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26 Al Radioactivity in the Galaxy

Published online by Cambridge University Press:  12 April 2016

R. Diehl ,
U. Oberlack ,
J. Knödlseder ,
K. Bennett ,
H. Bloemen ,
W. Hermsen ,
J. Ryan ,
V. Schönfelder  and
P. von Ballmoos
R. Diehl
Affiliation:
Max–Planck–Institut für extraterrestrische Physik, 85740 Garching, Germany
U. Oberlack
Affiliation:
Max–Planck–Institut für extraterrestrische Physik, 85740 Garching, Germany
J. Knödlseder
Affiliation:
Centre d’Etude Spatiale des Rayonnements, 31028 Toulouse Cedex, France
K. Bennett
Affiliation:
Astrophysics Division, ESTEC, ESA, 2200 AG Noordwijk, The Netherlands
H. Bloemen
Affiliation:
SRON-Utrecht, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
W. Hermsen
Affiliation:
SRON-Utrecht, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
J. Ryan
Affiliation:
Space Science Center, University of New Hampshire, Durham NH 03824, USA
V. Schönfelder
Affiliation:
Max–Planck–Institut für extraterrestrische Physik, 85740 Garching, Germany
P. von Ballmoos
Affiliation:
Centre d’Etude Spatiale des Rayonnements, 31028 Toulouse Cedex, France

Abstract

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26Al radioactivity is believed to originate predominantly from massive stars, ejected into interstellar medium in wind phases and/or supernova events. With its million-year decay time, penetrating γ-rays from 26Al decay measure the massive-star history averaged over a time scale of ≃million years, thus extending times cales accessible otherwise. The COMPTEL 1.809 MeV all-sky data from 5 years of observations show irregularities and features at intermediate latitudes, which may have a more local origin (≃ 1 kpc). We find that the large scale emission can be characterized by a Galactic scale height of ≃ 130 pc, and a Galactocentric scale radius of ≃ 5 kpc, with features from spiral structure. Catalogues from massive-star related objects do not significantly improve the description of COMPTEL data above this. Emission associated with nearby structures such as the Gould Belt, Loop I, or stellar aggregates, is indicated, yet cannot be clearly detected. Combined with our imaging results, this suggests that 26A1 yields from massive star ensembles depend on specifics of those stars and their history. Further 26A1 γ-ray studies are underway to help mapping of the massive star history in the solar vicinity.

Type
Part VI Distant Hot Gas, SXRB Fluctuations, Dust, Gamma-rays
Information
International Astronomical Union Colloquium , Volume 166: The Local Bubble and Beyond , 1997 , pp. 393 - 396
Copyright
Copyright © Springer-Verlag 1998

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