Signatures of the /sup 2/2Ne Neutron source in red giants and planetary nebulae

Journal Article · Sat Apr 15 04:00:00 EST 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156066· OSTI ID:7089220

Scalo, J M

The operation of the /sup 2/2Ne(..cap alpha.., N)/sup 2/5Mg neutron source should affect the relative abundances of the Mg isotopes and the elemental abundances of Mg and Ne in red giants which exhibit s-process enhancements and in planetary nebulae whose progenitors were peculiar red giants. The predicted abundance changes as a function of s-process enhancement are derived using the published s-process claculations for double shell source models of Truran and Iben. Similar results are expected for other mixing scenarios. Available data show no indication of a correlation of Mg expected for other mixing sceanarios. Available data show no indication of a correlation of Mg abundance with s-process elements. If the progenitors of planetary nebulae are cool carbon stars, then the absence of Ne enhancements in planetary nebulae implies either that all the /sup 2/2Ne is burned during helium-shell flashes, requiring very high temperatures, or that that /sup 1/3C(..cap alpha..,n)/sup 1/6O reaction is the neutron source in most cool carbon stars. Future observations of Mg isotopic ratios in Ba and SC stars using molecular rotational lines of MgH can settle the question of whether /sup 2/2Ne was the neutron source in these stars. Several lines of evidence suggest that /sup 2/2Ne is the neutron source in intermediate-mass (approx.3--8 M/sub sun/) stars which have contributed most of the solar system material, but not in low-mass (approx.1--2 M/sub sun/) stars which comprise most of the peculiar red giants.

• Research Organization: University of Texas at Austin
• OSTI ID: 7089220
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 221:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
ALKALINE EARTH METALS
BARYONS
ELEMENTARY PARTICLES
ELEMENTS
EVEN-EVEN NUCLEI
FERMIONS
GIANT STARS
HADRONS
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MAGNESIUM
METALS
NEBULAE
NEON 22
NEON ISOTOPES
NEUTRONS
NUCLEAR REACTIONS
NUCLEI
NUCLEONS
NUCLEOSYNTHESIS
PLANETARY NEBULAE
RED GIANT STARS
S PROCESS
STABLE ISOTOPES
STAR EVOLUTION
STARS