Radioactive 26Al from massive stars in the Galaxy.
Gamma-rays from radioactive 26Al (half-life approximately 7.2 x 10(5) years) provide a 'snapshot' view of continuing nucleosynthesis in the Galaxy. The Galaxy is relatively transparent to such gamma-rays, and emission has been found concentrated along its plane. This led to the conclusion 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 disk. Furthermore, prominent gamma-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.
Diehl
Roland
R
Max-Planck-Institut für extraterrestrische Physik, D-85748 Garching, Germany. rod@mpe.mpg.de
Halloin
Hubert
H
Kretschmer
Karsten
K
Lichti
Giselher G
GG
Schönfelder
Volker
V
Strong
Andrew W
AW
von Kienlin
Andreas
A
Wang
Wei
W
Jean
Pierre
P
Knödlseder
Jürgen
J
Roques
Jean-Pierre
JP
Weidenspointner
Georg
G
Schanne
Stephane
S
Hartmann
Dieter H
DH
Winkler
Christoph
C
Wunderer
Cornelia
C