Rotation of solar‐like stars in the immediate solar neighborhood

Schmitt, J. H. M. M.; Mittag, M.

doi:10.1002/asna.202013790

Cited by 8 publications

(5 citation statements)

References 31 publications

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“…TIGRE is a dedicated instrument for the study of stellar magnetic activity. The TIGRE data of κ Ceti have previously been used by Hempelmann et al (2016) and Schmitt & Mittag (2020) for the determination of the star's rotation period. The TIGRE S-index measurements (see Fig.…”

Section: Archival S-index Measurementsmentioning

confidence: 99%

Time evolution of magnetic activity cycles in young suns: The curious case of κ Ceti

Saikia

Lüftinger

Antonova

et al. 2022

A&A

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Context. A detailed investigation of the magnetic properties of young Sun-like stars can provide valuable information on our Sun's magnetic past and its impact on the early Earth. Aims. We determine the properties of the moderately rotating young Sun-like star κ Ceti's magnetic and activity cycles using 50 years of chromospheric activity data and six epochs of spectropolarimetric observations. Methods. The chromospheric activity was determined by measuring the flux in the Ca ii H and K lines. A generalised Lomb-Scargle periodogram and a wavelet decomposition were used on the chromospheric activity data to establish the associated periodicities. The vector magnetic field of the star was reconstructed using the technique of Zeeman Doppler imaging on the spectropolarimetric observations. Results. Our period analysis algorithms detect a 3.1 year chromospheric cycle in addition to the star's well-known ∼ 6 year cycle period. Although the two cycle periods have an approximate 1:2 ratio, they exhibit an unusual temporal evolution. Additionally, the spectropolarimetric data analysis shows polarity reversals of the star's large-scale magnetic field, suggesting a ∼10 year magnetic or Hale cycle. Conclusions. The unusual evolution of the star's chromospheric cycles and their lack of a direct correlation with the magnetic cycle establishes κ Ceti as a curious young Sun. Such complex evolution of magnetic activity could be synonymous with moderately active young Suns, which is an evolutionary path that our own Sun could have taken.

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Section: Archival S-index Measurementsmentioning

confidence: 99%

Time evolution of magnetic activity cycles in young suns: The curious case of κ Ceti

Saikia

Lüftinger

Antonova

et al. 2022

A&A

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“…Unfortunately, directly measured rotation periods are available for only 99 sample stars, 62 of which belong to the valid sample. Fast-rotating stars tend to be more active and their periods easier to measure, and, indeed, 41 out of the 62 periods in the valid sample are shorter than 10 days; see for instance Schmitt & Mittag (2020) for the difficulties in measuring accurate periods in low-activity stars.…”

Section: Rotation and The Pseudo-simultaneitymentioning

confidence: 99%

The corona – chromosphere connection studied with simultaneous eROSITA and TIGRE observations

Fuhrmeister

Czesla

Robrade

et al. 2022

A&A

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Stellar activity manifests itself in a variety of different phenomena, some of which we can measure as activity tracers from different atmospheric layers of the star, typically at different wavelengths. Stellar activity is furthermore inherently time variable, therefore simultaneous measurements are necessary to study the correlation between different activity indicators. In this study we compare X-ray fluxes measured within the first all-sky survey conducted by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) instrument on board the Spectrum-Roentgen-Gamma observatory to Ca II H&K excess flux measurements RHK+, using observations made with the robotic TIGRE telescope. We created the largest sample of simultaneous X-ray and spectroscopic Ca II H&K observations of late-type stars obtained so far, and in addition, previous measurements of Ca II H&K for all sample stars were obtained. We find the expected correlation between our log(LX/Lbol) to log(RHK+) measurements, but when the whole stellar ensemble is considered, the correlation between coronal and chromospheric activity indicators does not improve when the simultaneously measured data are used. A more detailed analysis shows that the correlation of log(LX/Lbol) to log(RHK+) measurements of the pseudo-simultaneous data still has a high probability of being better than that of a random set of non-simultaneous measurements with a long time baseline between the observations. Cyclic variations on longer timescales are therefore far more important for the activity flux-flux relations than short-term variations in the form of rotational modulation or flares, regarding the addition of “noise” to the activity flux-flux correlations. Finally, regarding the question of predictability of necessarily space-based log (LX/Lbol) measurements by using ground-based chromospheric indices, we present a relation for estimating log (LX/Lbol) from RHK+ values and show that the expected error in the calculated minus observed (C-O) log (LX/Lbol) values is 0.35 dex.

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“…As an interesting aside, lower bound (13) on the planet period is remarkably close to the shortest rotation periods of field solar-type stars (Schmitt & Mittag 2020). This suggests that a moonless planet, if it migrates too close to the star, is not capable of synchronising the star rotation, and therefore gets destroyed.…”

Section: A Planet Synchronised By Its Moonmentioning

confidence: 85%

Pathways of survival for exomoons and inner exoplanets

Makarov

Efroimsky

2023

A&A

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Context. It is conceivable that a few thousand confirmed exoplanets initially harboured satellites similar to the moons of the Solar System or larger. We ask the question of whether some of them have survived over the æons of dynamical evolution to the present day. The dynamical conditions are harsh for exomoons in such systems because of the greater influence of the host star and of the tidal torque it exerts on the planet. Aims. We investigate the stability niches of exomoons around hundreds of innermost exoplanets for which the needed parameters are known today, and we determine the conditions of these moons’ long-term survival. General lower and upper bounds on the exomoon survival niches are derived for orbital separations, periods, and masses. Methods. The fate of an exomoon residing in a stability niche depends on the initial relative rate of the planet’s rotation and on the ability of the moon to synchronise the planet by overpowering the tidal action from the star. State-of-the-art models of tidal dissipation and secular orbital evolution are applied to a large sample of known exoplanet systems, which have the required estimated physical parameters. Results. We show that in some plausible scenarios, exomoons can prevent close exoplanets from spiralling into their host stars, thus extending these planets’ lifetimes. This is achieved when exomoons synchronise the rotation of their parent planets, overpowering the tidal action from the stars. Conclusions. Massive moons are more likely to survive and help their host planets maintain a high rotation rate (higher than these planets’ mean motion).

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Rotation of solar‐like stars in the immediate solar neighborhood

Cited by 8 publications

References 31 publications

Time evolution of magnetic activity cycles in young suns: The curious case of κ Ceti

Time evolution of magnetic activity cycles in young suns: The curious case of κ Ceti

The corona – chromosphere connection studied with simultaneous eROSITA and TIGRE observations

Pathways of survival for exomoons and inner exoplanets

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