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Galaxies
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The Structure and Evolution of Stars
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The Structure and Evolution of Stars

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 12787

Special Issue Editors

Prof. Dr. Jorick S. Vink

E-Mail Website
Guest Editor
Armagh Observatory and Plantearium, Armagh BT65 9DG, UK
Interests: massive stars; stellar evolution; model atmospheres; stellar winds; Herbig Ae/Be stars; T Tauri stars
Special Issues, Collections and Topics in MDPI journals
Dr. Dominic Bowman

E-Mail Website
Guest Editor
Institute of Astronomy, KU Leuven, Leuven, Belgium
Interests: massive stars; asteroseismology; stellar evolution
Dr. Jennifer Van Saders

E-Mail Website
Guest Editor
IfA, University of Hawaii, Honolulu, HI, USA
Interests: structure and evolution of stars; stellar rotation; stellar age diagnostics; asteroseismology

Special Issue Information

Dear Colleagues,

Accurate stellar evolution modelling is only possible once the correct stellar structures have been constructed. While many papers and books on stellar evolution have been published over the decades, we feel a comprehensive volume describing the physics and state of the art of stellar structures over the stellar mass range is missing.

Stars of different masses and ages have different internal structures. The differences in these structures result in different luminosities, classifications and evolutions. The development of asteroseismology has given us a deeper understanding of the internal structures of stars. In addition, the study of physics such as nuclear reactions and chemicals and angular momentum transport inside stars helps us understand the basic physical properties of stars across the HR diagram.

This topic will focus on the internal structure of stars, especially on the main sequence, which will help understand the evolution of all stages from birth to death as white dwarfs, neutron stars and black holes.

References:

Aerts, 2021, RiMP 93, Issue 1, article id.015001

Bowman, 2020, Fron. Astron. Space Sci. 7, id.70

Graefener et al., 2012, A&A 538, 40

Jiang et al., 2015, ApJ 813, 74

Johnston, 2022, A&A 655, A29

Prof. Dr. Jorick Sandor Vink
Dr. Dominic Bowman
Dr. Jennifer Van Saders
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • stellar structure
  • stellar evolution
  • convection
  • diffusion
  • magnetic fields
  • mixing-length theory
  • convective boundaries
  • overshooting
  • asteroseismology
  • massive stars
  • radiation pressure

Published Papers (7 papers)

