Astrophysical Gamma Ray Emission Lines

Ramaty, R.; Lingenfelter, R. E.

doi:10.1017/cbo9780511600180.014

Cited by 6 publications

(7 citation statements)

References 39 publications

(102 reference statements)

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“…The Ϫ4 0.7 # 10 main surprise of this measurement is the width of the astrophysical line profile, which was significantly broader than the instrumental resolution of the germanium detector, and reported as keV. This line width is much larger than DE ϭ 5.4 ‫ע‬ 1.4 expected from Galactic rotation (≤1 keV; Gehrels & Chen 1996), which dominates above the broadening from random motions in the interstellar medium (Ramaty & Lingenfelter 1977. It is presently difficult to understand how such high-velocity motion could be maintained over the million year timescale of 26 Al decay.…”

Section: Al In the Galaxymentioning

confidence: 72%

“…The High-Energy Astronomical Observatory C (HEAO C) discovery of the 1.809 MeV g-ray line from radioactive 26 Al in the Galaxy (Mahoney et al 1982), which had been anticipated from theoretical considerations (Clayton 1971(Clayton , 1982Arnett 1977;Ramaty & Lingenfelter 1977;Lingenfelter & Ramaty 1978), opened new doors in g-ray astronomy. Measurements of various radioactive decays in the Milky Way offer a global proof of the idea that heavy-element formation is an ongoing process and is still happening inside stars (Burbidge et al 1957;Cameron 1957).…”

Section: Integrated Nucleosynthesismentioning

confidence: 99%

“…In the following review, attention is chiefly focused on the Milky Way's g-ray line emission that originates from the radioactive isotopes 7 Be, 22 Na, 26 Al, 44 Ti, 56 Ni, 57 Ni, and 60 Fe. The reviews by Lingenfelter & Ramaty (1978) and Ramaty & Lingenfelter (1995) provide excellent supplementary material.…”

Section: Introductionmentioning

confidence: 99%

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Gamma‐Ray Line Emission from Radioactive Isotopes in Stars and Galaxies

Diehl¹,

Timmes²

1998

PUBL ASTRON SOC PAC

110

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Our modern laboratory of nuclear physics has expanded to encompass parts of the universe, or at least our Galaxy. Gamma rays emitted by the decays of radioactive nuclei testify to the production of isotopes through nuclear processes in astrophysical events. We collect measurements of the Galactic g-ray sky in spectral lines attributed to the decay of radioactive 7 Be, 22 Na, 26 Al, 44 Ti, 56 Ni, 57 Ni, and 60 Fe. We organize and collate these measurements with models for the production sites in novae, supernovae, stellar interiors, and interstellar cosmic-ray interactions. We discuss the physical processes and the spatial distribution of these production sites, along with models of the chemical evolution of the Galaxy. Highlights of measurements made in the last decade include detailed images of the Galaxy in 26 Al radioactivity and detection of 56 Co and 57 Co from SN 1987A, 44 Ti from Cas A, and possibly 56 Ni from SN 1991T. The 26 Al mapping of recent Galactic nucleosynthesis may be considered as a new view on the entire ensemble of massive stars in the Galaxy. The local Cygnus region shows prominent radioactive emission from well-known stellar clusters, but the absence of g-rays from the closest Wolf-Rayet star, WR 11, in the Vela region is puzzling. SN 1987A studies in g-rays measure the radioactive powering of the supernova light curve directly, which will be particularly important for the dim late phase powered by 44 Ti. The 57 Ni/ 56 Ni isotopic ratio determinations from g-rays provide additional guidance for understanding SN 1987A's complex light curve and now appear to be uniformly settling to about twice the solar ratio. Cas A 44 Ti production as measured through g-rays presents the interesting puzzle of hiding the expected, coproduced, and large 56 Ni radioactivity. Core-collapse supernova models need to parameterize the inner boundary conditions of the supernova in one way or another, and now enjoy another measurement of the ejecta that is definitely originating from very close to the difficult regime of the mass cut between ejecta and compact remnant. Other relevant measurements of cosmic element abundances, such as observations of atomic lines from the outer shells of the production sites or meteoritic analysis of interstellar grains, complement the rather direct measurements of penetrating g-rays, thus enhancing the observational constraints of nuclear astrophysics models.

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Section: Al In the Galaxymentioning

confidence: 72%

Section: Integrated Nucleosynthesismentioning

confidence: 99%

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Gamma‐Ray Line Emission from Radioactive Isotopes in Stars and Galaxies

Diehl¹,

Timmes²

1998

PUBL ASTRON SOC PAC

110

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“…Note that inverse reactions between energetic heavy nuclei and ambient H and He yield de-excitation lines of width~1 MeV. This emission, together with many closely spaced and weak narrow lines, constitute broad unresolved features in the gamma Ramaty and Lingenfelter 1995) from the ion and electron spectra with the same spectral index. The dotted line is bremsstrahlung from the electrons, and the solid line is the total gamma ray emission.…”

Section: Theoretical Spectrummentioning

confidence: 97%

“…6.5 (Ramaty and Lingenfelter 1995). This spectrum has been calculated using the nuclear code of Ramaty et al (1979) with some recent updates (see also , under the assumption that the ion and electron spectra incident on a thick-target emission region are power laws of the same spectral index.…”

Section: Theoretical Spectrummentioning

confidence: 99%