A scaling relationship for non-thermal radio emission from ordered magnetospheres: from the top of the main sequence to planets
Date Issued
2021
Author(s)
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Krtička, J
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Fossati, L
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Ignace, R
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Shultz, M E
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Cerrigone, L
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•
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Bordiu, C
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•
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Oskinova, L M
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Agliozzo, C
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Todt, H
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Giarrusso, M
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Phillips, N M
•
Robrade, J
•
Abstract
In this paper, we present the analysis of incoherent non-thermal radio
emission from a sample of hot magnetic stars, ranging from early-B to early-A
spectral type. Spanning a wide range of stellar parameters and wind properties,
these stars display a commonality in their radio emission which presents new
challenges to the wind scenario as originally conceived. It was thought that
relativistic electrons, responsible for the radio emission, originate in
current sheets formed where the wind opens the magnetic field lines. However,
the true mass-loss rates from the cooler stars are too small to explain the
observed non-thermal broadband radio spectra. Instead, we suggest the existence
of a radiation belt located inside the inner-magnetosphere, similar to that of
Jupiter. Such a structure explains the overall indifference of the broadband
radio emissions on wind mass-loss rates. Further, correlating the radio
luminosities from a larger sample of magnetic stars with their stellar
parameters, the combined roles of rotation and magnetic properties have been
empirically determined. Finally, our sample of early-type magnetic stars
suggests a scaling relationship between the non-thermal radio luminosity and
the electric voltage induced by the magnetosphere's co-rotation, which appears
to hold for a broader range of stellar types with dipole-dominated
magnetospheres (like the cases of the planet Jupiter and the ultra-cool dwarf
stars and brown dwarfs). We conclude that well-ordered and stable rotating
magnetospheres share a common physical mechanism for supporting the generation
of non-thermal electrons.
Volume
507
Issue
2
Start page
1979
Issn Identifier
0035-8711
Ads BibCode
2021MNRAS.507.1979L
Rights
open.access
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