Dust cleansing of star-forming gas: II. Did late accretion flows change the chemical composition of the solar atmosphere?

Gustafsson, Bengt

doi:10.48550/arxiv.1809.02361

Cited by 2 publications

(3 citation statements)

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“…Also, Gustafsson (2018a), found by model calculations that the mechanism would not be effective enough to cleanse most of the gas forming a full cluster from dust, and that turbulence in the cloud would probably strongly reduce the degree of dust-cleansing as a whole. Another possibility studied by Gustafsson (2018b) is that the radiation from the proto-Sun itself partially cleansed the gas to be accreted in the late stages of the star formation process. For this mechanism to work, one has to assume a relatively slow accretion rate (on the order of 0.01 M ⊙ /Myr), active during at least 1 Myr, at a stage so late that the solar convection zone has retracted toward the surface enough to contain only a few percent of the solar mass.…”

Section: The Sun Compared To Solar Twinsmentioning

confidence: 99%

High-precision stellar abundances of the elements: methods and applications

Nissen

Gustafsson

2018

Astron Astrophys Rev

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Efficient spectrographs at large telescopes have made it possible to obtain high-resolution spectra of stars with high signal-to-noise ratio and advances in model atmosphere analyses have enabled estimates of high-precision differential abundances of the elements from these spectra, i.e. with errors in the range 0.01 -0.03 dex for F, G, and K stars.Methods to determine such high-precision abundances together with precise values of effective temperatures and surface gravities from equivalent widths of spectral lines or by spectrum synthesis techniques are outlined, and effects on abundance determinations from using a 3D non-LTE analysis instead of a classical 1D LTE analysis are considered.The determination of high-precision stellar abundances of the elements have led to the discovery of unexpected phenomena and relations with important bearings on the astrophysics of galaxies, stars, and planets, i.e. i) Existence of discrete stellar populations within each of the main Galactic components (disk, halo, and bulge) providing new constraints on models for the formation of the Milky Way. ii) Differences in the relation between abundances and elemental condensation temperature for the Sun and solar twins suggesting dust-cleansing effects in proto-planetary disks and/or engulfment of planets by stars; iii) Differences in chemical composition between binary star components and between members of open or globular clusters showing that star-and cluster-formation processes are more complicated than previously thought; iv) Tight relations between some abundance ratios and age for solar-like stars providing new constraints on nucleosynthesis and Galactic chemical evolution models as well as the composition of terrestrial exoplanets.We conclude that if stellar abundances with precisions of 0.01 -0.03 dex can be achieved in studies of more distant stars and stars on the giant and supergiant branches, many more interesting future applications, of great relevance to stellar and galaxy evolution, are probable. Hence, in planning abundance surveys, it is important to carefully balance the need for large samples of stars against the spectral resolution and signal-to-noise ratio needed to obtain high-precision abundances. Furthermore, it is an advantage to work differentially on stars with similar atmospheric parameters, because then a simple 1D LTE analysis of stellar spectra may be sufficient. However, when determining high-precision absolute abundances or differential abundance between stars having more widely different parameters, e.g. metal-poor stars compared to the Sun or giants to dwarfs, then 3D non-LTE effects must be taken into account.

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Section: The Sun Compared To Solar Twinsmentioning

confidence: 99%

High-precision stellar abundances of the elements: methods and applications

Nissen

Gustafsson

2018

Astron Astrophys Rev

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“…We did not consider either the possibility of a change in stellar surface abundances caused by planet engulfment and/or planet formation (Smith et al 2001;Meléndez et al 2009;Ramírez et al 2010). Some theoretical works support the possible modification of stellar abundances through planet formation (e.g., Kunitomo et al 2018;Chambers 2010), (but see also Théado & Vauclair 2012;Gustafsson 2018). However, from an observational point of view, the presence of chemical signatures of planet formation in the spectra of stars is still lively debated (see, e.g., Adibekyan et al 2014, 2017, andreferences therein).…”

Section: Discussionmentioning

confidence: 99%

“…These chronometers can be used, at least, to cross-check the isochronal ages of the stars. One of the most frequently discussed chronometers is the log(R HK ) chromospheric activity indicator (e.g., Mamajek & Hillenbrand 2008;Pace 2013;Lorenzo-Oliveira et al 2016, 2018. We followed the works of Suárez Mascareño et al (2015) and Hojjatpanah et al (2018, in prep.…”

Section: Stellar Ages and Activitymentioning

confidence: 99%

The AMBRE project: searching for the closest solar siblings

Adibekyan

Laverny

Recio–Blanco

et al. 2018

A&A

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Context. Finding solar siblings, that is, stars that formed in the same cluster as the Sun, will yield information about the conditions at the Sun's birthplace. Finding possible solar siblings is difficult since they are spread widely throughout the Galaxy. Aims. We search for solar sibling candidates in AMBRE, the very large spectra database of solar vicinity stars. Methods. Since the ages and chemical abundances of solar siblings are very similar to those of the Sun, we carried out a chemistry-and age-based search for solar sibling candidates. We used high-resolution spectra to derive precise stellar parameters and chemical abundances of the stars. We used these spectroscopic parameters together with Gaia DR2 astrometric data to derive stellar isochronal ages. Gaia data were also used to study the kinematics of the sibling candidates.Results. From the about 17 000 stars that are characterized within the AMBRE project, we first selected 55 stars whose metallicities are closest to the solar value (−0.1 ≤ [Fe/H] ≤ 0.1 dex). For these stars we derived precise chemical abundances of several iron-peak, α-and neutron-capture elements, based on which we selected 12 solar sibling candidates with average abundances and metallicities between −0.03 to 0.03 dex. Our further selection left us with 4 candidates with stellar ages that are compatible with the solar age within observational uncertainties. For the 2 of the hottest candidates, we derived the carbon isotopic ratios, which are compatible with the solar value. HD186302 is the most precisely characterized and probably the most probable candidate of our 4 best candidates.Conclusions. Very precise chemical characterization and age estimation is necessary to identify solar siblings. We propose that in addition to typical chemical tagging, the study of isotopic ratios can give further important information about the relation of sibling candidates with the Sun. Ideally, asteroseismic age determinations of the candidates could solve the problem of imprecise isochronal ages.

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Dust cleansing of star-forming gas: II. Did late accretion flows change the chemical composition of the solar atmosphere?

Cited by 2 publications

References 43 publications

High-precision stellar abundances of the elements: methods and applications

High-precision stellar abundances of the elements: methods and applications

The AMBRE project: searching for the closest solar siblings

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