The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks

Piso, Ana-Maria; Pegues, Jamila; Öberg, Karin I.

doi:10.3847/1538-4357/833/2/203

Cited by 93 publications

(66 citation statements)

References 55 publications

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“…Theoretical studies suggest that the C/O number ratio as well as Mg/Si are important in determining the mineralogy of extraterrestrial planets. While the C/O ratio controls the amount of carbides and silicates formed in planets, the Mg/Si can tell us about the silicate mineralogy (e.g., Bond et al 2010;Madhusudhan et al 2014;Piso et al 2016). For stars with Mg/Si < 1, terrestrial planets will have a magnesium depleted mineralogy different from that of the Earth.…”

Section: LI C and O In Stars With Planetsmentioning

confidence: 99%

High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

Stonkutė

Chorniy

Tautvaišienė

et al. 2020

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Abundances of lithium, carbon, and oxygen have been derived using spectral synthesis for a sample of 249 bright F, G, and K Northern Hemisphere dwarf stars from the high-resolution spectra acquired with the VUES spectrograph at the Molėtai Astronomical Observatory of Vilnius University. The sample stars have metallicities, effective temperatures, and ages between (-0.7 ÷ 0.4) dex, (5000 ÷ 6900) K, (1 ÷ 12) Gyr, accordingly. We confirm a so far unexplained lithium abundance decrease at supersolar metallicities -A(Li) in our sample stars, which drop by 0.7 dex in the [Fe/H] range from +0.10 to +0.55 dex. Furthermore, we identified stars with similar ages, atmospheric parameters, and rotational velocities, but with significantly different lithium abundances, which suggests that additional specific evolutionary factors should be taken into account while interpreting the stellar lithium content. Nine stars with predominantly supersolar metallicities, i.e. about 12 % among 78 stars with C and O abundances determined, have the C/O number ratios larger than 0.65, thus may form carbon-rich rocky planets. Ten planet-hosting stars, available in our sample, do not show a discernible difference from the stars with no planets detected regarding their lithium content.

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Section: LI C and O In Stars With Planetsmentioning

confidence: 99%

High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

Stonkutė

Chorniy

Tautvaišienė

et al. 2020

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“…Static models are more straightforward to couple with chemical kinetics. Recently Piso et al (2015Piso et al ( , 2016 explored the evolution of elemental ratios across icelines in both a static and viscously evolving disk model including the radial drift of ice-coated grains of different sizes. The temperature structure is kept fixed in time in these models.…”

Section: Introductionmentioning

confidence: 99%

Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes

Eistrup

Walsh

Dishoeck

2018

A&A

150

252

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Context. Exoplanet atmospheres are thought be built up from accretion of gas as well as pebbles and planetesimals in the midplanes of planet-forming disks. The chemical composition of this material is usually assumed to be unchanged during the disk lifetime. However, chemistry can alter the relative abundances of molecules in this planet-building material. Aims. To assess the impact of disk chemistry during the era of planet formation. This is done by investigating the chemical changes to volatile gases and ices in a protoplanetary disk midplane out to 30 AU for up to 7 Myr, considering a variety of different conditions, including a physical midplane structure that is evolving in time, and also considering two disks with different masses.Methods. An extensive kinetic chemistry gas-grain reaction network is utilised to evolve the abundances of chemical species over time. Two disk midplane ionisation levels (low and high) are explored, as well as two different makeups of the initial abundances ("inheritance" or "reset"). Results. Given a high level of ionisation, chemical evolution in protoplanetary disk midplanes becomes significant after a few times 10 5 yrs, and is still ongoing by 7 Myr between the H 2 O and the O 2 icelines. Inside the H 2 O iceline, and in the outer, colder regions of the disk midplane outside the O 2 iceline, the relative abundances of the species reach (close to) steady state by 7 Myr. Importantly, the changes in the abundances of the major elemental carbon and oxygen-bearing molecules imply that the traditional "stepfunction" for the C/O ratios in gas and ice in the disk midplane (as defined by sharp changes at icelines of H 2 O, CO 2 and CO) evolves over time, and cannot be assumed fixed, with the C/O ratio in the gas even becoming smaller than the C/O ratio in the ice. In addition, at lower temperatures (< 29 K), gaseous CO colliding with the grains gets converted into CO 2 and other more complex ices, lowering the CO gas abundance between the O 2 and CO thermal icelines. This effect can mimic a CO iceline at a higher temperature than suggested by its binding energy. Conclusions. Chemistry in the disk midplane is ionisation-driven, and evolves over time. This affects which molecules go into forming planets and their atmospheres. In order to reliably predict the atmospheric compositions of forming planets, as well as to relate observed atmospheric C/O ratios of exoplanets to where and how the atmospheres have formed in a disk midplane, chemical evolution needs to be considered and implemented into planet formation models.

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“…While a number of studies have treated the transport of gas and solids separately (e.g. in the context of CO sequestration in disc mid-planes; Piso et al 2015Piso et al , 2016Bergin et al 2016;Kama et al 2016;Booth et al 2017;Krijt et al 2018; or the destruction of carbon grains in the terrestrial planetforming region; Klarmann et al 2018), to our knowledge this is the first study to treat gas and dust transport independently and gas-phase kinetics in detail. We emphasise that differences in the transport of gas and dust is the only way that the bulk atomic abundances (i.e.…”

Section: Introductionmentioning

confidence: 99%

Planet-forming material in a protoplanetary disc: the interplay between chemical evolution and pebble drift

Booth

Ilee

2019

Monthly Notices of the Royal Astronomical Society

100

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The composition of gas and solids in protoplanetary discs sets the composition of planets that form out of them. Recent chemical models have shown that the composition of gas and dust in discs evolves on Myr time-scales, with volatile species disappearing from the gas phase. However, discs evolve due to gas accretion and radial drift of dust on time-scales similar to these chemical time-scales. Here we present the first model coupling the chemical evolution in the disc mid-planes with the evolution of discs due to accretion and radial drift of dust. Our models show that transport will always overcome the depletion of CO 2 from the gas phase, and can also overcome the depletion of CO and CH 4 unless both transport is slow (viscous α 10 −3 ) and the ionization rate is high (ζ ≈ 10 −17 ). Including radial drift further enhances the abundances of volatile species because they are carried in on the surface of grains before evaporating left at their ice lines. Due to large differences in the abundances within 10 au for models with and without efficient radial drift, we argue that composition can be used to constrain models of planet formation via pebble accretion.

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The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks

Cited by 93 publications

References 55 publications

High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes

Planet-forming material in a protoplanetary disc: the interplay between chemical evolution and pebble drift

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