Hydrodynamic Processes in Massive Stars

AbstractThe hydrodynamic processes operating within stellar interiors are far richer than represented by the best stellar evolution model available. Although it is now widely understood, through astrophysical simulation and relevant terrestrial experiment, that many of the basic assumptions which underlie our treatments of stellar evolution are flawed, we lack a suitable, comprehensive replacement. This is due to a deficiency in our fundamental understanding of the transport and mixing properties of a turbulent, reactive, magnetized plasma; a deficiency in knowledge which stems from the richness and variety of solutions which characterize the inherently non-linear set of governing equations. The exponential increase in availability of computing resources, however, is ushering in a new era of understanding complex hydrodynamic flows; and although this field is still in its formative stages, the sophistication already achieved is leading to a dramatic paradigm shift in how we model astrophysical fluid dynamics. We highlight here some recent results from a series of multi-dimensional stellar interior calculations which are part of a program designed to improve our one-dimensional treatment of massive star evolution and stellar evolution in general.

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Massive Star Modeling and Nucleosynthesis

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.617765 ◽

2021 ◽

Vol 8 ◽

Author(s):

Sylvia Ekström

Keyword(s):

Mass Loss ◽

Stellar Evolution ◽

Massive Star ◽

Nuclear Reactions ◽

Massive Stars ◽

Reaction Rates ◽

Star Evolution ◽

Structural Impact ◽

Massive Star Evolution ◽

The Impact

After a brief introduction to stellar modeling, the main lines of massive star evolution are reviewed, with a focus on the nuclear reactions from which the star gets the needed energy to counterbalance its gravity. The different burning phases are described, as well as the structural impact they have on the star. Some general effects on stellar evolution of uncertainties in the reaction rates are presented, with more precise examples taken from the uncertainties of the 12C(α, γ)16O reaction and the sensitivity of the s-process on many rates. The changes in the evolution of massive stars brought by low or zero metallicity are reviewed. The impact of convection, rotation, mass loss, and binarity on massive star evolution is reviewed, with a focus on the effect they have on the global nucleosynthetic products of the stars.

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Massive star evolution: feedbacks in low-Z environment

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007238 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 153-160

Author(s):

Sylvia Ekström ◽

Georges Meynet ◽

Cyril Georgy ◽

José Groh ◽

Arthur Choplin ◽

...

Keyword(s):

Chemical Evolution ◽

Stellar Evolution ◽

Massive Star ◽

Dwarf Galaxies ◽

Massive Stars ◽

Star Evolution ◽

Massive Star Evolution

AbstractMassive stars are the drivers of the chemical evolution of dwarf galaxies. We review here the basics of massive star evolution and the specificities of stellar evolution in low-Z environment. We discuss nucleosynthetic aspects and what observations could constrain our view on the first generations of stars.

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Massive star evolution revealed in the Mass-Luminosity plane

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319001170 ◽

2018 ◽

Vol 14 (S346) ◽

pp. 480-485

Author(s):

Erin R. Higgins ◽

Jorick S. Vink

Keyword(s):

Mass Loss ◽

Stellar Evolution ◽

Massive Star ◽

Main Sequence ◽

Theoretical Models ◽

Physical Processes ◽

Single Star ◽

Star Evolution ◽

Novel Method ◽

Massive Star Evolution

AbstractMassive star evolution is dominated by key physical processes such as mass loss, convection and rotation, yet these effects are poorly constrained, even on the main sequence. We utilise a detached, eclipsing binary HD166734 as a testbed for single star evolution to calibrate new MESA stellar evolution grids. We introduce a novel method of comparing theoretical models with observations in the ‘Mass-Luminosity Plane’, as an equivalent to the HRD (see Higgins & Vink 2018). We reproduce stellar parameters and abundances of HD166734 with enhanced overshooting (αov=0.5), mass loss and rotational mixing. When comparing the constraints of our testbed to the systematic grid of models we find that a higher value of αov=0.5 (rather than αov=0.1) results in a solution which is more likely to evolve to a neutron star than a black hole, due to a lower value of the compactness parameter.

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Massive star evolution in nearby galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900031028 ◽

1984 ◽

Vol 105 ◽

pp. 279-297 ◽

Cited By ~ 2

Author(s):

Roberta M. Humphreys

Keyword(s):

Observational Data ◽

Stellar Evolution ◽

Massive Star ◽

Stellar Content ◽

Individual Stars ◽

Star Evolution ◽

Different Types ◽

Nearby Galaxies ◽

Massive Star Evolution

In this review I will primarily be discussing the observational data relevant to understanding the process of stellar evolution in galaxies of different types. This discussion will focus on the stellar content of the nearer galaxies; those galaxies in which the brightest individual stars are resolved and can be observed.

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Massive star evolution: rotation, winds, and overshooting vectors in the mass-luminosity plane

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834123 ◽

2019 ◽

Vol 622 ◽

pp. A50 ◽

Cited By ~ 10

Author(s):

Erin R. Higgins ◽

Jorick S. Vink

Keyword(s):

