Róbert Andrássy
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View article: Magnetically driven outflows in the 3D common envelope evolution of massive stars
Magnetically driven outflows in the 3D common envelope evolution of massive stars Open
Recent three-dimensional magnetohydrodynamical simulations of the common envelope interaction have revealed the self-consistent formation of bipolar magnetically driven outflows. These outflows are launched from a toroidal structure that h…
View article: From spherical stars to disk-like structures: 3D common-envelope evolution of massive binaries beyond inspiral
From spherical stars to disk-like structures: 3D common-envelope evolution of massive binaries beyond inspiral Open
Self-consistent three-dimensional modeling of the entire common-envelope phase of gravitational wave progenitor systems until full envelope ejection is challenged by the vast range of spatial and temporal scales involved in the problem. Pr…
View article: From spherical stars to disk-like structures: 3D common-envelope evolution of massive binaries beyond inspiral
From spherical stars to disk-like structures: 3D common-envelope evolution of massive binaries beyond inspiral Open
Three-dimensional simulations usually fail to cover the entire dynamical common-envelope phase of gravitational wave progenitor systems due to the vast range of spatial and temporal scales involved. We investigated the common-envelope inte…
View article: Large-scale ordered magnetic fields generated in mergers of helium white dwarfs
Large-scale ordered magnetic fields generated in mergers of helium white dwarfs Open
Stellar mergers are one important path to highly magnetised stars. Mergers of two low-mass white dwarfs may create up to every third hot subdwarf star. The merging process is usually assumed to dramatically amplify magnetic fields. However…
View article: Large-scale ordered magnetic fields generated in mergers of helium white dwarfs
Large-scale ordered magnetic fields generated in mergers of helium white dwarfs Open
Stellar mergers are one important path to highly magnetised stars. Mergers of two low-mass white dwarfs may create up to every third hot subdwarf star. The merging process is usually assumed to dramatically amplify magnetic fields. However…
View article: Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows
Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows Open
High-order Godunov methods for gas dynamics have become a standard tool for simulating different classes of astrophysical flows. Their accuracy is mostly determined by the spatial interpolant used to reconstruct the pair of Riemann states …
View article: Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows
Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows Open
Supplementary materials for the paper "Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows". The supplementary materials are split into two .zip archives (KH2D-plots.zip and 3D-TURBULENCE-WA…
View article: Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows
Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows Open
Supplementary materials for the paper "Performance of high-order Godunov-type methods in simulations of astrophysical low Mach number flows". The supplementary materials are split into two .zip archives (KH2D-plots.zip and 3D-TURBULENCE-WA…
View article: Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell
Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell Open
Convection is one of the most important mixing processes in stellar interiors. Hydrodynamic mass entrainment can bring fresh fuel from neighboring stable layers into a convection zone, modifying the structure and evolution of the star. Und…
View article: 3D hydrodynamic simulations of massive main-sequence stars – I. Dynamics and mixing of convection and internal gravity waves
3D hydrodynamic simulations of massive main-sequence stars – I. Dynamics and mixing of convection and internal gravity waves Open
We performed 3D hydrodynamic simulations of the inner $\approx 50{{\ \rm per\ cent}}$ radial extent of a $25\,\,\mathrm{\mathrm{M}_\odot }$ star in the early phase of the main sequence and investigate core convection and internal gravity w…
View article: Supplementary materials for the paper "Towards a self-consistent model of the convective core boundary in upper-main-sequence stars"
Supplementary materials for the paper "Towards a self-consistent model of the convective core boundary in upper-main-sequence stars" Open
Supplementary materials for the paper "Towards a self-consistent model of the convective core boundary in upper-main-sequence stars" (Andrassy et al. 2023). The zip files contain the two MESA models used in the paper (one without and one w…
View article: Supplementary materials for the paper "Towards a self-consistent model of the convective core boundary in upper-main-sequence stars"
Supplementary materials for the paper "Towards a self-consistent model of the convective core boundary in upper-main-sequence stars" Open
Supplementary materials for the paper "Towards a self-consistent model of the convective core boundary in upper-main-sequence stars" (Andrassy et al. 2023). The zip files contain the two MESA models used in the paper (one without and one w…
View article: 3D hydrodynamic simulations of massive main-sequence stars. I. Dynamics and mixing of convection and internal gravity waves
3D hydrodynamic simulations of massive main-sequence stars. I. Dynamics and mixing of convection and internal gravity waves Open
We performed 3D hydrodynamic simulations of the inner $\approx 50\%$ radial extent of a $25\ \mathrm{M_\odot}$ star in the early phase of the main sequence and investigate core convection and internal gravity waves in the core-envelope bou…
View article: A finite-volume scheme for modeling compressible magnetohydrodynamic flows at low Mach numbers in stellar interiors
A finite-volume scheme for modeling compressible magnetohydrodynamic flows at low Mach numbers in stellar interiors Open
