Aluminum‐, Calcium‐ and Titanium‐rich Oxide Stardust in Ordinary Chondrite Meteorites

Nittler, L. R.; Alexander, Conel M. O'd.; Gallino, R.; Hoppe, P.; Nguyen, A. N.; Stadermann, F. J.; Zinner, E.

doi:10.1086/589430

Cited by 181 publications

(298 citation statements)

References 118 publications

(352 reference statements)

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“…The origin of the 18 O-enriched Group 4 grains is more ambiguous than the other grains. However, multi-element isotopic compositions of a few Group 4 oxide (Nittler et al 2008) and silicate (Vollmer, Hoppe & Brenker 2008) grains strongly support a supernova origin for the majority of these grains. A supernova origin is also most likely for two strongly-17 O-depleted grains as well (Nittler et al 1998;Messenger, Keller & Lauretta 2005, Figure 1).…”

Section: O-rich Presolar Stardustmentioning

confidence: 94%

On the Mass and Metallicity Distributions of the Parent AGB Stars of O-Rich Presolar Stardust Grains

Nittler¹

2009

Publ. – Astron. Soc. Aust

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Presolar grains in meteorites formed in a sample of Asymptotic Giant Branch (AGB) stars that ended their lives within ≈1 Gyr of the origin of the Solar System 4.6 Gyr ago. The O-isotopic compositions of presolar O-rich stardust reflect the masses and metallicities of their parent stars. We present simple Monte Carlo simulations of the parent AGB stars of presolar grains. Comparison of model predictions with the grain data allow some broad conclusions to be drawn: (1) Presolar O-rich grains formed in AGB stars of mass ∼1.15-2.2 M . The upper-mass cutoff reflects dredge-up of C in more massive AGB stars, leading to C-rich dust rather than O-rich, but the lack of grains from intermediate-mass AGB stars (>4 M ) is a major puzzle; (2) The grain O-isotopic data are reproduced well if the Galaxy in presolar times was assumed to have a moderate age-metallicity relationship, but with significant metallicity scatter for stars born at the same time; (3) The Sun appears to have a moderately low metallicity for its age and/or unusual 17 O/ 16 O and 18 O/ 16 O ratios for its metallicity; and (4) The Solar 17 O/ 18 O ratio, while unusual relative to present-day molecular clouds and protostars, was not atypical for the presolar disk and does not require self-pollution of the protosolar molecular cloud by supernova ejecta.

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Section: O-rich Presolar Stardustmentioning

confidence: 94%

On the Mass and Metallicity Distributions of the Parent AGB Stars of O-Rich Presolar Stardust Grains

Nittler¹

2009

Publ. – Astron. Soc. Aust

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“…This standard picture is challenged by a large amount of abundance determinations (see for example Brown & Wallerstein 1989;Gratton et al 2000;Charbonnel 2004;Grundahl et al 2002) in field-and globular cluster low-mass giant stars, showing very low 12 C/ 13 C ratios, sometimes almost reaching the equilibrium value of the CN cycle (∼3.5). Anomalies in the C and O isotopes were found also in pre-solar C-rich and O-rich grains of stellar origin, preserved in meteorites (for example Amari et al 2001;Nittler et al 2008). In particular, Al 2 O 3 grains reveal remarkable 18 O destruction (Nittler et al 1997).…”

