Engineering topics

Lingenfelter, R. E.

Publications and source records attributed to Lingenfelter, R. E..

At least 37 records · Page 2

NASA NTRS1987

Calculated gamma-ray line fluxes from the Type II supernova 1987 A

Calculations of the time-dependent flux in the 847-keV gamma-ray line from the decay of Co-56 that might be expected from the type II supernova 1987 A in the LMC are presented. It is found that, for a wide range of assumed Co-56 and supernova ejecta masses, this line should be detectable by planned gamma-ray observations with flux sensitivities of about 0.0001 photons/sq cm sec. If this line is detected, the measurement of its time-dependent flux together with its width will make it possible to determine not only the mass of Co-56 produced by explosive nucleosynthesis, but also the total mass and energy of the ejecta, and hence the mass of the supernova's progenitor.

Chan, L. W.↗

NASA NTRS1987

Positrons from accelerated particle interactions

Positron production from the decay of radioactive nuclei produced in nuclear interactions of accelerated particles is treated in detail. Laboratory data as well as theoretical considerations are used to construct energy-dependent cross sections for the production of a large number of radioactive positron emitters resulting from proton and alpha-particle interactions with ambient cosmic matter. Using these cross sections, positron production rates are calculated for a variety of energetic particle spectra, assuming solar abundances for both the energetic particles and the ambient medium. These results can be used for the study of astrophysical sites which emit annihilation radiation. In particular, the results have been applied to solar flares, where the observed 0.511 MeV line is shown to be due to positrons resulting from accelerated particle reactions.

Kozlovsky, B.↗

NASA NTRS1986

Gamma-ray burst size-frequency distributions - Spectral and temporal selection effects

The effects of spectral variation on the detection of gamma ray bursts were investigated. Selection biases resulting from these effects can account for the reported deviation of the observed size-frequency distribution in peak energy flux from that expected for a simple uniform distribution of sources. Thus these observations as yet provide no clear evidence for structure in the burst source distribution. Because of selection biases, the intrinsic average temperature of the bursts is much harder (kT approximately MeV) than the observed average (approximately 200 keV).

Higdon, J. C.↗

NASA NTRS1986

Gamma-ray line astrophysics

Recent observations of gamma-ray line emission from solar flares, gamma-ray bursts, the galactic center, the interstellar medium and the jets of SS433 are reviewed. The implications of these observations on high energy processes in these sources are discussed.

Lingenfelter, R. E.↗

NASA NTRS1986

Topics in gamma ray astronomy

Observations of gamma rays from solar flares, gamma ray bursts, the Galactic center, galactic nucleosynthesis, SS433, and Cygnus X-3, and their effects on astrophysical problems are discussed. It is observed that gamma ray spectra from solar flares are applicable to the study of particle acceleration and confinement and the determination of chemical abundances in the solar atmosphere. The gamma ray lines from the compact galactic object SS433 are utilized to examine the acceleration of jets, and analysis of the gamma ray lines of Cygnus X-3 reveal that particles can be accelerated in compact sources to ultrahigh energies.

Ramaty, R.↗

NASA NTRS1986

Cosmic gamma-ray lines

Recent observations of gamma-ray line emissions from gamma-ray bursts, the ISM, the Galactic center, and solar flares are reviewed, and the implications of these observations for high-energy processes in these sources are discussed. Line observations suggest that magnetized neutron stars are probably the best candidate objects for burst sources. Observations of the 1.809-MeV line from Al-26 decay provide evidence for ongoing nucleosynthesis in the Galaxy and information on the spatial distribution of nucleosynthetic sites. The compact 0.511-MeV line source is probably a black hole at or close to the Galactic center. Solar-flare studies have provided new information on the confinement and escape of charged particles at the sun and on multiple acceleration phases in solar flares.

Ramaty, R.↗

NASA NTRS1985

Gamma ray burst size-frequency distributions: Spectral selection effects

Higdon, J. C.↗

NASA NTRS1985

Nuclear processes and neutrino production in solar flares

The determination of flare neutrino flux is approached from the standpoint of recent observations and theoretical results on the nuclear processes in solar flares. Attention is given to the energy spectra and total numbers of accelerated particles in flares, as well as their resulting production of beta(+)-emitting radionuclei and pions; these should be the primary sources of neutrinos. The observed 0.511 MeV line flux for the June 21, 1980 flare is compared with the expected from the number and spectrum of accelerated particles.

Lingenfelter, R. E.↗

NASA NTRS1984

A 164-day period in gamma-ray bursts from GBS0526-66?

Evidence is presented for a pattern in the recurrence time of gamma ray bursts from GBS0526-66, showing an apparent period of 164 days. It is suggested that this pattern reflects periodic accretion to a neutron star from an eccentric binary companion. It is proposed that this system drives two types of bursts: (1) the relatively frequent but weak recurrent bursts produced by either magnetospheric gating, or thermonuclear runaway, of periodically accreting matter around the neutron star, and (2) the much rarer intense bursts produced by tidally triggered star quakes.

