Radioactive 26Al from massive stars in the Galaxy
Roland Diehl(1), Hubert Halloin(1), Karsten Kretschmer(1), Giselher G. Lichti(1), Volker Schönfelder(1), Andrew W. Strong(1), Andreas von Kienlin(1), Wei Wang(1), Pierre Jean(2), Jürgen Knödlseder(2), Jean-Pierre Roques(2), Georg Weidenspointner(2), Stephane Schanne(3), Dieter H. Hartmann(4), Christoph Winkler(5) and Cornelia Wunderer(6)
Gamma-rays from radioactive 26Al (half-life 7.2 * 10^5 years) provide a 'snapshot' view of continuing nucleosynthesis in the Galaxy(1). The Galaxy is relatively transparent to such -rays, and emission has been found concentrated along its plane(2). This led to the conclusion(1) that massive stars throughout the Galaxy dominate the production of 26Al. On the other hand, meteoritic data show evidence for locally produced 26Al, perhaps from spallation reactions in the protosolar disk3, 4, 5. Furthermore, prominent -ray emission from the Cygnus region suggests that a substantial fraction of Galactic 26Al could originate in localized star-forming regions. Here we report high spectral resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide origin. We determine a present-day equilibrium mass of 2.8 ( 0.8) solar masses of 26Al. We use this to determine that the frequency of core collapse (that is, type Ib/c and type II) supernovae is 1.9 ( 1.1) events per century.
1. Max-Planck-Institut für extraterrestrische Physik, D-85748 Garching, Germany
2. Centre d'Etude Spatiale des Rayonnements and Université Paul Sabatier, 31028 Toulouse, France
3. DSM/DAPNIA/Service d'Astrophysique, CEA Saclay, 91191 Gif-Sur-Yvette, France
4. Clemson University, Clemson, South Carolina 29634-0978, USA
5. ESA/ESTEC, SCI-SD 2201 AZ Noordwijk, The Netherlands
6. Space Sciences Laboratory, Berkeley, California 94720, USA
Correspondence to: Roland Diehl(1) Correspondence and requests for materials should be addressed to R.D. (Email: rod@mpe.mpg.de). |
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