AGB Stars and the Observed Abundance of Neon in Planetary Nebulae

Karakas, Amanda I.; Lattanzio, John C.

doi:10.1071/as03059

Cited by 64 publications

(104 citation statements)

References 25 publications

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“…In the hottest models, 26 Mg production is by-passed by 26 Al(p, γ) 27 Si(β + ) 27 Al. We also confirm the results of Karakas & Lattanzio (2003) and Denissenkov & Herwig (2003) that the production of heavy magnesium isotopes by HBB always leads to higher 25 Mg. The 3DUP enriches the envelope with 22 Ne and 25,26 Mg and at low metallicity (Z < ∼ 10 −3 ) the effects are even stronger than those induced by changing T env .…”

Section: Yields Resultssupporting

confidence: 78%

Evolution of massive AGB stars

Siess

2010

A&A

186

323

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Aims. We present the first simulations of the full evolution of super-AGB stars through the entire thermally pulsing AGB phase. We analyse their structural and evolutionary properties and determine the first SAGB yields.Methods. Stellar models of various initial masses and metallicities were computed using standard physical assumptions which prevents the third dredge-up from occurring. A postprocessing nucleosynthesis code was used to compute the SAGB yields, to quantify the effect of the third dredge-up (3DUP), and to assess the uncertainties associated with the treatment of convection.Results. Owing to their massive oxygen-neon core, SAGB stars suffer weak thermal pulses, have very short interpulse periods and develop very high temperatures at the base of their convective envelope (up to 140 × 10 8 K), leading to very efficient hot bottom burning. SAGB stars are consequently heavy manufacturers of 4 He, 13 C, and 14 N. They are also able to inject significant amounts of 7 Li, 17 O, 25 Mg, and 26,27 Al in the interstellar medium. The 3DUP mainly affects the CNO yields, especially in the lower metallicity models. Our post-processing simulations also indicate that changes in the temperature at the base of the convective envelope, which would result from a change in the efficiency of convective energy transport, have a dramatic impact on the yields and represent another major source of uncertainty.

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Section: Yields Resultssupporting

confidence: 78%

Evolution of massive AGB stars

Siess

2010

A&A

186

323

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“…3 the N/O ratio has been plotted against the C/O ratio for those PNe with carbon abundances. The predicted values of these ratios (Karakas 2003) as a function of stellar mass for initial values of Z = 0.004, 0.008 and 0.02 are shown as points connected by dashed lines. It may be seen that a very similar picture emerges as that drawn from the N/O vs. He/H plot.…”

Section: The Carbon Abundancementioning

confidence: 99%

“…The two elliptical PNe which have a high N/O ratio and thus lie close to the six bipolar nebulae are M1-42 and NGC 5315. The abundances predicted by Karakas (2003) for stars of different initial masses are labeled with numbers in the figure indicating the masses used. These masses are connected with lines for each of the three different values of heavy element abundance Z.…”

Section: Helium Vs N/omentioning

confidence: 99%

“…Models referring to evolution on the AGB have been made by several authors, e.g. Marigo et al (2003) and Karakas (2003). The latter models predict changes in the chemical composition which have occurred during the evolution and which have been brought to the surface Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.…”

Section: Introductionmentioning

confidence: 99%

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Planetary nebulae abundances and stellar evolution II