Rothschild, R. E.↗

NASA NTRS1984

Nuclear processes in the jets of SS 433

The very narrow gamma-ray lines observed at 1.495 and 6.695 MeV from SS 433 which are blueshifted 1.369 and 6.129 emissions from deexcitations of (24)Mg-asterisk and (16)O-asterisk in grains moving with the jets and inelastically excited by interactions with the ambient medium are discussed. Energetic particle interactions in grains produce very narrow gamma ray lines from deexcitation of nuclear levels whose lifetimes are long enough that the excited nuclei stop before deexcitation. The presence of grains in the jets resolves hitherto discussed difficulties of inelastic excitation models for gamma ray production in SS 433, the very narrow widths of the observed lines and the absence of other strong lines, expected from abundant elements. A model is proposed which could be distinguished from a previously proposed fusion model by gamma ray line observations.

Ramaty, R.↗

NASA NTRS1984

Nuclear processes in the jets of SS433

The very narrow gamma-ray lines observed at 1.495 and 6.695 MeV from SS433 which are blueshifted 1.369 and 6.129 emissions from deexcitations of (24)Mg* and (16)O* in grains moving with the jets and inelastically excited by interactions with the ambient medium are discussed. Energetic particle interactions in grains produce very narrow gamma ray lines from deexcitation of nuclear levels whose lifetimes are long enough that the excited nuclei stop before deexcitation. The presence of grains in the jets resolves hitherto discussed difficulties of inelastic excitation models for gamma ray production in SS433, the very narrow widths of the observed lines and the absence of other strong lines, expected from abundant elements. A model is proposed which could be distinguished from a previously proposed fusion model by gamma ray line observations.

Ramaty, R.↗

NASA NTRS1983

Implications of high-energy neutron observations from solar flares

The time-dependent flux of high-energy neutrons discovered from the solar flare of 1980 June 21 provides a new technique for determining the total number and energy spectrum of accelerated protons and nuclei at the sun. The implications of these observations on gamma-ray emission, relativistic electron spectrum and number, proton and electron energy contents, and the location of the interaction region are also examined.

Ramaty, R.↗

NASA NTRS1983

Gamma-ray lines and neutrons from solar flares

The energy spectrum of accelerated protons and nuclei at the site of a limb flare was derived by a technique, using observations of the time dependent flux of high energy neutrons at the earth. This energy spectrum is very similar to the energy spectra of 7 disk flares for which the accelerated particle spectra was previously derived using observations of 4 to 7 MeV to 2.223 MeV fluence ratios. The implied spectra for all of these flares are too steep to produce any significant amount of radiation from pi meson decay. It is suggested that the observed 10 MeV gamma rays from the flare are bremsstrahlung of relativistic electrons. Previously announced in STAR as N83-19695

Ramaty, R.↗

NASA NTRS1983

The Origin of the Galactic Annihilation Radiation

Observations of the e(+)-e(-) annihilation radiation from the galactic center are reviewed and the implications of these and other observations on the positron production process, the annihilation region and the fundamental nature of the galactic center source are discussed.

Lingenfelter, R. E.↗

NASA NTRS1983

Gamma-ray lines and neutrons from solar flares

The energy spectrum of accelerated protons and nuclei at the site of a limb flare was derived by a technique, using observations of the time dependent flux of high energy neutrons at the Earth. This energy spectrum is very similar to the energy spectra of 7 disk flares for which the accelerated particle spectra was previously derived using observations of 4 to 7 MeV to 2.223 MeV fluence ratios. The implied spectra for all of these flares are too steep to produce any significant amount of radiation from pi meson decay. It is suggested that the observed 10 MeV gamma rays from the flare are bremsstrahlung of relativistic electrons.

Ramaty, R.↗

NASA NTRS1983

Advances in gamma-ray line astronomy

Gamma ray line observations of solar flares, gamma ray transients, and the galactic center are reviewed and interpreted. Prospects of future line detections are discussed. Previously announced in STAR as N82-27200

Ramaty, R.↗

NASA NTRS1983

Positron-electron annihilation radiation from the Galactic Center

Evidence and arguments are presented supporting the theory that the 0.511 MeV line observed from the Galactic Center stems from photon-photon pair production near a black hole with a mass not greater than approximately 500 solar masses. Observations are reviewed and the subsequent implications on the annihilation site and the positron source are discussed. Because of the variations and line width of the e(+) - e(-) annihilation radiation from the Galactic Center, positrons must essentially be produced by a single source and annihilate in an ambient gas of density greater than 10 to the 5th/cu cm, an ionization fraction greater than 10 percent, a temperature less than 5 x 10 to the 4th K, and be confined to a region of size less than 10 to the 18th cm. Such conditions may exist in warm clouds and other IR sources within the central parsec of the Galaxy.

Ramaty, R.↗

NASA NTRS1983

A distance model for gamma-ray bursts

The apparent contradiction between the isotropic latitude distribution and the flat size-frequency distribution of gamma-ray bursts is discussed. It is shown that the data are not inconsistent but rather can be easily explained by a nonsingular distribution of burst energies such as that implied by a fireball model for gamma-ray bursts.

Lingenfelter, R. E.↗