Binary System ◽

Mass Loss ◽

Stellar Evolution ◽

Massive Star ◽

Main Sequence ◽

Test Bed ◽

Star Evolution ◽

Red Supergiants ◽

Nitrogen Abundance ◽

Massive Star Evolution

Context. Massive star evolution is dominated by various physical effects, including mass loss, overshooting, and rotation, but the prescriptions of their effects are poorly constrained and even affect our understanding of the main sequence. Aims. We aim to constrain massive star evolution models using the unique test-bed eclipsing binary HD 166734 with new grids of MESA stellar evolution models, adopting calibrated prescriptions of overshooting, mass loss, and rotation. Methods. We introduce a novel tool, called the mass-luminosity plane or M−L plane, as an equivalent to the traditional HR diagram, utilising it to reproduce the test-bed binary HD 166734 with newly calibrated MESA stellar evolution models for single stars. Results. We can only reproduce the Galactic binary system with an enhanced amount of core overshooting (αov = 0.5), mass loss, and rotational mixing. We can utilise the gradient in the M−L plane to constrain the amount of mass loss to 0.5–1.5 times the standard prescription test-bed, and we can exclude extreme reduction or multiplication factors. The extent of the vectors in the M−L plane leads us to conclude that the amount of core overshooting is larger than is normally adopted in contemporary massive star evolution models. We furthermore conclude that rotational mixing is mandatory to obtain the correct nitrogen abundance ratios between the primary and secondary components (3:1) in our test-bed binary system. Conclusions. Our calibrated grid of models, alongside our new M−L plane approach, present the possibility of a widened main sequence due to an increased demand for core overshooting. The increased amount of core overshooting is not only needed to explain the extended main sequence, but the enhanced overshooting is also needed to explain the location of the upper-luminosity limit of the red supergiants. Finally, the increased amount of core overshooting has – via the compactness parameter – implications for supernova explodability.

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Massive star evolution in the Small Magellanic Cloud

Symposium - International Astronomical Union ◽

10.1017/s0074180900212370 ◽

2003 ◽

Vol 212 ◽

pp. 308-315 ◽

Cited By ~ 2

Author(s):

Daniel J. Lennon

Keyword(s):

Stellar Evolution ◽

Massive Star ◽

Main Sequence ◽

Single Star ◽

Promising Alternative ◽

Star Models ◽

Abundance Patterns ◽

Star Evolution ◽

Type Giant ◽

Massive Star Evolution

We discuss abundances for eight early B-type giant/supergiant stars in the SMC cluster NGC 330. All are nitrogen rich with an abundance approximately 1.3 dex higher than an SMC main-sequence field. Given the number of B-type stars with low rotational projected velocities in NGC 330 (all our targets have v sin i < 50 kms–1), we suggest that it is unlikely that the stars in our sample are seen almost pole-on, but rather that they are intrinsically slow rotators. Comparing these results with the predictions of stellar evolution models including the effects of rotationally induced mixing, we conclude that while the abundance patterns may indeed be reproduced, those models with initially large rotational velocities do not reproduce the observed range of effective temperatures of our sample, nor the currently observed rotational velocities. Binary models may be able to produce stars in the observed temperature range and provide a promising alternative to single star models for explaining the observations. We also discuss the clear need for stellar evolution calculations employing the correct chemical mix of carbon, nitrogen and oxygen for the SMC.

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Bridging the gap: from massive stars to supernovae

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2017.0025 ◽

2017 ◽

Vol 375 (2105) ◽

pp. 20170025 ◽

Cited By ~ 2

Author(s):

Justyn R. Maund ◽

Paul A. Crowther ◽

Hans-Thomas Janka ◽

Norbert Langer

Keyword(s):

Stellar Evolution ◽

Observational Studies ◽

Massive Star ◽

Massive Stars ◽

Scientific Meeting ◽

The Other ◽

Star Evolution ◽

Massive Star Evolution ◽

The Universe ◽

Key Questions

Almost since the beginning, massive stars and their resultant supernovae have played a crucial role in the Universe. These objects produce tremendous amounts of energy and new, heavy elements that enrich galaxies, encourage new stars to form and sculpt the shapes of galaxies that we see today. The end of millions of years of massive star evolution and the beginning of hundreds or thousands of years of supernova evolution are separated by a matter of a few seconds, in which some of the most extreme physics found in the Universe causes the explosive and terminal disruption of the star. Key questions remain unanswered in both the studies of how massive stars evolve and the behaviour of supernovae, and it appears the solutions may not lie on just one side of the explosion or the other or in just the domain of the stellar evolution or the supernova astrophysics communities. The need to view massive star evolution and supernovae as continuous phases in a single narrative motivated the Theo Murphy international scientific meeting ‘Bridging the gap: from massive stars to supernovae’ at Chicheley Hall, UK, in June 2016, with the specific purpose of simultaneously addressing the scientific connections between theoretical and observational studies of massive stars and their supernovae, through engaging astronomers from both communities. This article is part of the themed issue ‘Bridging the gap: from massive stars to supernovae’.

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Outflowing Envelopes From Stars at Arbitrary Optical Depths a New Approach to the Problem

Highlights of Astronomy ◽

10.1017/s1539299600021316 ◽

1998 ◽

Vol 11 (1) ◽

pp. 381-381

Author(s):

A.V. Dorodnitsyn

Keyword(s):

Differential Equations ◽

Massive Star ◽

System Of Differential Equations ◽

Continuous Transition ◽

Satisfactory Description ◽

Sonic Point ◽

New Approach ◽

Star Evolution ◽

Matter Flux ◽

Massive Star Evolution

We have considered a stationary outflowing envelope accelerated by the radiative force in arbitrary optical depth case. Introduced approximations provide satisfactory description of the behavior of the matter flux with partially separated radiation at arbitrary optical depths. The obtained systemof differential equations provides a continuous transition of the solution between optically thin and optically thick regions. We analytically derivedapproximate representation of the solution at the vicinity of the sonic point. Using this representation we numerically integrate the system of equations from the critical point to the infinity. Matching the boundary conditions we obtain solutions describing the problem system of differential equations. The theoretical approach advanced in this work could be useful for self-consistent simulations of massive star evolution with mass loss.

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