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The Role of Massive Agb Stars in the Early Solar System Composition
Josep M. Trigo-Rodriguez, Domingo Anibal Garcia-Hernandez, Maria Lugaro +4
We demonstrate that a massive asymptotic giant branch (AGB) star is a good candidate as the main source of short-lived radionuclides in the early solar system. Recent identificatio…
The impact of the 18F(a,p)21Ne reaction on fluorine production in AGB stars
Amanda I. Karakas, Hye Young Lee, Maria Lugaro +2
The recent experimental evaluation of the 18F(a,p)21Ne reaction rate, when considering its associated uncertainties, presented significant differences compared to the theoretical H…
Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae
Amanda I. Karakas, Mark A. van Raai, Maria Lugaro +2
Type I planetary nebulae (PNe) have high He/H and N/O ratios and are thought to be descendants of stars with initial masses of ~3-8Msun. These characteristics indicate that the pro…
Modelling the evolution and nucleosynthesis of carbon-enhanced metal-poor stars
O. R. Pols, R. G. Izzard, M. Lugaro +1
We present the results of binary population simulations of carbon-enhanced metal-poor (CEMP) stars. We show that nitrogen and fluorine are useful tracers of the origin of CEMP star…
Fluorine in carbon-enhanced metal-poor stars: a binary scenario
M. Lugaro, S. E. de Mink, R. G. Izzard +8
A super-solar fluorine abundance was observed in the carbon-enhanced metal-poor (CEMP) star HE 1305+0132 ([F/Fe] = +2.90, [Fe/H] = -2.5). We propose that this observation can be ex…
New reaction rate for 16O(p,gamma)17F and its influence on the oxygen isotopic ratios in massive AGB stars
C. Iliadis, C. Angulo, P. Descouvemont +2
The 16O(p,gamma)17F reaction rate is revisited with special emphasis on the stellar temperature range of T=60-100 MK important for hot bottom burning in asymptotic giant branch (AG…
Reaction rate uncertainties and 26Al in AGB silicon carbide stardust
M. A. van Raai, M. Lugaro, A. I. Karakas +1
Stardust is a class of presolar grains each of which presents an ideally uncontaminated stellar sample. Mainstream silicon carbide (SiC) stardust formed in the extended envelopes o…
The impact of the 18F(a,p)21Ne reaction on asymptotic giant branch nucleosynthesis
Amanda Karakas, Hye Young Lee, Maria Lugaro +2
We present detailed models of low and intermediate-mass asymptotic giant branch (AGB) stars with and without the 18F(a,p)21Ne reaction included in the nuclear network, where the ra…
On the solar abundance of indium
N. Vitas, I. Vince, M. Lugaro +3
The generally adopted value for the solar abundance of indium is over six times higher than the meteoritic value. We address this discrepancy through numerical synthesis of the 451…
Stellar population synthesis of post-AGB stars: the s-process in MACHO47.2496.8
A. Bonacic Marinovic, M. Lugaro, M. Reyniers +1
The low-metallicity RV Tauri star MACHO47.2496.8, recently discovered in the Large Magellanic Cloud, is highly enriched in carbon and heavy elements produced by the slow neutron ca…
Reaction rate uncertainties and the operation of the NeNa and MgAl chains during HBB in intermediate-mass AGB stars
R. G. Izzard, M. Lugaro, A. I. Karakas +2
We test the effect of proton-capture reaction rate uncertainties on the abundances of the Ne, Na, Mg and Al isotopes processed by the NeNa and MgAl chains during hot bottom burning…
Germanium Production in Asymptotic Giant Branch stars: Implications for Observations of Planetary Nebulae
Amanda Karakas, Maria Lugaro, Roberto Gallino
Observations of planetary nebulae (PNe) by Sterling, Dinerstein and Bowers have revealed abundances in the neutron-capture element Germanium (Ge) from solar to factors of 3 -- 10 a…
On the asymptotic giant branch star origin of peculiar spinel grain OC2
M. Lugaro, A. I. Karakas, L. R. Nittler +4
Microscopic presolar grains extracted from primitive meteorites have extremely anomalous isotopic compositions revealing the stellar origin of these grains. The composition of pres…
Population synthesis of s-process element enhanced stars: Constraining the 13C efficiency
A. Bonacic Marinovic, R. G. Izzard, M. Lugaro +1
We study s-process element abundance ratios in stars by carrying out stellar population synthesis, using a rapid synthetic stellar evolution code which includes an up-to-date treat…
Cosmological implications of dwarf spheroidal chemical evolution
Yeshe Fenner, Brad K. Gibson, Roberto Gallino +1
The chemical properties of dwarf spheroidals in the local group are shown to be inconsistent with star formation being truncated after the reionization epoch (z~8). Enhanced levels…
The Uncertainties in the 22Ne + alpha-capture Reaction Rates and the Production of the Heavy Magnesium Isotopes in Asymptotic Giant Branch Stars of Intermediate Mass
A. Karakas, M. Lugaro, M. Wiescher +2
We present new rates for the 22Ne(alpha, n)25Mg and 22Ne(alpha,gamma)26Mg reactions, with uncertainties that have been considerably reduced compared to previous estimates, and we s…
What we do and do not know about the s-process
J. C. Lattanzio, M. A. Lugaro
AGB stars are the source for the main component of the -process. Here we discuss both the properties which are reasonably well known and those which still suffer from substantia…
The effect of the 19F(alpha,p)22Ne reaction rate uncertainty on the yield of fluorine from Wolf-Rayet Stars
R. J. Stancliffe, M. Lugaro, C. Ugalde +3
In the light of recent recalculations of the \el{19}{F}(alpha,p)\el{22}{Ne} reaction rate we present results of the expected yield of \el{19}{F} from Wolf-Rayet (WR) stars. We have…
Constraints on AGB models from the heavy-element composition of presolar SiC grains
M. Lugaro, A. M. Davis, R. Gallino +2
Presolar SiC grains formed around Asymptotic Giant Branch (AGB) stars during their carbon-rich phase and contain heavy elements in trace amounts showing the signature of the slow n…
HR4049: signature of nova nucleosynthesis ?
Maria Lugaro, Onno Pols, Amanda I. Karakas +1
The post-Asymptotic Giant Branch (AGB) star HR4049 is in an eccentric binary system with a relatively short period probably surrounded by a dusty circumbinary disk. Extremely anoma…
Reaction Rates Uncertainties and the Production of F19 in AGB Stars
Maria Lugaro, Claudio Ugalde, Amanda I. Karakas +4
We present nucleosynthesis calculations and the resulting 19F stellar yields for a large set of models with different masses and metallicity. We find that the production of fluorin…
The s-Process in Rotating Asymptotic Giant Branch Stars
Falk Herwig, Norbert Langer, Maria Lugaro
(abridged) We model the nucleosynthesis during the thermal pulse phase of a rotating, solar metallicity AGB star of 3M_sun. Rotationally induced mixing during the thermal pulses pr…
s-Process Nucleosynthesis in AGB Stars: A Test for Stellar Evolution
Maria Lugaro, Falk Herwig, John C. Lattanzio +2
[abridged] We study the s-process in AGB stars using three different stellar evolutionary models computed for a 3Msun and solar metallicity star. First we investigate the formation…
Could SiC A+B grains have originated in a post-AGB thermal pulse?
Falk Herwig, Sachiko Amari, Maria Lugaro +1
The carbon and nitrogen isotopic ratios of pre-solar SiC grains of type A+B suggest a proton-limited nucleosynthetic process as encountered, for instance, during the very late ther…