Chemical Signatures of the FU Ori Outbursts

Molyarova, Tamara; Akimkin, V. V.; Semenov, D.; Ábrahám, P.; Henning, Thomas; Kóspál, Á.; Vorobyov, Eduard I.; Wiebe, D. S.

doi:10.3847/1538-4357/aadfd9

Cited by 43 publications

(40 citation statements)

References 57 publications

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“…Accretion bursts affect the physical characteristics and chemical composition of young protostars, causing peculiar excursions on the Hertzsprung-Russel diagram and changing their lithium abundance (Elbakyan et al 2019;Baraffe et al 2017). In addition, luminosity bursts raise the disk temperature, thus affecting its dynamics and chemical composition (Stamatellos et al 2011;Molyarova et al 2018). Finally, we note the accretion bursts in the ξ = 5% model, though being quite intense and numerous, do not make up for the quiescent accretion and the final stellar mass in this model is notably lower than that of the ξ = 95% model without the bursts.…”

Section: Protostellar Accretionmentioning

confidence: 99%

“…The ξ = 5% model shows a highly variable accretion with episodic bursts in the early stages of evolution, while the ξ = 95% model is characterized by slowly-varying accretion but systematically higher accretion and stellar luminosity. These qualitative differences in the character of accretion and luminosity between models with different rates of mass transport through the CSC are expected to have important repercussions for the chemical evolution of protoplanetary disks (e.g., Molyarova et al 2018).…”

Section: Lower Prestellar-core-mass Modelsmentioning

confidence: 99%

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Gravitoviscous protoplanetary disks with a dust component

Vorobyov

Elbakyan

2019

A&A

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Aims. The central region of a circumstellar disk is difficult to resolve in global numerical simulations of collapsing cloud cores, but its effect on the evolution of the entire disk can be significant. Methods. We use numerical hydrodynamics simulations to model the long-term evolution of self-gravitating and viscous circumstellar disks in the thin-disk limit. Simulations start from the gravitational collapse of prestellar cores of 0.5-1.0 M and both gaseous and dusty subsystems were considered, including a model for dust growth. The inner unresolved 1.0 au of the disk is replaced with a central "smart" cell (CSC) -a simplified model that simulates physical processes that may occur in this region. Results. We found that the mass transport rate through the CSC has an appreciable effect on the evolution of the entire disk. Models with slow mass transport form more massive and warmer disks and they are more susceptible to gravitational instability and fragmentation, including a newly identified episodic mode of disk fragmentation in the T Tauri phase of disk evolution. Models with slow mass transport through the CSC feature episodic accretion and luminosity bursts in the early evolution, while models with fast transport are characterized by a steadily declining accretion rate with low-amplitude flickering. Dust grows to a larger, decimeter size in the slow transport models and efficiently drifts in the CSC, where it accumulates reaching the limit when streaming instability becomes operational. We argue that gravitational instability, together with streaming instability likely operating in the inner disk regions, constitute two concurrent planet-forming mechanisms, which may explain the observed diversity of exoplanetary orbits. Conclusions. We conclude that sophisticated models of the inner unresolved disk regions should be used when modeling the formation and evolution of gaseous and dusty protoplanetary disks.

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Section: Protostellar Accretionmentioning

confidence: 99%

Section: Lower Prestellar-core-mass Modelsmentioning

confidence: 99%

Gravitoviscous protoplanetary disks with a dust component

Vorobyov

Elbakyan

2019

A&A

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“…The recent version of the ANDES 2D code is based on a fully 2D approach and it simultaneously iterates the vertical disk structure and the chemical evolution, which allows one to accurately simulate some time-dependent effects such as luminosity outbursts in the FU Ori-type systems (Molyarova et al 2017(Molyarova et al , 2018. However, this recent version does not feature the detailed gas thermal balance.…”

Section: Thermo-chemical Modelingmentioning

confidence: 99%

“…The ring-like appearance of N 2 D + and DCO + emission in disks is mainly due to low-temperature deuterium fractionation when gaseous CO freezes out in the disk midplane (Qi et al 2013;Ceccarelli et al 2014;Huang & Öberg 2015;Salinas et al 2018;Garufi et al 2020). In addition, temporal variations in physical conditions can also affect chemical abundances, for example, via X-ray flares or episodic accretion outbursts (e.g., Cleeves et al 2017;Molyarova et al 2018;Lee et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Using HCO⁺ isotopologues as tracers of gas depletion in protoplanetary disk gaps