Pottasch

Bernard─Salas

2010

A&A

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Context. In recent years mid-and far infrared spectra of planetary nebulae have been analysed and lead to more accurate abundances. It may be expected that these better abundances lead to a better understanding of the evolution of these objects. Aims. The observed abundances in planetary nebulae are compared to those predicted by the models of Karakas (2003, Thesis, Monash Univ. Melbourne) in order to predict the progenitor masses of the various PNe used. The morphology of the PNe is included in the comparison. Since the central stars play an important role in the evolution, it is expected that this comparison will yield additional information about them. Methods. First the nitrogen/oxygen ratio is discussed with relation to the helium/hydrogen ratio. The progenitor mass for each PNe can be found by a comparison with the models of Karakas. Then the present luminosity of the central stars is determined in two ways: first by computing the central star effective temperature and radius, and second by computing the nebular luminosity from the hydrogen and helium lines. This luminosity is also a function of the initial mass so that these two values of initial mass can be compared. Results. Six of the seven bipolar nebulae can be identified as descendants of high mass stars (4−6 M ) while the seventh is ambiguous. Most of the elliptical PNe have central stars which descend from low initial mass stars, although there are a few caveats which are discussed. There is no observational evidence for a higher mass for central stars which have a high carbon/oxygen ratio. The evidence provided by the abundance comparison with the models of Karakas is consistent with the HR diagram to which it is compared. In the course of this discussion it is shown how "optically thin" nebulae can be separated from those which are "optically thick".

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“…However, the major stellar codes (e.g. the Australian MSSSP, or the Italian FRANEC) can now be run in individual control cases using the whole reaction set [88] [89], thereby providing the nodes of a grid. Stellar parameters for other cases can then be deduced by suitable interpolations [89].…”

Section: Standard Modelsmentioning

confidence: 99%

Short-lived nuclei in the early Solar System: Possible AGB sources

et al. 2006

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The abundances of short-lived radionuclides in the early solar system (ESS) are reviewed, as well as the methodology used in determining them. These results are compared with the inventory estimated for a uniform galactic production model. It is shown that, to within a factor of two, the observed abundances of 238 U, 235 U, 232 Th, 244 Pu, 182 Hf, 146 Sm, and 53 Mn are roughly compatible with long-term galactic nucleosynthesis. 129 I is an exception, with an ESS inventory much lower than expected from uniform production. The isotopes 107 Pd, 60 Fe, 41 Ca, 36 Cl, 26 Al, and 10 Be require late addition to the protosolar nebula. 10 Be is the product of energetic particle irradiation of the solar system as most probably is 36 Cl. Both of these nuclei appear to be present when 26 Al is absent. A late injection by a supernova (SN) cannot be responsible for most of the short-lived nuclei without excessively producing 53 Mn; it can however be the source of 53 Mn itself and possibly of 60 Fe. If a late SN injection is responsible for these two nuclei, then there remains the problem of the origin of 107 Pd and several other isotopes. Emphasis is given to an AGB star as a source of many of the nuclei, including 60 Fe; this possibility is explored with a new generation of stellar models. It is shown that if the dilution factor (i.e. the ratio of the contaminating mass to the solar parental cloud mass) is f 0 ∼ 4×10 −3 , a reasonable representation for many nuclei is obtained; this requires that ( 60 Fe/ 56 Fe) ESS ∼ 10 −7 to 2×10 −6 . The nuclei produced by an AGB source do not include 53 Mn, 10 Be or 36 Cl if it is very abundant. The role of irradiation is discussed with regard to 26 Al, 36 Cl and 41 Ca, and the estimates of bulk solar abundances of these isotopes are commented on. The conflict between various scenarios is emphasized as well as the current absence of an astrophysically plausible global interpretation for all the existing data. Examination of abundances for the actinides indicates that a quiescent interval of ∼ 10 8 years is required for actinide group production. This is needed in order to explain the data on 244 Pu and the new bounds on 247 Cm. Because this quiescent interval is not compatible with the 182 Hf data, a separate type of r-process event is needed for at least the actinides, distinct from the two types that have previously been identified. The apparent coincidence of the 129 I and trans-actinide time scales suggests that the last heavy r contribution was from an r-process that produced very heavy nuclei but without fission recycling so that the yields at Ba and below (including I) were governed by fission.

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AGB Stars and the Observed Abundance of Neon in Planetary Nebulae

Cited by 64 publications

References 25 publications

Evolution of massive AGB stars

Evolution of massive AGB stars

Planetary nebulae abundances and stellar evolution II

Short-lived nuclei in the early Solar System: Possible AGB sources

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