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Topological changes...
Topological changes in the magnetic field of LQ Hya during an activity minimum
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- Lehtinen, J. J. (författare)
- Univ Turku, Finnish Ctr Astron ESO FINCA, Vesilinnantie 5, Turku 20014, Finland.;Univ Helsinki, Dept Phys, POB 64, Helsinki 00014, Finland.
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- Käpylä, Maarit (författare)
- Stockholms universitet,Nordiska institutet för teoretisk fysik (Nordita),Aalto University, Finland; Max Planck Institute for Solar System Research, Germany,Aalto Univ, Dept Comp Sci, POB 15400, Aalto 00076, Finland.;Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.;KTH Royal Inst Technol, NORDITA, Hannes Alfvens Vag 12, S-10691 Stockholm, Sweden.;Stockholm Univ, Hannes Alfvens Vag 12, S-10691 Stockholm, Sweden.
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- Hackman, T. (författare)
- Univ Helsinki, Dept Phys, POB 64, Helsinki 00014, Finland.
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- Kochukhov, Oleg (författare)
- Uppsala universitet,Observationell astrofysik
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- Willamo, T. (författare)
- Univ Helsinki, Dept Phys, POB 64, Helsinki 00014, Finland.
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- Marsden, S. C. (författare)
- Univ Southern Queensland, Ctr Astrophys, Toowoomba, Qld 4350, Australia.
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Jeffers, S. , V (författare)
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- Henry, G. W. (författare)
- Tennessee State Univ, Ctr Excellence Informat Syst, Nashville, TN 37209 USA.
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- Jetsu, L. (författare)
- Univ Helsinki, Dept Phys, POB 64, Helsinki 00014, Finland.
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Univ Turku, Finnish Ctr Astron ESO FINCA, Vesilinnantie 5, Turku 20014, Finland;Univ Helsinki, Dept Phys, POB 64, Helsinki 00014, Finland. Nordiska institutet för teoretisk fysik (Nordita) (creator_code:org_t)
- 2022-05-02
- 2022
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 660
- Relaterad länk:
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https://doi.org/10.1...
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http://arxiv.org/pdf...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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https://urn.kb.se/re...
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https://urn.kb.se/re...
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Abstract
Ämnesord
Stäng
- Aims. Previous studies have related surface temperature maps, obtained with the Doppler imaging (DI) technique, of LQ Hya with long-term photometry. Here, we compare surface magnetic field maps, obtained with the Zeeman Doppler imaging (ZDI) technique, with contemporaneous photometry, with the aim of quantifying the star's magnetic cycle characteristics. Methods. We inverted Stokes IV spectropolarimetry, obtained with the HARPSpol and ESPaDOnS instruments, into magnetic field and surface brightness maps using a tomographic inversion code that models high signal-to-noise ratio mean line profiles produced by the least squares deconvolution (LSD) technique. The maps were compared against long-term ground-based photometry acquired with the T3 0.40 m Automatic Photoelectric Telescope (APT) at Fairborn Observatory, which offers a proxy for the spot cycle of the star, as well as with chromospheric Ca II H&K activity derived from the observed spectra. Results. The magnetic field and surface brightness maps reveal similar patterns relative to previous DI and ZDI studies: nonaxisymmetric polar magnetic field structure, void of fields at mid-latitudes, and a complex structure in the equatorial regions. There is a weak but clear tendency of the polar structures to be linked with a strong radial field and the equatorial ones with the azimuthal field. We find a polarity reversal in the radial field between 2016 and 2017 that is coincident with a spot minimum seen in the long-term photometry, although the precise relation of chromospheric activity to the spot activity remains complex and unclear. The inverted field strengths cannot be easily related with the observed spottedness, but we find that they are partially connected to the retrieved field complexity. Conclusions. This field topology and the dominance of the poloidal field component, when compared to global magnetoconvection models for rapidly rotating young suns, could be explained by a turbulent dynamo, where differential rotation does not play a major role (so-called alpha(2)Omega(2) or alpha(2) dynamos) and axi- and non-axisymmetric modes are excited simultaneously. The complex equatorial magnetic field structure could arise from the twisted (helical) wreaths often seen in these simulations, while the polar feature would be connected to the mostly poloidal non-axisymmetric component that has a smooth spatial structure.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- polarization
- stars: activity
- stars: imaging
- starspots
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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Till lärosätets databas
- Av författaren/redakt...
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Lehtinen, J. J.
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Käpylä, Maarit
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Hackman, T.
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Kochukhov, Oleg
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Willamo, T.
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Marsden, S. C.
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Jeffers, S. , V
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Henry, G. W.
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Jetsu, L.
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- NATURVETENSKAP
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Kungliga Tekniska Högskolan
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Stockholms universitet
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Uppsala universitet