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Annihilation Radiation

The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform

W R Purcell – 1st expert on this subject based on the ideXlab platform

  • The distribution of galactic 511 keV positron Annihilation Radiation
    AIP Conference Proceedings, 2008
    Co-Authors: W R Purcell, J D Kurfess, R L Kinzer, M S Strickman, W N Johnson, D A Grabelsky, M P Ulmer, G V Jung

    Abstract:

    The Oriental Scintillation Spectrometer Experiment (OSSE) on NASA’s Compton Gamma‐Ray Observatory has completed numerous observations of the Galactic plane and Galactic center region. A principle objective of these observations was to measure the distribution of the Galactic positron Annihilation Radiation. Most of these observations provided positive detections of the narrow 511 keV Annihilation line. These data were fitted using several diffuse distribution models representing various populations of progenitor objects. The only model investigated which is not rejected is a two‐component distribution consisting of spheroidal and disk components; all other models investigated can be rejected at the ≳4.5σ confidence level. The size of the spheroidal component is found to be

  • positron Annihilation Radiation from the inner galaxy
    The Astrophysical Journal, 2001
    Co-Authors: R L Kinzer, P A Milne, J D Kurfess, M S Strickman, W N Johnson, W R Purcell

    Abstract:

    The OSSE instrument on the Compton Gamma Ray Observatory (CGRO) was used to measure the one-dimensional latitudinal and longitudinal distributions of positron Annihilation Radiation (Annihilation line and positronium continuum components) along the inner Galactic ridge. Intensity measurements near the Galactic center (differential relative to background fields offset by 9°-12°) show a symmetrical and spatially narrow bulge around the center (effective FWHMs of 49 ± 07 in Galactic latitude and 63 ± 15 in longitude) with significant disk contributions to at least 35° in longitude. The latitude width of the Galactic plane emission away from the Galactic center is only weakly constrained in the current analysis. The longitudinal distribution is well fitted by either a model comprising a narrow (~63 FWHM ) Gaussian bulge plus ~35° FWHM Gaussian and CO-like disk components, or by a center-truncated R1/4 spheroid plus exponential disk model. For the latter model, the observed narrow latitudinal distribution near the Galactic center suggests that the bulge is ellipsoidal, although the fits are consistent with a spherical bulge as well. The positronium fraction estimate from the Galactic center direction is 0.93 ± 0.04. This, combined with the existing narrow line width measurements for the 511 keV Annihilation line, suggests that the bulk of the positron Annihilation from the Galactic center direction occurs after positronium formation in a warm environment. The inner Galaxy total Annihilation Radiation flux intensities of ~10.6 × 10-3 to ~13.7 × 10-3 cm-2 s-1 implied by the fitted R1/4 ellipsoid plus exponential disk model (narrow and broad disks, respectively) are in agreement with intensities implied by the 511 keV line flux observed by the broad-field SMM instrument. The double-Gaussian plus CO disk model gives similar agreement if a broad (~12° FWHM) disk component is assumed.

  • OSSE observations of galactic 511 keV Annihilation Radiation
    , 1993
    Co-Authors: W R Purcell, R L Kinzer, M S Strickman, W N Johnson, D A Grabelsky, M P Ulmer, J D Kurfess, G V Jung

    Abstract:

    The Oriented Scintillation spectrometer Experiment (OSSE) on the Compton Gamma‐Ray Observatory has performed numerous observations of the galactic plane and galactic center region to measure the distribution of galactic 511 keV positron Annihilation Radiation and to search for time variability of the emission. These observations show conclusive evidence for a narrow 511 keV line and positronium continuum. For the first OSSE galactic center observation, the fitted 511 keV line flux was (2.3±0.3)×10−4 γ cm−2 s−1 and the positronium continuum flux was (8.8±0.7)×10−4 γ cm−2 s−1, corresponding to a positronium fraction (0.96±0.04). The quoted uncertainty in the positronium flux does not include the effect of the underlying continuum model on the fitted positronium flux. No significant time variability of the line flux has been observed; the 3σ upper limit to daily variations from the mean is 3×10−4 γ cm−2 s−1. The galactic distribution of the 511 keV line emission is found to be most consistent with a 2‐compon…

R L Kinzer – 2nd expert on this subject based on the ideXlab platform

  • Supernovae and positron Annihilation Radiation
    New Astronomy Reviews, 2020
    Co-Authors: P A Milne, J D Kurfess, R L Kinzer, M D Leising

    Abstract:

