Presolar Graphite: Noble Gases and their Origins

AbstractPresolar graphite contains a 22Ne-rich component called Ne-E(L). Noble gas studies on graphite aggregates and single grains have shown that although a dominant source of the 22Ne is 22Na, 22Ne in the He-shell of asymptotic giant branch stars have also contributed to the Ne-E(L). In addition to novae that have been considered to be a possible source of 22Na, supernovae are a likely source as well. Krypton isotopic ratios of the separates indicate that part of graphite formed in low-mass (≤3 M⊙) asymptotic giant branch stars of low metallicity (Z ≤ 0.006).

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EVOLUTION OF THERMALLY PULSING ASYMPTOTIC GIANT BRANCH STARS. IV. CONSTRAINING MASS LOSS AND LIFETIMES OF LOW MASS, LOW METALLICITY AGB STARS

The Astrophysical Journal ◽

10.1088/0004-637x/790/1/22 ◽

2014 ◽

Vol 790 (1) ◽

pp. 22 ◽

Cited By ~ 54

Author(s):

Philip Rosenfield ◽

Paola Marigo ◽

Léo Girardi ◽

Julianne J. Dalcanton ◽

Alessandro Bressan ◽

...

Keyword(s):

Mass Loss ◽

Asymptotic Giant Branch ◽

Asymptotic Giant Branch Stars ◽

Agb Stars ◽

Low Metallicity ◽

Low Mass ◽

Giant Branch Stars

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Meteoritic Silicon Carbide Grains with Unusual S[CLC]i[/CLC]-Isotopic Compositions: Evidence for an Origin in Low-Mass, Low-Metallicity Asymptotic Giant Branch Stars

The Astrophysical Journal ◽

10.1086/310869 ◽

1997 ◽

Vol 487 (1) ◽

pp. L101-L104 ◽

Cited By ~ 92

Author(s):

P. Hoppe ◽

P. Annen ◽

R. Strebel ◽

P. Eberhardt ◽

R. Gallino ◽

...

Keyword(s):

Silicon Carbide ◽

Asymptotic Giant Branch ◽

Asymptotic Giant Branch Stars ◽

Isotopic Compositions ◽

Low Metallicity ◽

Low Mass ◽

Giant Branch Stars

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Lithium production by thermohaline mixing in low-mass, low-metallicity asymptotic giant branch stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310004539 ◽

2009 ◽

Vol 5 (S268) ◽

pp. 405-410

Author(s):

Richard J. Stancliffe ◽

George C. Angelou ◽

John C. Lattanzio

Keyword(s):

Main Sequence ◽

Asymptotic Giant Branch ◽

Asymptotic Giant Branch Stars ◽

Agb Stars ◽

Low Metallicity ◽

Low Mass ◽

Thermal Pulses ◽

Giant Branch Stars

AbstractWe examine the effects of thermohaline mixing on the composition of the envelopes of low-metallicity asymptotic giant branch (AGB) stars. We have evolved models of 1, 1.5 and 2M⊙ and of metallicity Z = 10−4 from the pre-main sequence to the end of the thermal pulsing asymptotic giant branch with thermohaline mixing applied throughout the simulations. We find that the small amount of 3He that remains after the first giant branch is enough to drive thermohaline mixing on the AGB and that the mixing is most efficient in the early thermal pulses, with the efficiency dropping from pulse to pulse. We note a surprising increase in the 7Li abundance, with log10ϵ(7Li) reaching values of over 2.5 in the 1.5M⊙ model. It is thus possible to get stars which are both C- and Li-rich at the same time. We compare our models to measurements of carbon and lithium in carbon-enhanced metal-poor stars which have not yet reached the giant branch. These models can simultaneously reproduced the observed C and Li abundances of carbon-enhanced metal-poor turn-off stars that are Li-rich.

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