Title

Radioactive Al-26 measured on LDEF satellite clamps - What is its source?

Authors

Authors

R. Grismore; R. A. Llewellyn; A. Z. Rosen; J. A. Hodge;W. Wright

Comments

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Abbreviated Journal Title

Astropart Phys.

Keywords

Accretion; Aluminum-26; Cosmic-rays; Local interplanetary medium; Supernova remnants; Spallation; INTERSTELLAR-MEDIUM; LUNAR ROCKS; RAY; SPECTRA; GEMINGA; BE-10; DECAY; Astronomy & Astrophysics; Physics, Particles & Fields

Abstract

Since 1984 astrophysicists have speculated on the original source of the Al-26 measured by the HEAO 3 satellite gamma-ray telescope. With a half-life of 717000 years it cannot be primordial, and the Sun cannot produce it. Possible sources suggested have included gamma radiation directly from various astronomical entities, such as novae, supernovae, AGB stars or Wolf-Rayet stars, or radiating particles from some of those sources present in the local interstellar medium. It has also been suggested that some of the Al-26 gamma radiation being observed might be coming from grains produced in nearby supernovae, or from cosmic-ray spallation reactions occurring on heavier atoms in space. These atoms or particles might have been swept down into the local interstellar medium by the solar or stellar winds. Using a multidimensional gamma-ray spectrometer we have measured the disintegration rates of Al-26 on four clamps which flew for 5.8 years on the Long Duration Exposure Facility satellite. Evaluation of possible local internal production of Al-26 by cosmic-rays during the known flight path of the satellite has determined that the observed Al-26 disintegration rates of the four clamps range from 17 to 32 times the rates from local production. Thus. the 26 Al observed is likely from space, confirming earlier discoveries of its presence in the local interstellar medium. Based on our measurements, a tentative maximum value of 0.000052 +/- 0.000006 atoms cm(-3) is derived for the density of 26 Al in near Earth space. (C) 2009 Elsevier B.V. All rights reserved.

Journal Title

Astroparticle Physics

Volume

31

Issue/Number

4

Publication Date

1-1-2009

Document Type

Article

Language

English

First Page

297

Last Page

304

WOS Identifier

WOS:000266336300007

ISSN

0927-6505

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