Non-LTE radiation hydrodynamics in PLUTO

Colombo, Salvatore; Ibgui, L.; Orlando, S.; Rodríguez, Rafael; Espinosa, G.; González, M.; Stehlé, C.; Peres, G.

doi:10.1051/0004-6361/201935991

Cited by 7 publications

(7 citation statements)

References 77 publications

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“…This must be considered when interpreting the UV excess (see e.g. Calvet & Gullbring 1998;Hartmann et al 2016;Colombo et al 2019). We also expect a pre-heating of the accretion flow as a result of the EUV absorption.…”

Section: Synspec Monochromatic Emergent Intensitymentioning

confidence: 94%

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New insight on accretion shocks onto young stellar objects

Sá

Chièze

Stehlé

et al. 2019

A&A

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Context. Material accreted onto classical T Tauri stars is expected to form a hot quasi-periodic plasma structure that radiates in X-rays. Simulations of this phenomenon only partly match observations. They all rely on a static model for the chromosphere and on the assumption that radiation and matter are decoupled. Aims. We explore the effects of a shock-heated chromosphere and of the coupling between radiation and hydrodynamics on the structure and dynamics of the accretion flow. Methods. We simulated accretion columns that fall onto a stellar chromosphere using the 1D ALE code AstroLabE. This code solves the hydrodynamics equations along with the first two moment equations for radiation transfer, with the help of a dedicated opacity table for the coupling between matter and radiation. We derive the total electron and ion densities from collisional-radiative model. Results. The chromospheric acoustic heating affects the duration of the cycle and the structure of the heated slab. In addition, the coupling between radiation and hydrodynamics leads to a heating of the accretion flow and of the chromosphere: the whole column is pushed up by the inflating chromosphere over several times the steady chromosphere thickness. These last two conclusions are in agreement with the computed monochromatic intensity. Acoustic heating and radiation coupling affect the amplitude and temporal variations of the net X-ray luminosity, which varies between 30 and 94% of the incoming mechanical energy flux, depending on which model is considered.

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Section: Synspec Monochromatic Emergent Intensitymentioning

confidence: 94%

“…However, as previously mentioned, such a study is computationally very demanding and is well beyond the scope of the present paper. Simplified NLTE models, as proposed by Colombo et al (2019), therefore are an interesting starting point in this new direction.…”

Section: Synspec: a Spectrum Synthesisermentioning

confidence: 99%

New insight on accretion shocks onto young stellar objects

Sá

Chièze

Stehlé

et al. 2019

A&A

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“…We have tested the code's ability to reproduce shock waves in optically thick media, in which the dynamical evolution of matter and radiation fields is coupled. We have reproduced the 1D setup considered in Ensman (1994), which is generally used as a standard benchmark in Rad-HD codes (see, e.g., Hayes & Norman 2003;González et al 2007;Commerçon et al 2011;Kolb et al 2013;Colombo et al 2019). In this configuration, both matter and radiation fields are initially uniform in a domain given by the interval [0, 7 × 10 10 ] cm.…”

Section: Radiative Shocksmentioning

confidence: 99%

A Two-moment Radiation Hydrodynamics Scheme Applicable to Simulations of Planet Formation in Circumstellar Disks

Fuksman

Klahr

Flock

et al. 2021

ApJ

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We present a numerical code for radiation hydrodynamics designed as a module for the freely available PLUTO code. We adopt a gray approximation and include radiative transfer following a two-moment approach by imposing the M1 closure to the radiation fields. This closure allows for a description of radiative transport in both the diffusion and free-streaming limits, and is able to describe highly anisotropic radiation transport as can be expected in the vicinity of an accreting planet in a protoplanetary disk. To reduce the computational cost caused by the timescale disparity between radiation and matter fields, we integrate their evolution equations separately in an operator-split way, using substepping to evolve the radiation equations. We further increase the code's efficiency by adopting the reduced speed of light approximation (RSLA). Our integration scheme for the evolution equations of radiation fields relies on implicit-explicit schemes, in which radiation-matter interaction terms are integrated implicitly while fluxes are integrated via Godunov-type solvers. The module is suitable for general astrophysical computations in one, two, and three dimensions in Cartesian, spherical, and cylindrical coordinates, and can be implemented on rotating frames. We demonstrate the algorithm performance on different numerical benchmarks, paying particular attention to the applicability of the RSLA for computations of physical processes in protoplanetary disks. We show 2D simulations of vertical convection in disks and 3D simulations of gas accretion by planetary cores, which are the first of their kind to be solved with a two-moment approach.

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“…where ρ is the plasma mass density, is the fluid velocity, k R and k P are, respectively, the Rosseland and Planck mean opacities, c the speed of light, F the comoving-frame radiation flux, E the plasma internal energy density, E the comoving-frame radiation energy, k B the Boltzmann constant, T the plasma temperature, µ the mean particle weight (assuming solar abundances), m H the hydrogen mass, λ the flux-limiter (Minerbo 1978), and γ = 5/3 the ratio of specific heats. In a companion paper (Colombo et al 2019a; in the following Paper I), we discuss the assumptions and the limits of these equations. Since we are interested in evaluating the effects of irradiation from the post-shock accreting material on the pre-shock accretion column, we neglect the radiation effects (both radiative losses and absorption of radiation by matter) in the pre-shock chromosphere (i.e., k P = k R = 0 and L = 0 in Eqs.…”

Section: The Radiation Hydrodynamics Modelmentioning

confidence: 99%

Effects of radiation in accretion regions of classical T Tauri stars

Colombo

Ibgui

Orlando

et al. 2019

A&A

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Context. Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns, in which optically thin and thick plasma components coexist. Thus an accurate description of these impacts requires to account for the effects of absorption and emission of radiation. Aims. We study the effects of radiation emerging from shock-heated plasma in impact regions on the structure of the pre-shock downfalling material. We investigate if a significant absorption of radiation occurs and if it leads to a pre-shock heating of the accreting gas. Methods. We developed a radiation hydrodynamics model describing an accretion column impacting onto the surface of a Classical T Tauri Star. The model takes into account the stellar gravity, the thermal conduction, and the effects of both radiative losses and absorption of radiation by matter in the non local thermodynamic equilibrium regime. Results. After the impact, a hot slab of post-shock plasma develops at the base of the accretion column. Part of radiation emerging from the slab is absorbed by the pre-shock accreting material. As a result, the pre-shock accretion column gradually heats up to temperatures of 10 5 K, forming a radiative precursor of the shock. The precursor has a thermal structure with the hottest part at T ≈ 10 5 K, with size comparable to that of the hot slab, above the post-shock region. At larger distances the temperature gradually decreases to T ≈ 10 4 K. Conclusions. Our model predicts that ≈ 70% of radiation emitted by the post-shock plasma is absorbed by the pre-shock accretion column immediately above the slab and re-emitted in the UV band. This may explain why accretion rates derived from UV observations are systematically larger than rates inferred from X-ray observations.

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Non-LTE radiation hydrodynamics in PLUTO

Cited by 7 publications

References 77 publications

New insight on accretion shocks onto young stellar objects

New insight on accretion shocks onto young stellar objects

A Two-moment Radiation Hydrodynamics Scheme Applicable to Simulations of Planet Formation in Circumstellar Disks

Effects of radiation in accretion regions of classical T Tauri stars

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