Direct evidence of a full dipole flip during the magnetic cycle of a sun-like star

Saikia, S. Boro; Lueftinger, T.; Jeffers, S. V.; Folsom, C. P.; See, Victor; Petit, P.; Marsden, S. C.; Vidotto, A. A.; Morin, J.; Reiners, A.; Guêdel, M.

doi:10.1051/0004-6361/201834347

Cited by 40 publications

(24 citation statements)

References 33 publications

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“…S/N = 30 000, 80 000, guided by typical and very good signal-to-noise-ratios of current observations, see e.g. Jeffers et al (2014); Boro Saikia et al (2018), and a S/N = 425 000 which corresponds to 3 % of the maximum amplitude of all Stokes V profiles along the cycle. It was not possible to extract reliable maps using a S/N = 30 000 or 80 000 as the Stokes V profiles become too noisy.…”

Section: Map Selection and Stokes Profiles Modellingsupporting

confidence: 58%

“…Their magnetic cycle periods are shorter than the solar 22-yr magnetic cycle with ≈ 240 days and ≈ 14 years for τ Boo and 61 Cyg A, respectively. In particular, the slightly older and cooler K dwarf 61 Cyg A shows a solar-like behaviour in its dipolar field being strongest at activity minimum and weakest at activity maximum (Boro Saikia et al 2018). Boro Saikia et al (2016) showed also that the axisymmetry is in anti-phase with the chromospheric activity and the magnetic field topology becomes more complex during the activity maximum.…”

Section: Introductionmentioning

confidence: 97%

“…Stars other than the Sun also show activity cycles. The Zeeman-Doppler-Imaging technique (ZDI, Semel 1989;Donati & Brown 1997) is capable of mapping the large-scale magnetic fields of stars and unveiling global magnetic field reversals that are in phase with the chromospheric activity cycle in a way that is similar to our Sun for three stars: the F7 dwarf τ Boo (Jeffers et al 2018) (age = 0.9 ± 0.5 Gyr, Borsa et al (2015)), the K dwarf 61 Cyg A (Boro Saikia et al 2016Saikia et al , 2018) (age = 6 Gyr, Kervella et al (2008)) and ι Hor (Alvarado-Gomez et al, in prep.) (age = 0.88 Gyr, Stanke et al (2006)).…”

Section: Introductionmentioning

confidence: 99%

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Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging

Lehmann

Hussain

Vidotto

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We are reaching the point where spectropolarimetric surveys have run for long enough to reveal solar-like magnetic activity cycles. In this paper we investigate what would be the best strategy to identify solar-like magnetic cycles and ask which large-scale magnetic field parameters best follow a solar-type magnetic cycle and are observable with the Zeeman-Doppler-Imaging (ZDI) technique. We approach these questions using the 3D non-potential flux transport simulations of Yeates & Mackay (2012) modelling the solar vector magnetic field over 15 years (centred on solar cycle 23). The flux emergence profile was extracted from solar synoptic maps and used as input for a photospheric flux transport model in combination with a non-potential coronal evolution model. We synthesise spectropolarimetric data from the simulated maps and reconstruct them using ZDI. The ZDI observed solar cycle is set into the context of other cool star observations and we present observable trends of the magnetic field topology with time, sunspot number and S-index. We find that the axisymmetric energy fraction is the best parameter of the ZDI detectable large-scale field to trace solar-like cycles. Neither the surface averaged large-scale field or the total magnetic energy is appropriate. ZDI seems also to be able to recover the increase of the toroidal energy with S-index. We see further that ZDI might unveil hints of the dynamo modes that are operating and of the global properties of the small-scale flux emergence like active latitudes.

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Section: Map Selection and Stokes Profiles Modellingsupporting

confidence: 58%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging

Lehmann

Hussain

Vidotto

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…However, the magnetic cycle does not correspond to the star's detected chromospheric activity cycles (5.9 and 12.2 yr, Baliunas et al 1995). Only 61 Cyg A (K5V; Boro Saikia et al 2016Saikia et al , 2018b and τ Boo ( F8V; Donati et al 2008;Fares et al 2009Fares et al , 2013Mengel et al 2016;Jeffers et al 2018) are currently known to have solar-like magnetic cycles where the large-scale field polarity reverses in phase with chromospheric activity cycles.…”

Section: Bac K G Ro U N Dmentioning

confidence: 98%

Magnetic field and chromospheric activity evolution of HD 75332: a rapid magnetic cycle in an F star without a hot Jupiter

Brown

Marsden

Mengel

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Studying cool star magnetic activity gives an important insight into the stellar dynamo and its relationship with stellar properties, as well as allowing us to place the Sun’s magnetism in the context of other stars. Only 61 Cyg A (K5V) and τ Boo (F8V) are currently known to have magnetic cycles like the Sun’s, where the large-scale magnetic field polarity reverses in phase with the star’s chromospheric activity cycles. τ Boo has a rapid ∼240 d magnetic cycle, and it is not yet clear whether this is related to the star’s thin convection zone or if the dynamo is accelerated by interactions between τ Boo and its hot Jupiter. To shed light on this, we studied the magnetic activity of HD 75332 (F7V) which has similar physical properties to τ Boo and does not appear to host a hot Jupiter. We characterized its long-term chromospheric activity variability over 53 yr and used Zeeman Doppler Imaging to reconstruct the large-scale surface magnetic field for 12 epochs between 2007 and 2019. Although we observe only one reversal of the large-scale magnetic dipole, our results suggest that HD 75332 has a rapid ∼1.06 yr solar-like magnetic cycle where the magnetic field evolves in phase with its chromospheric activity. If a solar-like cycle is present, reversals of the large-scale radial field polarity are expected to occur at around activity cycle maxima. This would be similar to the rapid magnetic cycle observed for τ Boo, suggesting that rapid magnetic cycles may be intrinsic to late-F stars and related to their shallow convection zones.

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“…The coordinated spectropolarimetric observations that provide stellar magnetic field with TESS, HST and X-ray observations (XMM-Newton and NICER mission) are currently in place to provide epoch specific model inputs and outputs that are required to check the model predictions. Recent spectropolarimetric observations of another active star, K dwarf, 61 Cyg A, show that the star's magnetic field has undergone full dipole flip during the magnetic cycle (Boro Saikia et al, 2018). Such data-driven models are required in order to characterize the range of variations of ionizing radiation fluxes and their timescale in order to assess the impact of the stellar high-energy radiation onto habitability of exoplanets.…”

Section: Winds From Active Starsmentioning

confidence: 99%

Impact of space weather on climate and habitability of terrestrial-type exoplanets

Airapetian

Barnes

Cohen

et al. 2019

International Journal of Astrobiology

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187

141

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The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.

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Direct evidence of a full dipole flip during the magnetic cycle of a sun-like star

Cited by 40 publications

References 33 publications

Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging

Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging

Magnetic field and chromospheric activity evolution of HD 75332: a rapid magnetic cycle in an F star without a hot Jupiter

Impact of space weather on climate and habitability of terrestrial-type exoplanets

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