Astrophysics with Presolar Stardust

Clayton, Donald D.; Nittler, L. R.

doi:10.1146/annurev.astro.42.053102.134022

Cited by 294 publications

(251 citation statements)

References 171 publications

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“…The adopted grain size range is motivated by studies on pre-solar grains (e.g. Nittler et al 1997;Daulton et al 2003;Clayton & Nittler 2004) and detailed radiative modeling of evolved stars such as IRAS 17150-3224 and HD 161796 (Meixner et al 2002). The default model corresponds to model 1 in Table 1.…”

Section: Parameter Study: Results and Discussionmentioning

confidence: 99%

Water ice growth around evolved stars

Dijkstra

Dominik

Bouwman

et al. 2006

A&A

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We present combined radiative transfer and H 2 O ice formation calculations for the dusty envelopes of oxygen-rich evolved stars. We study the effects of various (circum-)stellar parameters on the spectral energy distribution of these stars, their infrared spectral water ice features at 3 µm and in the 30−100 µm region, and the properties of (water ice on) the grains in their envelopes. We also study the ice formation process as a function of stellar evolution for a star with an initial mass of 5 M , which is followed during the AGB, post-AGB and planetary nebula (PN) phase. We find that its water ice features probe its evolution. Both crystalline and amorphous water ice form in our models. The 43 and 62 µm crystalline water ice features are most prominent during the post-AGB phase, and only modestly or not present during the AGB and PN phase, in agreement with observations. The strength of the 3, 43 and 62 µm water ice features decreases with decreasing initial mass of the star. The total amount of ice predicted (a few percent of the total dust mass) also agrees with observations, but the crystalline ice mass fraction is consistently about two orders of magnitude lower. This is mainly due to efficient amorphization by interstellar UV photons, and leads to weaker 43 and 62 µm crystalline water ice features than observed. The intensity of the interstellar UV radiation field strongly influences the strength of these features. We discuss several means to increase the crystalline water ice mass, and hence their strength. The strength of the features increases dramatically when the mass-loss rate over luminosity ratio of the star,Ṁ/L, is large in the AGB phase. In case of the post-AGB star HD 161796 we demonstrate that this indeed leads to the correct crystalline ice mass fraction and feature strengths. Also, the formation of clumps in the AGB wind provides high densities to stimulate the formation of (crystalline) ice. For stars with high initial masses, it additionally provides sufficient shielding from interstellar UV radiation to keep ice crystalline during the post-AGB and PN phase. Axisymmetric mass loss on the AGB provides favorable conditions for the formation and preservation of water ice, and crystalline water ice in particular, as well. In contrast we find that post-AGB crystallization of AGB produced amorphous ice is unimportant for increasing the crystalline water ice mass around 5 M stars.

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Section: Parameter Study: Results and Discussionmentioning

confidence: 99%

Water ice growth around evolved stars

Dijkstra

Dominik

Bouwman

et al. 2006

A&A

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“…As for the term "sapphire", we will avoid it in the following, since it refers to α- Nittler 1997;Clayton & Nittler 2004;Hoppe 2004). However, it has so far not been possible to set any strong constrain on the polytype of Al 2 O 3 by presolar grain studies (which is a problem, since many polytypes of Al 2 O 3 exist -see, e.g., Tamanai et al 2009).…”

Section: Hot Corundum and The 13 μM Bandmentioning

confidence: 99%

Optical constants of refractory oxides at high temperatures

Zeidler

Posch

Mutschke

2013

A&A

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Context. Many cosmic dust species, among them refractory oxides, form at temperatures higher than 300 K. Nevertheless, most astrophysical studies are based on the room-temperature optical constants of solids, such as corundum and spinel. A more realistic approach is needed for these materials, especially in the context of modeling late-type stars. Aims. We aimed at deriving sets of optical constants of selected, astrophysically relevant oxide dust species with high melting points. Methods. A high-temperature, high-pressure cell and a Fourier-transform spectrometer were used to measure reflectance spectra of polished samples. For corundum (α-Al 2 O 3 ), spinel (MgAl 2 O 4 ), and α-quartz (SiO 2 ), temperature-dependent optical constants were measured from 300 K up to more than 900 K. Small particle spectra were also calculated from these data. Results. All three examined oxides show a significant temperature dependence of their mid-IR bands. For the case of corundum, we find that the 13 μm emission feature -seen in the IR spectra of many AGB stars -can very well be assigned to this mineral species. The best fit of the feature is achieved with oblate corundum grains at (mean) temperatures around 550 K. Spinel remains a viable carrier of the 13 μ feature as well, but only for T < 300 K and nearly spherical grain shapes. Under such circumstances, spinel grains may also account for the 31.8 μm band that is frequently seen in sources of the 13 μm feature and which has not yet been identified with certainty.

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“…A major uncertainty in the 60 Fe production lies in the neutron capture cross sections of both 59 [221]; they obtain < σ >(30 keV)( 59 Fe) = 22.5 mbarn. We adopt here these recent estimates, but we verified that, if we had instead used the old cross sections for both 59 Fe and 60 Fe, our production of 60 Fe (as given in Tables 3, 4) would have been reduced by a factor ≈ 1.8 for all the M = 1.5 and 3 M ⊙ models, and by a factor of ∼ 1.2 for the M = 5M ⊙ models. We conclude that variations of the neutron capture cross sections cannot change our predictions by more than a factor of 2.…”

Section: Estimating the 60 Fe Inventorymentioning

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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Astrophysics with Presolar Stardust

Cited by 294 publications

References 171 publications

Water ice growth around evolved stars

Water ice growth around evolved stars

Optical constants of refractory oxides at high temperatures

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

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