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Ultramassive white dwarfs (UMWDs; defined by masses $\gtrsim 1.1\,{\rm M}_\odot$) are prime targets for seismology, because they pass through the ZZ Ceti instability strip at the same time that their cores crystallize. Recent studies…

太阳与恒星天体物理 · 物理学 2025-09-10 Daniel Blatman , Nicholas Z. Rui , Sivan Ginzburg , Jim Fuller

We extend our model of magnetic braking (MB), driven by an $\alpha-\Omega$ dynamo mechanism, from fully convective M-dwarfs (FCMDs) to explain the surface and internal spin $P_\mathrm{spin}$ evolution of partly convective dwarfs (PCDs)…

太阳与恒星天体物理 · 物理学 2024-07-11 Arnab Sarkar , Patrick Eggenberger , Lev Yungelson , Christopher A. Tout

White dwarfs are stellar remnants devoid of a nuclear energy source, gradually cooling over billions of years and eventually freezing into a solid state from the inside out. Recently, it was discovered that a population of freezing white…

太阳与恒星天体物理 · 物理学 2024-09-09 Antoine Bédard , Simon Blouin , Sihao Cheng

Many of the current problems related to the evolution of cataclysmic variables revolve around the magnetic nature of the main sequence secondary. It is known that magnetic fields alter the structure of low mass stars. In particular, they…

太阳与恒星天体物理 · 物理学 2025-07-10 Conor M. Larsen , James MacDonald

Solar-type stars exhibit a rich variety of magnetic activity. Seeking to explore the convective origins of this activity, we have carried out a series of global 3D magnetohydrodynamic (MHD) simulations with the anelastic spherical harmonic…

太阳与恒星天体物理 · 物理学 2015-06-12 Nicholas J. Nelson , Benjamin P. Brown , A. Sacha Brun , Mark S. Miesch , Juri Toomre

The prediction of the spins of the compact remnants is a fundamental goal of the theory of stellar evolution. Here, we confront the predictions for white dwarf spins from evolutionary models including rotation with observational…

天体物理学 · 物理学 2009-11-13 M. P. L. Suijs , N. Langer , A. -J. Poelarends , S. -C. Yoon , A. Heger , F. Herwig

Natural dynamos such as planets and stars generate global scale magnetic field despite the inferred presence of small scale turbulence. Such systems are known as large scale dynamos and are typically driven by convection and influenced by…

流体动力学 · 物理学 2022-02-24 Ming Yan , Michael A. Calkins

Cataclysmic Variables (CV) are close binary systems, in which the primary, the more massive star, is a white dwarf. CVs usually exhibit a number of periodicities, most of which are now understood. However, recently, a new phenomenon was…

天体物理学 · 物理学 2008-11-26 G. Tovmassian , S. Zharikov , V. Neustroev

Once carbon--oxygen white dwarfs cool sufficiently, they crystallize from the inside out. If the white dwarf is rich enough in ${}^{22}\mathrm{Ne}$, these crystallized solids are buoyant and rapidly rise, efficiently liberating potential…

太阳与恒星天体物理 · 物理学 2026-01-05 Nicholas Z. Rui , Jim Fuller

It was predicted more than 40 years ago that the cores of the coolest white dwarf stars should eventually crystallize. This effect is one of the largest sources of uncertainty in white dwarf cooling models, which are now routinely used to…

天体物理学 · 物理学 2009-11-10 T. S. Metcalfe , M. H. Montgomery , A. Kanaan

Core convection and dynamo activity deep within rotating A-type stars of 2 solar masses are studied with 3--D nonlinear simulations. Our modeling considers the inner 30% by radius of such stars, thus capturing within a spherical domain the…

天体物理学 · 物理学 2008-11-26 Allan Sacha Brun , Matthew K. Browning , Juri Toomre

White Dwarfs (WDs) are the final evolutionary product of the vast majority of stars in the Universe. They are electron-degenerate structures characterized by no stable thermonuclear activity, and their evolution is generally described as a…

星系天体物理 · 物理学 2021-09-07 J. Chen , F. R. Ferraro , M. Cadelano , M. Salaris , B. Lanzoni , C. Pallanca , L. G. Althaus , E. Dalessandro , -

The formation channels and predicted populations of double-white dwarfs (DWDs) are important because a subset will evolve to be gravitational-wave sources and/or progenitors of Type Ia supernovae. Given the observed population of…

太阳与恒星天体物理 · 物理学 2020-07-22 E. C. Wilson , J. Nordhaus

We investigate numerically magnetic field generation by thermal convection with square periodicity cells in a rotating horizontal layer of electrically-conducting fluid with stress-free electrically perfectly conducting boundaries for…

混沌动力学 · 物理学 2010-04-12 V. Zheligovsky

Main-sequence massive stars possess convective cores that likely harbor strong dynamo action. To assess the role of core convection in building magnetic fields within these stars, we employ the 3-D anelastic spherical harmonic (ASH) code to…

太阳与恒星天体物理 · 物理学 2015-05-20 Kyle C. Augustson , Allan S. Brun , Juri Toomre

We consider the amplification and transport of a magnetic field in the collapsed core of a massive star, including both the region between the neutrinosphere and the shock, and the central, opaque core. An analytical argument explains why…

天体物理学 · 物理学 2009-11-06 Christopher Thompson , Norman Murray

We have shown the simultaneous generation of macro-scale fast flows and strong magnetic fields in the 2-temperature relativistic electron-ion plasmas of astrophysical objects due to Unified Reverse Dynamo/Dynamo mechanism. The resulting…

太阳与恒星天体物理 · 物理学 2022-01-12 K. Kotorashvili , N. L. Shatashvili

When our Sun was young it rotated much more rapidly than now. Observations of young, rapidly rotating stars indicate that many possess substantial magnetic activity and strong axisymmetric magnetic fields. We conduct simulations of dynamo…

太阳与恒星天体物理 · 物理学 2009-06-15 Benjamin P. Brown , Matthew K. Browning , Mark S. Miesch , Allan Sacha Brun , Juri Toomre

Chemically peculiar Ap and Bp stars host strong large-scale magnetic fields in the range of $200$~G up to $30$~kG, which are often considered to be the origin of fossil magnetic fields. We assess the evolution of such fossil fields during…

太阳与恒星天体物理 · 物理学 2023-06-30 Dominik R. G. Schleicher , Juan Pablo Hidalgo , Daniele Galli

The interaction between a protostellar magnetosphere and a surrounding dynamo-active accretion disc is investigated using an axisymmetric mean-field model. In all models investigated, the dynamo-generated magnetic field in the disc arranges…

天体物理学 · 物理学 2009-11-10 Brigitta von Rekowski , Axel Brandenburg