OSSE Mapping of Galactic 511 keV Positron Annihilation Line Emission

Purcell, W. R.; Liu, Cheng; Dixon, David; Kinzer, R. L.; Kurfess, J. D.; Leventhal, M.; Saunders, MA; Skibo, J. G.; Smith, David M.; Tueller, J.

doi:10.1086/304994

Cited by 138 publications

(177 citation statements)

References 51 publications

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“…The scientific surprise of this emission had already been apparent in earlier results from the Compton Observatory [103], and was consolidated by SPI measurements: The annihilation emission predominantly arises in the inner Galaxy in an extended region of size 10 • . By comparison, the disk of the Galaxy is much fainter, wit a bulge-to-disk intensity ratio of 1.4 from a total luminosity of 2 10 −3 ph cm −2 s −1 [70,144].…”

Section: Positron Annihilationmentioning

confidence: 78%

Cosmic Gamma-Ray Spectroscopy

Diehl

2013

Astronomical Review

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Penetrating gamma-rays require complex instrumentation for astronomical spectroscopy measurements of gamma-rays from cosmic sources. Multiple-interaction detectors in space combined with sophisticated postprocessing of detector events on ground have lead to a spectroscopy performance which is now capable to provide new astrophysical insights. Spectral signatures in the MeV regime originate from transitions in the nuclei of atoms (rather than in their electron shell). Nuclear transitions are stimulated by either radioactive decays or high-energy nuclear collisions such as with cosmic rays. Gamma-ray lines have been detected from radioactive isotopes produced in nuclear burning inside stars and supernovae, and from energetic-particle interactions in solar flares. Radioactive-decay gamma-rays from 56 Ni directly reflect the source of supernova light. 44 Ti is produced in core-collapse supernova interiors, and the paucity of corresponding 44 Ti gamma-ray line sources reflects the variety of dynamical conditions herein. 26 Al and 60 Fe are dispersed in interstellar space from massive-star nucleosynthesis over millions of years. Gamma-rays from their decay are measured in detail by gamma-ray telescopes, astrophysical interpretations reach from massive-star interiors to dynamical processes in the interstellar medium. Nuclear de-excitation gamma-ray lines have been found in solar-flare events, and convey information about energetic-particle production in these events, and their interaction in the solar atmosphere. The annihilation of positrons leads to another type of cosmic gamma-ray source. The characteristic annihilation gamma-rays at 511 keV have been measured long ago in solar flares, and now throughout the interstellar medium of our Milky Way galaxy. But now a puzzle has appeared, as a surprising predominance of the central bulge region was determined. This requires either new positron sources or transport processes not yet known to us. In this paper we discuss instrumentation and data processing for cosmic gamma-ray spectroscopy, and the astrophysical issues and insights from these measurements.

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Section: Positron Annihilationmentioning

confidence: 78%

Cosmic Gamma-Ray Spectroscopy

Diehl

2013

Astronomical Review

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show abstract

Section: Positron Annihilationmentioning

confidence: 79%

Cosmic Gamma-Ray Spectroscopy

Diehl¹

2013

Astronomical Review

View full text Add to dashboard Cite

Penetrating gamma-rays require complex instrumentation for astronomical spectroscopy measurements of gamma-rays from cosmic sources. Multiple-interaction detectors in space combined with sophisticated postprocessing of detector events on ground have lead to a spectroscopy performance which is now capable to provide new astrophysical insights. Spectral signatures in the MeV regime originate from transitions in the nuclei of atoms (rather than in their electron shell). Nuclear transitions are stimulated by either radioactive decays or high-energy nuclear collisions such as with cosmic rays. Gamma-ray lines have been detected from radioactive isotopes produced in nuclear burning inside stars and supernovae, and from energetic-particle interactions in solar flares. Radioactive-decay gamma-rays from 56 Ni directly reflect the source of supernova light. 44 Ti is produced in core-collapse supernova interiors, and the paucity of corresponding 44 Ti gamma-ray line sources reflects the variety of dynamical conditions herein.26 Al and 60 Fe are dispersed in interstellar space from massive-star nucleosynthesis over millions of years. Gamma-rays from their decay are measured in detail by gamma-ray telescopes, astrophysical interpretations reach from massive-star interiors to dynamical processes in the interstellar medium. Nuclear de-excitation gamma-ray lines have been found in solar-flare events, and convey information about energetic-particle production in these events, and their interaction in the solar atmosphere. The annihilation of positrons leads to another type of cosmic gamma-ray source. The characteristic annihilation gamma-rays at 511 keV have been measured long ago in solar flares, and now throughout the interstellar medium of our Milky Way galaxy. But now a puzzle has appeared, as a surprising predominance of the central bulge region was determined. This requires either new positron sources or transport processes not yet known to us. In this paper we discuss instrumentation and data processing for cosmic gamma-ray spectroscopy, and the astrophysical issues and insights from these measurements.

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“…Possibly 0.511 MeV e + e − -annihilation line line from the galactic center and maybe even from the galactic halo [37,38] are the first positive indications to cosmological antimatter.…”

Section: Resultsmentioning

confidence: 99%