    Radioactive nuclei, especially those created in SN explosion, have long been
    suggested to be important contributors of galactic positrons. In this paper we
    describe the findings of three independent OSSE/SMM/TGRS studies of positron
    Annihilation Radiation, demonstrating that the three studies are largely in
    agreement as to the distribution of galactic Annihilation Radiation. We then
    assess the predicted yields and distributions of SN-synthesized radionuclei,
    determining that they are marginally compatible with the findings of the
    Annihilation Radiation studies.Comment: 7 pages, accepted for publication in New Astronomy Reviews (Astronomy
    with Radioactivites III

  • The distribution of galactic 511 keV positron Annihilation Radiation
    AIP Conference Proceedings, 2008
    Co-Authors: W R Purcell, J D Kurfess, R L Kinzer, M S Strickman, W N Johnson, D A Grabelsky, M P Ulmer, G V Jung

    Abstract:

    The Oriental Scintillation Spectrometer Experiment (OSSE) on NASA’s Compton Gamma‐Ray Observatory has completed numerous observations of the Galactic plane and Galactic center region. A principle objective of these observations was to measure the distribution of the Galactic positron Annihilation Radiation. Most of these observations provided positive detections of the narrow 511 keV Annihilation line. These data were fitted using several diffuse distribution models representing various populations of progenitor objects. The only model investigated which is not rejected is a two‐component distribution consisting of spheroidal and disk components; all other models investigated can be rejected at the ≳4.5σ confidence level. The size of the spheroidal component is found to be

  • supernovae and positron Annihilation Radiation
    New Astronomy Reviews, 2002
    Co-Authors: P A Milne, J D Kurfess, R L Kinzer, M D Leising

    Abstract:

    Radioactive nuclei, especially those created in SN explosion, have long been suggested to be important contributors of galactic positrons. In this paper we describe the findings of three independent OSSE/SMM/TGRS studies of positron Annihilation Radiation, demonstrating that the three studies are largely in agreement as to the distribution of galactic Annihilation Radiation. We then assess the predicted yields and distributions of SN-synthesized radionuclei, determining that they are marginally compatible with the findings of the Annihilation Radiation studies.

P. Von Ballmoos – 3rd expert on this subject based on the ideXlab platform

  • INTEGRAL/IBIS search for e – e + Annihilation Radiation from the galactic center region
    Advances in Space Research, 2020
    Co-Authors: G De Cesare, V. Lonjou, F Capitanio, M Del Santo, L Natalucci, P Ubertini, Angela Bazzano, P. Von Ballmoos

    Abstract:

    Abstract Electron–positron Annihilation Radiation from the Galactic Center Region has been detected since the seventies, but its astrophysical origin is still a topic of a scientific debate. We have analyzed data of the gamma-ray imager IBIS/ISGRI onboard of ESA’s INTEGRAL platform in the e − e + line. During the first year of the missions Galactic Center Deep Exposure no evidence for point sources at 511 keV has been found in the ISGRI data; the 2 σ upper limit for resolved single point sources is estimated to be 1.6 × 10 −4 ph cm −2  s −1 .

  • integral ibis search for e e Annihilation Radiation from the galactic center region
    Advances in Space Research, 2006
    Co-Authors: G De Cesare, V. Lonjou, A Bazzano, F Capitanio, M Del Santo, L Natalucci, P Ubertini, P. Von Ballmoos

    Abstract:

    Abstract Electron–positron Annihilation Radiation from the Galactic Center Region has been detected since the seventies, but its astrophysical origin is still a topic of a scientific debate. We have analyzed data of the gamma-ray imager IBIS/ISGRI onboard of ESA’s INTEGRAL platform in the e − e + line. During the first year of the missions Galactic Center Deep Exposure no evidence for point sources at 511 keV has been found in the ISGRI data; the 2 σ upper limit for resolved single point sources is estimated to be 1.6 × 10 −4 ph cm −2  s −1 .

  • integral spi limits on electron positron Annihilation Radiation from the galactic plane
    The Astrophysical Journal, 2005
    Co-Authors: Bonnard J. Teegarden, V. Lonjou, G. Weidenspointner, J. Knödlseder, P. Jean, P. Von Ballmoos, J. P. Roques, K Watanabe, G Skinner, A Bazzano

    Abstract:

    The center of our Galaxy is a known strong source of electron-positron 511 keV Annihilation Radiation. Thus far, however, there have been no reliable detections of Annihilation Radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched in 2002 October, is the detailed study of this Radiation. The Spectrometer on INTEGRAL (SPI) is a high-resolution, coded-aperture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution, and energy resolution. We report results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic plane. No positive Annihilation flux was detected outside of the central region ( l > 40°) of our Galaxy. In this paper we describe the observations and data analysis methods and give limits on the 511 keV flux.