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(Abridged) We describe the results of three-dimensional (3D) numerical simulations designed to study turbulent convection in the stellar interiors, and compare them to stellar mixing-length theory (MLT). Simulations in 2D are significantly…

Astrophysics · Physics 2011-02-11 Casey A. Meakin , David Arnett

Within our Galaxy, supernova remnants are believed to be the major sources of cosmic rays up to the "knee". However important questions remain regarding the share of the hadronic and leptonic components, and the fraction of the supernova…

High Energy Astrophysical Phenomena · Physics 2016-09-13 Gilles Ferrand , Samar Safi-Harb

We update the capabilities of the open-knowledge software instrument Modules for Experiments in Stellar Astrophysics (MESA). RSP is a new functionality in MESAstar that models the non-linear radial stellar pulsations that characterize RR…

Turbulent mixing of chemical elements by convection has fundamental effects on the evolution of stars. The standard algorithm at present, mixing-length theory (MLT), is intrinsically local, and must be supplemented by extensions with…

Solar and Stellar Astrophysics · Physics 2017-02-22 W. David Arnett , E. Moravveji

Massive stars are key sources of radiative, kinetic, and chemical feedback in the universe. Grids of massive star models computed by different groups each using their own codes, input physics choices and numerical approximations, however,…

Solar and Stellar Astrophysics · Physics 2015-06-23 Samuel Jones , Raphael Hirschi , Marco Pignatari , Alexander Heger , Cyril Georgy , Nobuya Nishimura , Chris Fryer , Falk Herwig

We are reaching relative maturity and standardization in one-dimensional single-star stellar evolution and pulsation modeling, and are making advances in binary and 2D and 3D models. However, many physical inputs are still uncertain or…

Solar and Stellar Astrophysics · Physics 2014-01-06 Joyce A. Guzik

We show that, for the scalar field cosmology with exponential potential, the set of values of the coupling parameter for which the solutions undergo a transient period of acceleration is much larger than the set discussed in the literature.…

General Relativity and Quantum Cosmology · Physics 2014-01-29 Mustapha Azreg-Aïnou

The cores of main sequence intermediate- and high-mass stars are convective. Mixing at the radiative-convective boundary, waves excited by the convection, and magnetic fields generated by convective dynamos all influence the main sequence…

Solar and Stellar Astrophysics · Physics 2023-08-02 Daniel Lecoanet , Philipp V. F. Edelmann

Both observations and direct numerical simulations are discordant with predictions of conventional stellar evolution codes for the latest stages of a massive star's life prior to core collapse. We suggest that the problem lies in the…

Solar and Stellar Astrophysics · Physics 2014-04-03 Nathan Smith , David Arnett

We perform two-dimensional numerical simulations of core convection for zero-age-main-sequence stars covering a mass range from 3 $M_\odot$ to 20 $M_\odot$. The simulations are performed with the fully compressible time-implicit code MUSIC.…

Solar and Stellar Astrophysics · Physics 2023-01-18 I. Baraffe , J. Clarke , A. Morison , D. G. Vlaykov , T. Constantino , T. Goffrey , T. Guillet , A. Le Saux , J. Pratt

We investigate the hydrodynamics of the core helium flash near its peak. Past research concerned with the dynamics of this event is inconclusive. However, the most recent multidimensional hydrodynamic studies suggest a quiescent behavior…

Astrophysics · Physics 2009-11-13 M. Mocak , E. Mueller , A. Weiss , K. Kifonidis

Context: Internal chemical mixing in intermediate- and high-mass stars represents an immense uncertainty in stellar evolution models.In addition to extending the main-sequence lifetime, chemical mixing also appreciably increases the mass of…

Solar and Stellar Astrophysics · Physics 2021-11-10 Cole Johnston

We investigate simulated turbulent flow within thermally driven stellar convection zones. Different driving sources are studied, including cooling at the top of the convectively unstable region, as occurs in surface convection zones; and…

Solar and Stellar Astrophysics · Physics 2015-05-18 Casey Meakin , David Arnett

The outer envelopes of massive ($M\gtrsim10\,M_{\odot}$) stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and helium) that trigger near-surface convection zones.…

Solar and Stellar Astrophysics · Physics 2023-07-19 William Schultz , Lars Bildsten , Yan-Fei Jiang

The inner structure of core-helium burning (CHeB) stars remains uncertain due to the yet unknown nature of mixing at the boundary of their cores. Large convective cores beyond a bare Schwarzschild model are favoured both from theoretical…

Solar and Stellar Astrophysics · Physics 2023-11-21 Simon Blouin , Falk Herwig , Huaqing Mao , Pavel Denissenkov , Paul R. Woodward

We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESA Star. Improvements in MESA Star's ability to model…

Three regions of excessive flux of cosmic rays with energies of the order of PeV are found in the experimental data of the EAS MSU array at a confidence level greater than 4\sigma. For two of them, there are similar regions in the…

High Energy Astrophysical Phenomena · Physics 2011-12-24 G. V. Kulikov , M. Yu. Zotov

Multi-dimensional fluid flow plays a paramount role in the explosions of massive stars as core-collapse supernovae. In recent years, three-dimensional (3D) simulations of these phenomena have matured significantly. Considerable progress has…

Solar and Stellar Astrophysics · Physics 2020-06-11 B. Müller

The non-local hydrodynamic moment equations for compressible convection are compared to numerical simulations. Convective and radiative flux typically deviate less than 20% from the 3D simulations, while mean thermodynamic quantities are…

Astrophysics · Physics 2009-10-31 F. Kupka

We present 3-D hydrodynamical simulations of core convection with a stably stratified envelope of a \unit{25}{\Msun} star in the early phase of the main-sequence. We use the explicit gas-dynamics code \code{PPMstar} which tracks two fluids…

Solar and Stellar Astrophysics · Physics 2024-08-13 Huaqing Mao , Paul Woodward , Falk Herwig , Pavel A. Denissenkov , Simon Blouin , William Thompson , Benjamin McDermott