Challenges in 2D Stellar Modeling

Lovekin, Catherine

doi:10.3389/fspas.2019.00077

Cited by 6 publications

(5 citation statements)

References 115 publications

(175 reference statements)

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“…This has significant implications for the spectroscopic determination of atmospheric parameters, such as the effective temperature and surface gravity, as these parameters are significantly affected by gravity darkening (von Zeipel, 1924;Townsend et al, 2004;Espinosa Lara and Rieutord, 2011). From a more theoretical perspective, the distorted spherical symmetry of rapidly-rotating stars impacts the applicability of using 1D models, and because phenomena associated with rapid rotation, such as rotationally-induced mixing, can significantly influence evolutionary tracks in the HR diagram (Maeder and Meynet, 2000;Maeder, 2009;Lovekin, 2020). Moreover, as discussed in section 2.2.1, the Coriolis force perturbs the pulsation frequencies of a rotating star and consequently also the expected parameter range of instability regions in the HR diagram (Townsend, 2005;Bouabid et al, 2013;Szewczuk and Daszyńska-Daszkiewicz, 2017).…”

Section: Instability Domains Of High-mass Starsmentioning

confidence: 99%

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

Bowman

2020

Front. Astron. Space Sci.

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Massive stars are important metal factories in the Universe. They have short and energetic lives, and many of them inevitably explode as a supernova and become a neutron star or black hole. In turn, the formation, evolution and explosive deaths of massive stars impact the surrounding interstellar medium and shape the evolution of their host galaxies. Yet the chemical and dynamical evolution of a massive star, including the chemical yield of the ultimate supernova and the remnant mass of the compact object, strongly depend on the interior physics of the progenitor star. We currently lack empirically calibrated prescriptions for various physical processes at work within massive stars, but this is now being remedied by asteroseismology. The study of stellar structure and evolution using stellar oscillations-asteroseismology-has undergone a revolution in the last two decades thanks to high-precision time series photometry from space telescopes. In particular, the long-term light curves provided by the MOST, CoRoT, BRITE, Kepler/K2, and TESS missions provided invaluable data sets in terms of photometric precision, duration and frequency resolution to successfully apply asteroseismology to massive stars and probe their interior physics. The observation and subsequent modeling of stellar pulsations in massive stars has revealed key missing ingredients in stellar structure and evolution models of these stars. Thus, asteroseismology has opened a new window into calibrating stellar physics within a highly degenerate part of the Hertzsprung-Russell diagram. In this review, I provide a historical overview of the progress made using ground-based and early space missions, and discuss more recent advances and breakthroughs in our understanding of massive star interiors by means of asteroseismology with modern space telescopes.

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Section: Instability Domains Of High-mass Starsmentioning

confidence: 99%

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

Bowman

2020

Front. Astron. Space Sci.

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“…Because massive stars are in general assumed to have spherical symmetry, the angular momentum transport and removal by winds impacts only the radial differential rotation structure which allows the analysis to be simplified to a 1D calculation. However, this assumption is invalid for very rapidly rotating stars and close binary stars for which 2D and 3D calculations are needed (Gagnier et al 2019;De Marco & Izzard 2017;Lovekin 2020).…”

Section: Introductionmentioning

confidence: 99%

Induced differential rotation and mixing in asynchronous binary stars

Koenigsberger

Moreno

Langer

2021

A&A

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Context. Rotation contributes to internal mixing processes and observed variability in massive stars. A significant number of binary stars are not in strict synchronous rotation, including all eccentric systems. This leads to a tidally induced and time-variable differential rotation structure. Aims. We present a method for exploring the rotation structure of asynchronously rotating binary stars. Methods. The method consists of solving the equations of motion of a 3D grid of volume elements located above the rigidly rotating core of a binary star in the presence of gravitational, centrifugal, Coriolis, gas pressure and viscous forces to obtain the angular velocity as a function of the three spatial coordinates and time. The method is illustrated for a short period massive binary in a circular orbit and in an eccentric orbit. Results. We find that for a fixed set of stellar and orbital parameters, the induced rotation structure and its temporal variability depend on the degree of departure from synchronicity. In eccentric systems, the structure changes over the orbital cycle with maximum amplitudes occurring potentially at orbital phases other than periastron passage. We discuss the possible role of the time-dependent tidal flows in enhancing the mixing efficiency and speculate that, in this context, slowly rotating asynchronous binaries could have more efficient mixing than the analogous more rapidly rotating but tidally locked systems. We find that some observed nitrogen abundances depend on the orbital inclination, which, if real, would imply an inhomogeneous chemical distribution over the stellar surface or that tidally induced spectral line variability, which is strongest near the equator, affects the abundance determinations. Our models predict that, neglecting other angular momentum transfer mechanisms, a pronounced initial differential rotation structure converges toward average uniform rotation on the viscous timescale. Conclusions. A broader perspective of binary star structure, evolution and variability can be gleaned by taking into account the processes that are triggered by asynchronous rotation.

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“…We reiterate that the field geometry cannot be directly included in our models, only via the scaling relations. The limitations related to the 1D parametrisation can likely only be resolved once 2D stellar evolution modelling becomes feasible (Espinosa Lara & Rieutord 2011;Lovekin 2020;Reese et al 2021).…”

Section: General Strategymentioning

confidence: 99%

The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities

Keszthelyi

Koter

Götberg

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Magnetic fields can drastically change predictions of evolutionary models of massive stars via mass-loss quenching, magnetic braking, and efficient angular momentum transport, which we aim to quantify in this work. We use the mesa software instrument to compute an extensive main-sequence grid of stellar structure and evolution models, as well as isochrones, accounting for the effects attributed to a surface fossil magnetic field. The grid is densely populated in initial mass (3-60 M⊙), surface equatorial magnetic field strength (0-50 kG), and metallicity (representative of the Solar neighbourhood and the Magellanic Clouds). We use two magnetic braking and two chemical mixing schemes and compare the model predictions for slowly-rotating, nitrogen-enriched (‘Group 2’) stars with observations in the Large Magellanic Cloud. We quantify a range of initial field strengths that allow for producing Group 2 stars and find that typical values (up to a few kG) lead to solutions. Between the subgrids, we find notable departures in surface abundances and evolutionary paths. In our magnetic models, chemical mixing is always less efficient compared to non-magnetic models due to the rapid spin-down. We identify that quasi-chemically homogeneous main sequence evolution by efficient mixing could be prevented by fossil magnetic fields. We recommend comparing this grid of evolutionary models with spectropolarimetric and spectroscopic observations with the goals of i) revisiting the derived stellar parameters of known magnetic stars, and ii) observationally constraining the uncertain magnetic braking and chemical mixing schemes.

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Challenges in 2D Stellar Modeling

Cited by 6 publications

References 115 publications

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

Induced differential rotation and mixing in asynchronous binary stars

The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities

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