On the surface magnetic fields of rapidly rotating stars with winds

1988 ◽  
Vol 335 ◽  
pp. 931 ◽  
Author(s):  
Murugesapillai Maheswaran ◽  
Joseph P. Cassinelli
Keyword(s):  
Magnetic Fields ◽  
Rotating Stars ◽  
Rapidly Rotating Stars

scholarly journals Magnetic Fields in Rapidly Rotating Stars

1973 ◽  
Vol 162 (3) ◽  
pp. 289-293
Author(s):  
M. Maheswaran ◽  
H. A. B. M. de Silva
Keyword(s):  
Magnetic Fields ◽  
Rotating Stars ◽  
Rapidly Rotating Stars

scholarly journals Magnetic Fields in Low-Mass Stars: An Overview of Observational Biases

2013 ◽  
Vol 9 (S302) ◽  
pp. 156-163 ◽  
Author(s):  
Ansgar Reiners
Keyword(s):  
Magnetic Fields ◽  
Zeeman Effect ◽  
Field Measurements ◽  
Rotating Stars ◽  
Magnetic Field Generation ◽  
Low Mass Stars ◽  
Important Indicator ◽  
Stellar Radius ◽  
Low Mass ◽  
Rapidly Rotating Stars

AbstractStellar magnetic dynamos are driven by rotation, rapidly rotating stars produce stronger magnetic fields than slowly rotating stars do. The Zeeman effect is the most important indicator of magnetic fields, but Zeeman broadening must be disentangled from other broadening mechanisms, mainly rotation. The relations between rotation and magnetic field generation, between Doppler and Zeeman line broadening, and between rotation, stellar radius, and angular momentum evolution introduce several observational biases that affect our picture of stellar magnetism. In this overview, a few of these relations are explicitly shown, and the currently known distribution of field measurements is presented.

scholarly journals Period spacings of gravity modes in rapidly rotating magnetic stars

2019 ◽  
Vol 627 ◽  
pp. A64 ◽  
Author(s):  
V. Prat ◽  
S. Mathis ◽  
B. Buysschaert ◽  
J. Van Beeck ◽  
D. M. Bowman ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Internal Magnetic Field ◽  
Rotating Stars ◽  
Frequency Shifts ◽  
Perturbative Approach ◽  
Magnetic Stars ◽  
Stellar Magnetic Fields ◽  
Rapidly Rotating Stars ◽  
The Magnetic Field

Context. Stellar magnetic fields are often invoked to explain the missing transport of angular momentum observed in models of stellar interiors. However, the properties of an internal magnetic field and the consequences of its presence on stellar evolution are largely unknown. Aims. We study the effect of an axisymmetric internal magnetic field on the frequency of gravity modes in rapidly rotating stars to check whether gravity modes can be used to detect and probe such a field. Methods. Rotation is taken into account using the traditional approximation of rotation and the effect of the magnetic field is computed using a perturbative approach. As a proof of concept, we compute frequency shifts due to a mixed (i.e. with both poloidal and toroidal components) fossil magnetic field for a representative model of a known magnetic, rapidly rotating, slowly pulsating B-type star: HD 43317. Results. We find that frequency shifts induced by the magnetic field scale with the square of its amplitude. A magnetic field with a near-core strength of the order of 150 kG (which is consistent with the observed surface field strength of the order of 1 kG) leads to signatures that are detectable in period spacings for high-radial-order gravity modes. Conclusions. The predicted frequency shifts can be used to constrain internal magnetic fields and offer the potential for a significant step forward in our interpretation of the observed structure of gravity-mode period spacing patterns in rapidly rotating stars.

scholarly journals Destruction of Be star disk by large scale magnetic fields

2016 ◽  
Vol 12 (S329) ◽  
pp. 453-453
Author(s):  
Asif ud-Doula ◽  
Stanley Owocki ◽  
Nathaniel (Dylan) Kee ◽  
Michael Vanyo
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Circumstellar Disks ◽  
Be Stars ◽  
Rotating Stars ◽  
Apparent Lack ◽  
B Stars ◽  
Large Scale Magnetic Field ◽  
Be Star ◽  
Rapidly Rotating Stars

AbstractClassical Be stars are rapidly rotating stars with circumstellar disks that come and go on time scale of years. Recent observational data strongly suggests that these stars lack the 10% incidence of global magnetic fields observed in other main-sequence B stars. Such an apparent lack of magnetic fields may indicate that Be disks are fundamentally incompatible with a significant large scale magnetic field. In this work, using numerical magnetohydrodynamics (MHD) simulations, we show that a dipole field of only 100G can lead to the quick disruption of a Be disk. Such a limit is in line with the observational upper limits for these objects.

scholarly journals Rossby Waves in Astrophysics

2021 ◽  
Vol 217 (1) ◽  
Author(s):  
T. V. Zaqarashvili ◽  
M. Albekioni ◽  
J. L. Ballester ◽  
Y. Bekki ◽  
L. Biancofiore ◽  
...  
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Magnetic Activity ◽  
Future Research ◽  
Rotating Stars ◽  
Spatial And Temporal Scales ◽  
Physical Role ◽  
Astrophysical Objects ◽  
Exoplanetary Atmospheres ◽  
Rapidly Rotating Stars

AbstractRossby waves are a pervasive feature of the large-scale motions of the Earth’s atmosphere and oceans. These waves (also known as planetary waves and r-modes) also play an important role in the large-scale dynamics of different astrophysical objects such as the solar atmosphere and interior, astrophysical discs, rapidly rotating stars, planetary and exoplanetary atmospheres. This paper provides a review of theoretical and observational aspects of Rossby waves on different spatial and temporal scales in various astrophysical settings. The physical role played by Rossby-type waves and associated instabilities is discussed in the context of solar and stellar magnetic activity, angular momentum transport in astrophysical discs, planet formation, and other astrophysical processes. Possible directions of future research in theoretical and observational aspects of astrophysical Rossby waves are outlined.

scholarly journals Learning about Stellar Dynamos from Long–term Photometry of Starspots

1991 ◽  
Vol 130 ◽  
pp. 353-369 ◽  
Author(s):  
Douglas S. Hall
Keyword(s):  
Differential Rotation ◽  
Rotation Period ◽  
Turnover Time ◽  
Rotating Stars ◽  
Photometric Variability ◽  
Solar Type ◽  
Magnetic Cycles ◽  
The Many ◽  
Rapidly Rotating Stars

AbstractSpottedness, as evidenced by photometric variability in 277 late-type binary and single stars, is found to occur when the Rossby number is less than about 2/3. This holds true when the convective turnover time versus B–V relation of Gilliland is used for dwarfs and also for subgiants and giants if their turnover times are twice and four times longer, respectively, than for dwarfs. Differential rotation is found correlated with rotation period (rapidly rotating stars approaching solid-body rotation) and also with lobe-filling factor (the differential rotation coefficient k is 2.5 times larger for F = 0 than F = 1). Also reviewed are latitude extent of spottedness, latitude drift during a solar-type cycle, sector structure and preferential longitudes, starspot lifetimes, and the many observational manifestations of magnetic cycles.

scholarly journals P-modes in rapidly rotating stars: Looking for regular patterns in synthetic asymptotic spectra

2010 ◽  
Vol 331 (9-10) ◽  
pp. 1053-1056 ◽  
Author(s):  
F. Lignières ◽  
B. Georgeot ◽  
J. Ballot
Keyword(s):  
Rotating Stars ◽  
Rapidly Rotating Stars ◽  
Regular Patterns
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