Section: Introductionmentioning

confidence: 94%

Carbon and oxygen isotopic ratios in Arcturus and Aldebaran

Abia

Palmerini

Busso

et al. 2012

A&A

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Context. We re-analyzed the carbon and oxygen isotopic ratios in the atmospheres of the two bright K giants Arcturus (α Boo) and Aldebaran (α Tau). Aims. These stars are in the evolutionary stage following the first dredge-up (FDU). Previous determinations (dating back more than 20 years) of their 16 O/ 18 O ratios showed a rough agreement with FDU expectations; however, the estimated 16 O/ 17 O and 12 C/ 13 C ratios were lower than in the canonical predictions for red giants. Today these anomalies are interpreted as signs of the occurrence of non-convective mixing episodes. We therefore re-investigated this problem to verify whether the observed data can be reproduced in this scenario and if the fairly well determined properties of the two stars can help us in fixing the uncertain parameters that characterize non-convective mixing and in constraining its physical nature. Methods. We used high-resolution infrared spectra from the literature to derive the 12 C/ 13 C and 16 O/ 17 O/ 18 O ratios from CO molecular lines near 5 μm, using the local termodynamic equilibrium (LTE) spectral synthesis method. We made use of the recently published ACE-FTS atlas of the infrared solar spectrum for constructing an updated atomic and molecular line lists in this spectral range. We also reconsidered the determination of the stellar parameters to build the proper atmospheric and evolutionary models. Results. We found that both the C and the O isotopic ratios for the two stars considered actually disagree with pure FDU predictions. This reinforces the idea that non-convective transport episodes occurred in these stars. By reproducing the observed elemental and isotopic abundances with the help of parametric models for the coupled occurrence of nucleosynthesis and mass circulation, we derived constraints on the properties of non-convective mixing, providing information on the so far elusive physics of these phenomena. We find that very slow mixing, like that associated to diffusive processes, is incapable of explaining the observed data, which require a fast transport. Circulation mechanisms with speeds intermediate between those typical of diffusive and convective mixing are necessary. We conclude with a word of caution on the conclusions possible at this stage however, as the parameters for the mass transport are fairly sensitive to the stellar mass and initial composition. At least for α Boo, reducing the uncertainty still remaining on these data would be highly desirable.

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“…This result from meteorite studies now gets some support by our analysis of the ALMA data, confirming that a fraction of the aluminium is still present in its gaseous form after its passage through the dust formation region. At least for a few silicate grains, the meteoretic studies show that the aluminium oxides are at the core of the silicate grain suggesting that Al 2 O 3 is the first solid to form in the CSE (Nittler et al 2008;Vollmer et al 2006). Both crystalline and amorphous Al 2 O 3 enclosures have been detected (Stroud et al 2004).…”

Section: Aluminium Depletion Into Grainsmentioning

confidence: 99%

Study of the aluminium content in AGB winds using ALMA

Decin

Richards

Waters

et al. 2017

A&A

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Context. The condensation of inorganic dust grains in the winds of evolved stars is poorly understood. As of today, it is not yet known which molecular clusters form the first dust grains in oxygen-rich (C/O < 1) asymptotic giant branch (AGB) winds. Aluminium oxides and iron-free silicates are often put forward as promising candidates for the first dust seeds. Aims. We aim to constrain the dust formation histories in the winds of oxygen-rich AGB stars. Methods. We obtained Atacama Large Millimeter/sub-millimeter array (ALMA) observations with a spatial resolution of 120 × 150 mas tracing the dust formation region of the low mass-loss rate AGB star, R Dor, and the high mass-loss rate AGB star, IK Tau. We detected emission line profiles of AlO, AlOH, and AlCl in the ALMA data and used these line profiles to derive a lower limit of atomic aluminium incorporated in molecules. This constrains the aluminium budget that can condense into grains. Results. Radiative transfer models constrain the fractional abundances of AlO, AlOH, and AlCl in IK Tau and R Dor. We show that the gas-phase aluminium chemistry is completely different in both stars with a remarkable difference in the AlO and AlOH abundance stratification. The amount of aluminium locked up in these three molecules is small, ≤1.1 × 10 −7 w.r.t. H 2 , for both stars, i.e. only ≤2% of the total aluminium budget. An important result is that AlO and AlOH, which are the direct precursors of alumina (Al 2 O 3 ) grains, are detected well beyond the onset of the dust condensation, which proves that the aluminium oxide condensation cycle is not fully efficient. The ALMA observations allow us to quantitatively assess the current generation of theoretical dynamical-chemical models for AGB winds. We discuss how the current proposed scenario of aluminium dust condensation for low mass-loss rate AGB stars within a few stellar radii from the star, in particular for R Dor and W Hya, poses a challenge if one wishes to explain both the dust spectral features in the spectral energy distribution (SED) in interferometric data and in the polarized light signal. In particular, the estimated grain temperature of Al 2 O 3 is too high for the grains to retain their amorphous structure. We advocate that large gas-phase (Al 2 O 3 ) n clusters (n > 34) can be the potential agents of the broad 11 µm feature in the SED and in the interferometric data and we propose potential formation mechanisms for these large clusters.

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Aluminum‐, Calcium‐ and Titanium‐rich Oxide Stardust in Ordinary Chondrite Meteorites

Cited by 181 publications

References 118 publications

On the Mass and Metallicity Distributions of the Parent AGB Stars of O-Rich Presolar Stardust Grains

On the Mass and Metallicity Distributions of the Parent AGB Stars of O-Rich Presolar Stardust Grains

Carbon and oxygen isotopic ratios in Arcturus and Aldebaran

Study of the aluminium content in AGB winds using ALMA

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