Production of magnetic fields in the interiors of stars and several effects on stellar evolution

In this paper some thoughts and problems are presented from the viewpoint that the evolution of stars may play a key role in generating magnetic fields which, in turn, may affect the mixing of nuclearly processed elements from the stellar interior to the surface. The relevant parameter is stellar rotation which, upon interaction with convective turbulence driven by thermal instabilities, leads to the generation of magnetic fields. A possible connection to Bidelman's hypothesis on the evolutionary status of Ap stars is also discussed in the context of a post-core-helium-flash hypothesis.

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Discovery of kilogauss magnetic fields on the nearby white dwarfs WD 1105–340 and WD 2150+591

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834638 ◽

2019 ◽

Vol 623 ◽

pp. A46 ◽

Cited By ~ 4

Author(s):

J. D. Landstreet ◽

S. Bagnulo

Keyword(s):

Magnetic Fields ◽

Stellar Evolution ◽

White Dwarfs ◽

Weak Field ◽

Field Structure ◽

Small Sample ◽

Dipolar Field ◽

Surface Field ◽

Clear Link ◽

Statistical Studies

Magnetic fields are present in roughly 10% of white dwarfs. These fields affect the structure and evolution of such stars, and may provide clues about their earlier evolution history. Particularly important for statistical studies is the collection of high-precision spectropolarimetric observations of (1) complete magnitude-limited samples and (2) complete volume-limited samples of white dwarfs. In the course of one of our surveys we have discovered previously unknown kG-level magnetic fields on two nearby white dwarfs, WD 1105–340 and WD 2150+591. Both stars are brighter than mV = 15. WD 2150+591 is within the 20 pc volume around the Sun, while WD 1105–340 is just beyond 25 pc in distance. These discoveries increase the small sample of such weak-field white dwarfs from 21 to 23 stars. Our data appear consistent with roughly dipolar field topology, but it also appears that the surface field structure may be more complex on the older star than on the younger one, a result similar to one found earlier in our study of the weak-field stars WD 2034+372 and WD 2359–434. This encourages further efforts to uncover a clear link between magnetic morphology and stellar evolution.

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Magnetic fields in white dwarfs and stellar evolution

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2004.08482.x ◽

2004 ◽

Vol 355 (3) ◽

pp. L13-L16 ◽

Cited By ~ 35

Author(s):

C. A. Tout ◽

D. T. Wickramasinghe ◽

L. Ferrario

Keyword(s):

Magnetic Fields ◽

Stellar Evolution ◽

White Dwarfs

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Spectropolarimetric study of selected cool supergiants

Proceedings of the International Astronomical Union ◽

10.1017/s174392131400711x ◽

2014 ◽

Vol 9 (S307) ◽

pp. 369-370

Author(s):

V. Butkovskaya ◽

S. Plachinda ◽

D. Baklanova

Keyword(s):

Magnetic Fields ◽

Stellar Evolution ◽

Good Opportunity ◽

Classical Cepheids

AbstractCool supergiants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. We present the results of spectropolarimetric study of the cool supergiants and classical Cepheids η Aql and ζ Gem.

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Dynamo-generated magnetic fields in fast rotating single giants

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309031020 ◽

2008 ◽

Vol 4 (S259) ◽

pp. 433-434 ◽

Cited By ~ 6

Author(s):

Renada Konstantinova-Antova ◽

Michel Aurière ◽

Klaus-Peter Schröder ◽

Pascal Petit

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Stellar Evolution ◽

Red Giants ◽

Good Opportunity ◽

Early Results ◽

First Time ◽

Fast Rotating

AbstractRed giants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. Using the spectro-polarimeter NARVAL of the Telescope Bernard Lyot (TBL), Pic du Midi, France and the LSD technique we began a survey of magnetic fields in single G-K-M giants. Early results include 6 MF-detections with fast rotating giants, and for the first time a magnetic field was detected directly in an evolved M-giant: EK Boo. Our results could be explained in the terms of α–ω dynamo operating in these giants.

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Physics under the bonnet of a stellar evolution code

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316006189 ◽

2015 ◽

Vol 11 (A29B) ◽

pp. 600-607

Author(s):

Richard J. Stancliffe

Keyword(s):

Magnetic Fields ◽

Stellar Evolution ◽

Reaction Rates ◽

Computational Method ◽

Atomic Diffusion ◽

Stellar Models ◽

Convective Boundaries ◽

The Way

AbstractJust how good are modern stellar models? Providing a rigorous assessment of the uncertainties is difficult because of the multiplicity of input physics. Some of the ingredients are reasonably well-known (like reaction rates and opacities). Others are not so good, with convection standing out as a particularly obvious example. In some cases, it is not clear what the ingredients should be: what role do atomic diffusion, rotation, magnetic fields, etc. play in stellar evolution? All this is then compounded by computational method. In converting all this physics into something we can implement in a 1D evolution code, we are forced to make choices about the way the equations are solved, how we will treat mixing at convective boundaries, etc. All of this can impact the models one finally generates. In this review, I will attempt to assess the uncertainties associated with the ingredients and methods used by stellar evolution modellers, and what their impacts may be on the science that we wish to do.

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Stellar models of rotating, pre-main sequence low-mass stars with magnetic fields

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314001847 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 112-113 ◽

Cited By ~ 1

Author(s):

Luiz T. S. Mendes ◽

Natália R. Landin ◽

Luiz P. R. Vaz

Keyword(s):

Magnetic Fields ◽

Stellar Evolution ◽

Large Scale ◽

Main Sequence ◽

Stellar Structure ◽

Low Mass Stars ◽

Large Scale Magnetic Field ◽

Low Mass ◽

Structure Equations ◽

Stellar Models

AbstractWe report our present efforts for introducing magnetic fields in the ATON stellar evolution code code, which now evolved to truly modifying the stellar structure equations so that they can incorporate the effects of an imposed, large-scale magnetic field. Preliminary results of such an approach, as applied to low-mass stellar models, are presented and discussed.

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Butterfly diagram of a Sun-like star observed using asteroseismology

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834251 ◽

2018 ◽

Vol 619 ◽

pp. L9 ◽

Cited By ~ 4

Author(s):

M. Bazot ◽

M. B. Nielsen ◽

D. Mary ◽

J. Christensen-Dalsgaard ◽

O. Benomar ◽

...

Keyword(s):

Magnetic Fields ◽

Stellar Evolution ◽

Theoretical Models ◽

Observational Constraint ◽

Stellar Rotation ◽

Magnetic Field Generation ◽

Rotation Rates ◽

Butterfly Diagram ◽

Stellar Magnetic Fields ◽

First Time

Stellar magnetic fields are poorly understood, but are known to be important for stellar evolution and exoplanet habitability. They drive stellar activity, which is the main observational constraint on theoretical models for magnetic field generation and evolution. Starspots are the main manifestation of the magnetic fields at the stellar surface. In this study we measured the variation in their latitude with time, called a butterfly diagram in the solar case, for the solar analogue HD 173701 (KIC 8006161). To this end, we used Kepler data to combine starspot rotation rates at different epochs and the asteroseismically determined latitudinal variation in the stellar rotation rates. We observe a clear variation in the latitude of the starspots. It is the first time such a diagram has been constructed using asteroseismic data.

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