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Review

24 pages, 1727 KiB  
Review
Three Dimensional Natures of Massive Star Envelopes
by Yan-Fei Jiang
Galaxies 2023, 11(5), 105; https://doi.org/10.3390/galaxies11050105 - 11 Oct 2023
Cited by 2 | Viewed by 1207
Abstract
In this paper, we review our current understanding of the outer envelope structures of massive stars based on three-dimensional (3D) radiation hydrodynamic simulations. We briefly summarize the fundamental issues in constructing hydrostatic one-dimensional (1D) stellar evolution models when stellar luminosity approaches the Eddington [...] Read more.
In this paper, we review our current understanding of the outer envelope structures of massive stars based on three-dimensional (3D) radiation hydrodynamic simulations. We briefly summarize the fundamental issues in constructing hydrostatic one-dimensional (1D) stellar evolution models when stellar luminosity approaches the Eddington value. Radiation hydrodynamic simulations in 3D covering the mass range from 13M⊙ to 80M⊙ always find a dynamic envelope structure with the time-averaged radial profiles matching 1D models with an adjusted mixing-length parameter when convection is subsonic. Supersonic turbulence and episodic mass loss are generally found in 3D models when stellar luminosity is super-Eddington locally due to the opacity peaks and convection being inefficient. Turbulent pressure plays an important role in supporting the outer envelope, which makes the photosphere more extended than predictions from 1D models. Massive star lightcurves are always found to vary with a characteristic timescale consistent with the thermal time scale at the location of the iron opacity peak. The amplitude of the variability as well as the power spectrum can explain the commonly observed stochastic low-frequency variability of mass stars observed by TESS over a wide range of parameters in an HR diagram. The 3D simulations can also explain the ubiquitous macro-turbulence that is needed for spectroscopic fitting in massive stars. Implications of 3D simulations for improving 1D stellar evolution models are also discussed. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
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12 pages, 261 KiB  
Review
The Structure and Evolution of Stars: Introductory Remarks
by Dominic M. Bowman, Jennifer van Saders and Jorick S. Vink
Galaxies 2023, 11(5), 94; https://doi.org/10.3390/galaxies11050094 - 31 Aug 2023
Viewed by 1176
Abstract
In this introductory chapter of the Special Issue entitled ‘The Structure and Evolution of Stars’, we highlight the recent major progress made in our understanding of the physics that governs stellar interiors. In so doing, we combine insight from observations, 1D evolutionary modelling [...] Read more.
In this introductory chapter of the Special Issue entitled ‘The Structure and Evolution of Stars’, we highlight the recent major progress made in our understanding of the physics that governs stellar interiors. In so doing, we combine insight from observations, 1D evolutionary modelling and 2D + 3D rotating (magneto)hydrodynamical simulations. Therefore, a complete and compelling picture of the necessary ingredients in state-of-the-art stellar structure theory and areas in which improvements still need to be made are contextualised. Additionally, the over-arching perspective linking all the themes of subsequent chapters is presented. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
31 pages, 44660 KiB  
Review
Multidimensional Simulations of Core Convection
by Daniel Lecoanet and Philipp V. F. Edelmann
Galaxies 2023, 11(4), 89; https://doi.org/10.3390/galaxies11040089 - 31 Jul 2023
Cited by 4 | Viewed by 1143
Abstract
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 and post-main sequence evolution of these stars. These effects must [...] Read more.
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 and post-main sequence evolution of these stars. These effects must be understood to accurately model the structure and evolution of intermediate- and high-mass stars. Unfortunately, there are many challenges in simulating core convection due to the wide range of temporal and spatial scales, as well as many important physics effects. In this review, we describe the latest numerical strategies to address these challenges. We then describe the latest state-of-the-art simulations of core convection, summarizing their main findings. These simulations have led to important insights into many of the processes associated with core convection. Two outstanding problems with multidimensional simulations are, 1. it is not always straightforward to extrapolate from simulation parameters to the parameters of real stars; and 2. simulations using different methods sometimes appear to arrive at contradictory results. To address these issues, next generation simulations of core convection must address how their results depend on stellar luminosity, dimensionality, and turbulence intensity. Furthermore, code comparison projects will be essential to establish robust parameterizations that will become the new standard in stellar modeling. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
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31 pages, 2008 KiB  
Review
A Review of the Mixing Length Theory of Convection in 1D Stellar Modeling
by Meridith Joyce and Jamie Tayar
Galaxies 2023, 11(3), 75; https://doi.org/10.3390/galaxies11030075 - 16 Jun 2023
Cited by 19 | Viewed by 1744
Abstract
We review the application of the one-dimensional Mixing Length Theory (MLT) model of convection in stellar interiors and low-mass stellar evolution. We summarize the history of MLT, present a derivation of MLT in the context of 1D stellar structure equations, and discuss the [...] Read more.
