relativistic rise region. The abundances, relative Fe-26, of the pure secondaries Cr-22 and Ti-24, the pure primary Ni26, and the mixed primary and secondary Ca-20 between 6 and 70GeV/amu were measured.

Barthelmy, S. D.↗

NASA NTRS1983

Use of relativistic rise in ionization chambers for measurement of high energy heavy nuclei

A balloon-borne instrument has been constructed to measure the energy spectra of cosmic-ray heavy nuclei in the range of about 0.3 to about 100 GeV/amu. It makes use of the relativistic rise portion of the Bethe-Bloch curve in ionization chambers for energy determination in the 10- to 100-GeV/amu interval. The instrument consists of six layers of dual-gap ionization chambers for energy determination above 10 GeV/amu. Charge is determined with a NE114 scintillator and a Pilot 425 plastic Cerenkov counter. A CO2 gas Cerenkov detector (1 atm; threshold of 30 GeV/amu) calibrates the ion chambers in the relativistic rise region. The main emphasis of the instrument is the determination of the change of the ratio of Iron (26) to the Iron secondaries (21-25) in the energy range of 10 to 100 GeV/amu. Preliminary data from a balloon flight in the fall of 1982 from Palestine, TX is presented.

Barthelmy, S. D.↗