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Positron Annihilation in the Galaxy with Next-Generation Gamma-ray Telescopes
Kierans, C.; Beacom, J.; Boggs, S. et al.
2020In Bulletin of the American Astronomical Society, Vol. 52
 

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Keywords :
Gamma-rays; Astrophysics; Space
Abstract :
[en] The 511 keV line from positron annihilation in the Galaxy was the first gamma-ray line detected to originate from outside our solar system. Going into the fifth decade since the discovery, the source of positrons is still unconfirmed and remains one of the enduring mysteries in gamma-ray astronomy. With a large flux of ~10[SUP]-3[/SUP] ph/cm[SUP]2[/SUP]/s, after 15 years in operation INTEGRAL/SPI has detected the 511 keV line at >50σ and has performed high-resolution spectral studies which conclude that Galactic positrons predominantly annihilate at low energies in warm phases of the interstellar medium. The results from imaging are less certain, but show a spatial distribution with a strong concentration in the center of the Galaxy. The observed emission from the Galactic disk has low surface brightness and the scale height is poorly constrained, therefore, the shear number of annihilating positrons in our Galaxy is still not well know. Positrons produced in β[SUP]+[/SUP] decay of nucleosynthesis products, such as [SUP]26[/SUP]Al, can account for some of the annihilation emission in the disk, but the observed spatial distribution, in particular the excess in the Galactic bulge, remains difficult to explain. Additionally, one of the largest uncertainties in these studies is the unknown distance that positrons propagate before annihilation. In this presentation, we will summarize the current knowledge base of Galactic positrons, and discuss how next-generation instruments such as AMEGO and COSI could finally provide the answers.
Research center :
STAR - Space sciences, Technologies and Astrophysics Research - ULiège
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Kierans, C.;  NASA/GSFC, Greenbelt, MD
Beacom, J.;  Australian National University, Canberra, Australia
Boggs, S.;  University of Liège, Liège, Belgium
Buckley, M.;  Institut de Recherche en Astrophysique et Planetologie, Toulouse, France
Caputo, R.;  Laboratoire Univers et particules de Montpellier, Montpellier, France
Crocker, R.;  Institut de Recherche en Astrophysique et Planetologie, Toulouse, France
De Becker, Michaël  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Diehl, R.;  Institut d'Astrophysique de Paris, Paris, France
Fryer, C.;  Max Planck Institute for extraterrestrial Physics, Garching, Germany)
Griffin, S.
Hartmann, D.
Hays, E.
Jean, P.
Krause, M.
Linden, T.
Marcowith, A.
Martin, P.
Moiseev, A.
Oberlack, U.
Panther, F.
Prantzos, N.
Rothschild, R.
Seitenzahl, I.
Shrader, C.
Siegert, T.
Strong, A.
Tomsick, J.
Vestrand, W.
Zoglauer, A.
More authors (19 more) Less
Language :
English
Title :
Positron Annihilation in the Galaxy with Next-Generation Gamma-ray Telescopes
Publication date :
01 January 2020
Event name :
American Astronomical Society meeting #235
Event date :
from 4-1-2020 to 8-1-2020
Audience :
International
Main work title :
Bulletin of the American Astronomical Society, Vol. 52
Pages :
372.22
Commentary :
235
Available on ORBi :
since 14 February 2021

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