We review the application of the one-dimensional Mixing Length Theory (MLT) model of convection in stellar interiors and low-mass stellar evolution. We summarize the history of MLT, present a derivation of MLT in the context of 1D stellar structure equations, and discuss the physical regimes in which MLT is relevant. We review attempts to improve and extend the formalism, including to higher dimensions. We discuss the interactions of MLT with other modeling physics, and demonstrate the impact of introducing variations in the convective mixing length, αMLT, on stellar tracks and isochrones. We summarize the process of performing a solar calibration of αMLT and state-of-the-art on calibrations to non-solar targets. We discuss the scientific implications of changing the mixing length, using recent analyses for demonstration. We review the most prominent successes of MLT, and the remaining challenges, and we conclude by speculating on the future of this treatment of convection. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
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20 pages, 2221 KiB  
Review
Opacities and Atomic Diffusion
by Georges Alecian and Morgan Deal
Galaxies 2023, 11(3), 62; https://doi.org/10.3390/galaxies11030062 - 25 Apr 2023
Cited by 1 | Viewed by 1350
Abstract
Opacity is a fundamental quantity for stellar modeling, and it plays an essential role throughout the life of stars. After gravity drives the collapse of interstellar matter into a protostar, the opacity determines how this matter is structured around the stellar core. The [...] Read more.
Opacity is a fundamental quantity for stellar modeling, and it plays an essential role throughout the life of stars. After gravity drives the collapse of interstellar matter into a protostar, the opacity determines how this matter is structured around the stellar core. The opacity explains how the radiation field interacts with the matter and how a major part of the energy flows through the star. It results from all the microscopic interactions of photons with atoms. Part of the momentum exchange between photons and atoms gives rise to radiative accelerations (specific to each type of atom), which are strongly involved in a second-order process: atomic diffusion. Although this process is a slow one, it can have a significant impact on stellar structure and chemical composition measurements. In this review, we discuss the way opacities are presently computed and used in numerical codes. Atomic diffusion is described, and the current status of the consideration of this process is presented. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
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45 pages, 9124 KiB  
Review
Convective Boundary Mixing in Main-Sequence Stars: Theory and Empirical Constraints
by Evan H. Anders and May G. Pedersen
Galaxies 2023, 11(2), 56; https://doi.org/10.3390/galaxies11020056 - 14 Apr 2023
Cited by 16 | Viewed by 2394
Abstract
The convective envelopes of solar-type stars and the convective cores of intermediate- and high-mass stars share boundaries with stable radiative zones. Through a host of processes we collectively refer to as “convective boundary mixing” (CBM), convection can drive efficient mixing in these nominally [...] Read more.
The convective envelopes of solar-type stars and the convective cores of intermediate- and high-mass stars share boundaries with stable radiative zones. Through a host of processes we collectively refer to as “convective boundary mixing” (CBM), convection can drive efficient mixing in these nominally stable regions. In this review, we discuss the current state of CBM research in the context of main-sequence stars through three lenses. (1) We examine the most frequently implemented 1D prescriptions of CBM—exponential overshoot, step overshoot, and convective penetration—and we include a discussion of implementation degeneracies and how to convert between various prescriptions. (2) Next, we examine the literature of CBM from a fluid dynamical perspective, with a focus on three distinct processes: convective overshoot, entrainment, and convective penetration. (3) Finally, we discuss observational inferences regarding how much mixing should occur in the cores of intermediate- and high-mass stars as well as the implied constraints that these observations place on 1D CBM implementations. We conclude with a discussion of pathways forward for future studies to place better constraints on this difficult challenge in stellar evolution modeling. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
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26 pages, 5012 KiB  
Review
Magnetism in High-Mass Stars
by Zsolt Keszthelyi
Galaxies 2023, 11(2), 40; https://doi.org/10.3390/galaxies11020040 - 05 Mar 2023
Cited by 8 | Viewed by 2480
Abstract
Magnetism is a ubiquitous property of astrophysical plasmas, yet stellar magnetism still remains far from being completely understood. In this review, we describe recent observational and modelling efforts and progress to expand our knowledge of the magnetic properties of high-mass stars. Several mechanisms [...] Read more.
Magnetism is a ubiquitous property of astrophysical plasmas, yet stellar magnetism still remains far from being completely understood. In this review, we describe recent observational and modelling efforts and progress to expand our knowledge of the magnetic properties of high-mass stars. Several mechanisms (magneto-convection, mass-loss quenching, internal angular momentum transport, and magnetic braking) have significant implications for stellar evolution, populations, and end-products. Consequently, it remains an urgent issue to address and resolve open questions related to magnetism in high-mass stars. Full article
(This article belongs to the Special Issue The Structure and Evolution of Stars)
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