Stellar physics and evolution calculations enable a broad range of research in astrophysics. Modules for Experiments in Stellar Astrophysics (MESA) is a suite of open source, robust, efficient, thread-safe libraries for a wide range of applications in computational stellar astrophysics. A one-dimensional stellar evolution module, MESAstar, combines many of the numerical and physics modules for simulations of a wide range of stellar evolution scenarios ranging from very low mass to massive stars, including advanced evolutionary phases. MESAstar solves the fully coupled structure and composition equations simultaneously. It uses adaptive mesh refinement and sophisticated timestep controls, and supports shared memory parallelism based on OpenMP. State-of-the-art modules provide equation of state, opacity, nuclear reaction rates, element diffusion data, and atmosphere boundary conditions. Each module is constructed as a separate Fortran 95 library with its own explicitly defined public interface to facilitate independent development. Several detailed examples indicate the extensive verification and testing that is continuously performed and demonstrate the wide range of capabilities that MESA possesses. These examples include evolutionary tracks of very low mass stars, brown dwarfs, and gas giant planets to very old ages; the complete evolutionary track of a 1 M ☉ star from the pre-main sequence (PMS) to a cooling white dwarf; the solar sound speed profile; the evolution of intermediate-mass stars through the He-core burning phase and thermal pulses on the He-shell burning asymptotic giant branch phase; the interior structure of slowly pulsating B Stars and Beta Cepheids; the complete evolutionary tracks of massive stars from the PMS to the onset of core collapse; mass transfer from stars undergoing Roche lobe overflow; and the evolution of helium accretion onto a neutron star. MESA can be downloaded from the project Web site (http://mesa.sourceforge.net/).

https://iopscience.iop.org/article/10.1088/0067-0049/192/1/3/pdf

Modules for Experiments in Stellar Astrophysics (MESA)

We substantially update the capabilities of the open-source software instrument Modules for Experiments in Stellar Astrophysics (MESA). MESA can now simultaneously evolve an interacting pair of differentially rotating stars undergoing transfer and loss of mass and angular momentum, greatly enhancing the prior ability to model binary evolution. New MESA capabilities in fully coupled calculation of nuclear networks with hundreds of isotopes now allow MESA to accurately simulate advanced burning stages needed to construct supernova progenitor models. Implicit hydrodynamics with shocks can now be treated with MESA, enabling modeling of the entire massive star lifecycle, from pre-main sequence evolution to the onset of core collapse and nucleosynthesis from the resulting explosion. Coupling of the GYRE non-adiabatic pulsation instrument with MESA allows for new explorations of the instability strips for massive stars while also accelerating the astrophysical use of asteroseismology data. We improve treatment of mass accretion, giving more accurate and robust near-surface profiles. A new MESA capability to calculate weak reaction rates "on-the-fly" from input nuclear data allows better simulation of accretion induced collapse of massive white dwarfs and the fate of some massive stars. We discuss the ongoing challenge of chemical diffusion in the strongly coupled plasma regime, and exhibit improvements in MESA that now allow for the simulation of radiative levitation of heavy elements in hot stars. We close by noting that the MESA software infrastructure provides bit-for-bit consistency for all results across all the supported platforms, a profound enabling capability for accelerating MESA's development.

https://iopscience.iop.org/article/10.1088/0067-0049/220/1/15/pdf

Modules for experiments in stellar astrophysics (mesa): binaries, pulsations, and explosions

Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions

This is the first of a series of papers presenting the Modules for Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST) project, a new comprehensive set of stellar evolutionary tracks and isochrones computed using MESA, a state-of-the-art open-source 1D stellar evolution package. In this work, we present models with solar-scaled abundance ratios covering a wide range of ages ($5 \leq \rm \log(Age)\;[yr] \leq 10.3$), masses ($0.1 \leq M/M_{\odot} \leq 300$), and metallicities ($-2.0 \leq \rm [Z/H] \leq 0.5$). The models are self-consistently and continuously evolved from the pre-main sequence to the end of hydrogen burning, the white dwarf cooling sequence, or the end of carbon burning, depending on the initial mass. We also provide a grid of models evolved from the pre-main sequence to the end of core helium burning for $-4.0 \leq \rm [Z/H] < -2.0$. We showcase extensive comparisons with observational constraints as well as with some of the most widely used existing models in the literature. The evolutionary tracks and isochrones can be downloaded from the project website at this http URL

https://iopscience.iop.org/article/10.3847/0004-637X/823/2/102/pdf

Mesa isochrones and stellar tracks (mist). i. solar-scaled models

Systems and methods are provided for receiving speech and non-speech communications of natural language questions and/or commands, transcribing the speech and non-speech communications to textual messages, and executing the questions and/or commands. The invention applies context, prior information, domain knowledge, and user specific profile data to achieve a natural environment for one or more users presenting questions or commands across multiple domains. The systems and methods creates, stores and uses extensive personal profile information for each user, thereby improving the reliability of determining the context of the speech and non-speech communications and presenting the expected results for a particular question or command.

Systems and methods for responding to natural language speech utterance

On presente une methode approximee de calcul des coefficients de diffusion pour des plasmas denses caracteristiques des enveloppes de naines blanches

Diffusion coefficients for stellar plasmas

On presente de nouvelles estimations des echelles de temps de diffusion des elements lourds dans les naines blanches

Diffusion in white dwarfs - New results and comparative study

On presente des calculs montrant que la diffusion du carbone a partir du cœur peut contaminer les atmospheres de naines blanches riches en He se refroidissant

Carbon pollution in helium-rich white dwarf atmospheres: time-dependent calculations of the dredge-up process

Time-dependent simulations of episodic accretion of metals onto cool white dwarfs are presented. Calculations are made for Mg, Si, Ca, and Fe in H-rich and He-rich white dwarf models having a mass of 0.6 M ○ . in the range 25,000 K≥T eff ≥5000 K. It is first shown that under the assumption of continuous accretion the metal distributions rapidly reach a steady state in the outer layers of the models. The surface steady-state abundance of a metal directly scales on the assumed accretion rate. Using estimates of accretion rates based on a simplified understanding of the interstellar medium, a two-phase accretion model is next developed

A Study of Metal Abundance Patterns in Cool White Dwarfs. II. Simulations of Accretion Episodes

As a first step toward understanding the presence of traces of metals in a minority of cool white dwarfs, the settling of Mg, Si, Ca, and Fe in models of these stars is investigated in detail. Powerful numerical tools based on finite-element techniques are used to study the evolution of the abundance distribution of a given metal over 25 orders of magnitude

C. Pelletier

Papers

Diffusion coefficients for stellar plasmas

Diffusion in white dwarfs - New results and comparative study

Carbon pollution in helium-rich white dwarf atmospheres: time-dependent calculations of the dredge-up process

A Study of Metal Abundance Patterns in Cool White Dwarfs. II. Simulations of Accretion Episodes

A study of metal abundance patterns in cool white dwarfs. I: Time-dependent calculations of gravitational settling