Radioactive 26Al from massive stars in the Galaxy

Abstract

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.

The next-generation liquid-scintillator neutrino observatory LENA

“…Galactic SNe occur a few times per century as implied by SN statistics of external galaxies [77][78][79], the historical record [80,81], and the galactic abundance of the unstable isotope 26 Al measured with the INTE-GRAL gamma-ray observatory [82]. The low-energy neutrino sky has been systematically watched since 30 June 1980 when the Baksan Scintillator Telescope took up operation.…”

Using population synthesis of massive stars to study the interstellar medium near OB associations

“…The COMPTEL instrument aboard the Compton Gamma Ray Observatory (CGRO) has mapped the 26 Al emission at 1809 keV in a 9-year full sky survey. From a comparison between the image morphology and the known spiral arm tangents and regions of star formation, one can deduce that massive stars dominate the Galactic 26 Al production, and that the contribution from novae and AGB stars must be relatively minor (Diehl et al 1995;Knödlseder et al 1999;Plüschke 2001;Prantzos & Diehl 1996;Diehl et al 2006). Localized groups of massive stars in star-forming regions such as Cygnus and Orion emit clear 26 Al signals, and these regions provide an important contribution to the total amount of 26 Al present in the Milky Way, and it is therefore important to understand these basic building blocks.…”

Absolute determination of theNa22(p,γ)Sallaska1, Wrede2, Garcı́a3 et al. 2011Phys. Rev. C255340View full textAdd to dashboardCite

“…Indeed, this isotope has been observed in the Galaxy [6], but its long half life precludes the identification of its progenitor, and novae are only expected to make a secondary contri-bution to its Galactic abundance [7,8]. Other gammaray emitters can provide more direct constraints on nova models [9].…”