Fully compressible magnetohydrodynamic (MHD) simulations are a fundamental tool for investigating the role of dynamo amplification in the generation of magnetic fields in deep convective layers of stars. The flows that arise in such enviro…
View article: Dynamics in a stellar convective layer and at its boundary: Comparison of five 3D hydrodynamics codes
Dynamics in a stellar convective layer and at its boundary: Comparison of five 3D hydrodynamics codes Open
Our ability to predict the structure and evolution of stars is in part limited by complex, 3D hydrodynamic processes such as convective boundary mixing. Hydrodynamic simulations help us understand the dynamics of stellar convection and con…
View article: Well-balanced treatment of gravity in astrophysical fluid dynamics simulations at low Mach numbers
Well-balanced treatment of gravity in astrophysical fluid dynamics simulations at low Mach numbers Open
Context. Accurate simulations of flows in stellar interiors are crucial to improving our understanding of stellar structure and evolution. Because the typically slow flows are merely tiny perturbations on top of a close balance between gra…
View article: Multidimensional low-Mach number time-implicit hydrodynamic simulations of convective helium shell burning in a massive star
Multidimensional low-Mach number time-implicit hydrodynamic simulations of convective helium shell burning in a massive star Open
Context. A realistic parametrization of convection and convective boundary mixing in conventional stellar evolution codes is still the subject of ongoing research. To improve the current situation, multidimensional hydrodynamic simulations…
View article: 3D1D hydro-nucleosynthesis simulations – I. Advective–reactive post-processing method and its application to H ingestion into He-shell flash convection in rapidly accreting white dwarfs
3D1D hydro-nucleosynthesis simulations – I. Advective–reactive post-processing method and its application to H ingestion into He-shell flash convection in rapidly accreting white dwarfs Open
We present two mixing models for post-processing of 3D hydrodynamic simulations applied to convective–reactive i-process nucleosynthesis in a rapidly accreting white dwarf (RAWD) with [Fe/H] = −2.6, in which H is ingested into a convective…
View article: 3D hydrodynamic simulations of C ingestion into a convective O shell
3D hydrodynamic simulations of C ingestion into a convective O shell Open
Interactions between convective shells in evolved massive stars have been linked to supernova impostors, to the production of the odd-Z elements Cl, K, and Sc, and they might also help generate the large-scale asphericities that are known …
The i-process yields of rapidly accreting white dwarfs from multicycle He-shell flash stellar evolution models with mixing parametrizations from 3D hydrodynamics simulations Open
We have modelled the multicycle evolution of rapidly accreting CO white dwarfs (RAWDs) with stable H burning intermittent with strong He-shell flashes on their surfaces for 0.7 ≤ MRAWD/M⊙ ≤ 0.75 and [Fe/H] ranging from 0 to −2.6. We have a…
View article: Simulating 3-D Stellar Hydrodynamics using PPM and PPB Multifluid Gas Dynamics on CPU and CPU+GPU Nodes
Simulating 3-D Stellar Hydrodynamics using PPM and PPB Multifluid Gas Dynamics on CPU and CPU+GPU Nodes Open
The special computational challenges of simulating 3-D hydrodynamics in deep stellar interiors are discussed, and numerical algorithmic responses described. Results of recent simulations carried out at scale on the NSF’s Blue Waters machin…
View article: 3D Nucleosynthesis in Convective Environments
3D Nucleosynthesis in Convective Environments Open
Poster displayed at Chemical Evolution and Nucleosynthesis Across the Galaxy (CENEG) 2018.
View article: Convective–reactive nucleosynthesis of K, Sc, Cl and p-process isotopes in O–C shell mergers
Convective–reactive nucleosynthesis of K, Sc, Cl and p-process isotopes in O–C shell mergers Open
We address the deficiency of odd-Z elements P, Cl, K and Sc in Galactic chemical evolution models through an investigation of the nucleosynthesis of interacting convective O and C shells in massive stars. 3D hydrodynamic simulations of O-s…
View article: Posters also presented at the Symposium
Posters also presented at the Symposium Open
I am reporting on our team's progress in investigating fundamental properties of convective shells in the deep stellar interior during advanced stages of stellar evolution. We have performed a series of 3D hydrodynamic simulations of conve…
View article: Idealized hydrodynamic simulations of turbulent oxygen-burning shell convection in 4π geometry
Idealized hydrodynamic simulations of turbulent oxygen-burning shell convection in 4π geometry Open
This work investigates the properties of convection in stars with particular\nemphasis on entrainment across the upper convective boundary (CB). Idealised\nsimulations of turbulent convection in the O-burning shell of a massive star\nare p…
View article: Convective settling in main sequence stars: Li and Be depletion
Convective settling in main sequence stars: Li and Be depletion Open
The process of convective settling is based on the assumption that a small fraction of the low-entropy downflows sink from the photosphere down to the bottom of the star’s envelope convection zone retaining a substantial entropy contrast. …
View article: Overshooting by differential heating
Overshooting by differential heating Open
\n On the long nuclear time scale of stellar main-sequence evolution, even weak mixing processes can become relevant for redistributing chemical species in a star. We investigate a process of “differential heating”, which occurs when a tem…
View article: Convective overshooting in stars
Convective overshooting in stars Open
Numerous observations provide evidence that the standard picture, in which convective mixing is limited to the unstable layers of a star, is incomplete. The mixing layers in real stars are significantly more extended than what the standard…