Smirnov-Pinchukov

Semenov

Akimkin

et al. 2020

A&A

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Context. The widespread rings and gaps seen in the dust continuum in protoplanetary disks are sometimes accompanied by similar substructures seen in molecular line emission. One example is the outer gap at ~100 au in AS 209, which shows that the H13CO+ and C18O emission intensities decrease along with the continuum in the gap, while the DCO+ emission increases inside the gap. Aims. We aim to study the behavior of DCO+/H13CO+ and DCO+/HCO+ ratios in protoplanetary disk gaps assuming the two scenarios: (A) the gas depletion follows the dust depletion and (B) only the dust is depleted. Methods. We first modeled the physical disk structure using the thermo-chemical model ANDES. This 1+1D steady-state disk model calculates the thermal balance of gas and dust and includes the far ultraviolet, X-rays, cosmic rays, and other ionization sources together with the reduced chemical network for molecular coolants. Afterward, this physical structure was adopted for calculations of molecular abundances with the extended gas-grain chemical network with deuterium fractionation. Ideal synthetic spectra and 0th-moment maps were produced with the LIne Modeling Engine. Results. We are able to qualitatively reproduce the increase in the DCO+ intensity and the decrease in the H13CO+ and C18O intensities inside the disk gap, which is qualitatively similar to what is observed in the outer AS 209 gap. The corresponding disk model (A) assumes that both the gas and dust are depleted in the gap. The model (B) with the gas-rich gap, where only the dust is depleted, produces emission that is too bright in all HCO+ isotopologues and C18O. Conclusions. The DCO+/H13CO+ line ratio can be used to probe gas depletion in dust continuum gaps outside of the CO snow line. The DCO+/C18O line ratio shows a similar, albeit weaker, effect; however, these species can be observed simultaneously with a single (sub)mm interferometer setup.

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“…This allows us to investigate the sensitivity of the results to the different parameters like grain size distribution, outburst duration, and strength. A spatially resolved chemical modelling is the next necessary step to understand chemical pathways of complex molecules in FU Ori-like vigorous environments (Molyarova et al 2018).…”

Section: Loca-speciesmentioning

confidence: 99%

Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers

Wiebe

Molyarova

Akimkin

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The chemical influence of luminosity outbursts on the environments of young solartype stars is explored. Species are categorised into several types according to their response to the outburst. The first and second types imply chemical changes only during the outburst (with slightly different behaviours). These response types are mostly observed close to the star and are caused by icy mantle evaporation. However, mantles recover after the outburst almost immediately. A notable exception is benzene ice, which is accumulated on dust surfaces during and after the outburst, so that its abundance exceeds the pre-outburst level by orders of magnitude. The third type of response is mostly seen at the disc periphery and implies alteration of abundances during the outburst and preservation of these 'abnormal' abundances for centuries. This behaviour is typical of organic compounds, like HCOOCH 3 , CH 3 CN, CH 2 CO. Their presence in the dark disc regions can be a manifestation of the past outburst. CO and CO 2 only trace past outbursts at the remote disc regions. The outburst changes the C/O ratio, but it quickly returns to the pre-outburst value almost everywhere in the disc. An important factor determining the sensitivity of molecular composition to the outburst is the dust size distribution. The duration of the pre-outburst stage and of the outburst itself influence the chemical effects, if the burst duration is shorter than 50 yr and the duration of the quiescent phase between the bursts is shorter than 100 kyr.

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Chemical Signatures of the FU Ori Outbursts

Cited by 43 publications

References 57 publications

Gravitoviscous protoplanetary disks with a dust component

Gravitoviscous protoplanetary disks with a dust component

Using HCO⁺ isotopologues as tracers of gas depletion in protoplanetary disk gaps

Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers

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Chemical Signatures of the FU Ori Outbursts

Cited by 43 publications

References 57 publications

Gravitoviscous protoplanetary disks with a dust component

Gravitoviscous protoplanetary disks with a dust component

Using HCO+ isotopologues as tracers of gas depletion in protoplanetary disk gaps

Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers

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Using HCO⁺ isotopologues as tracers of gas depletion in protoplanetary disk gaps