Estimating activity cycles with probabilistic methods II. The Mount Wilson Ca H&K data

Abstract

Debate over the existence of branches in the stellar activity-rotation diagrams continues. Application of modern time series analysis tools to study the mean cycle periods in chromospheric activity index is lacking. We develop such models, based on Gaussian processes, for one-dimensional time series and apply it to the extended Mount Wilson Ca H&K sample. Our main aim is to study how the previously commonly used assumption of strict harmonicity of the stellar cycles as well as handling of the linear trends affects the results. We introduce three methods of different complexity, starting with the simple Bayesian harmonic model and followed by Gaussian Process models with periodic and quasi-periodic covariance functions. We confirm the existence of two populations in the activity-period diagram. We find only one significant trend in the inactive population, namely that the cycle periods get shorter with increasing rotation. This is in contrast with earlier studies, that postulate the existence of trends in both of the populations. In terms of rotation to cycle period ratio, our data is consistent with only two activity branches such that the active branch merges together with the transitional one. The retrieved stellar cycles are uniformly distributed over the R'HK activity index, indicating that the operation of stellar large-scale dynamos carries smoothly over the Vaughan-Preston gap. At around the solar activity index, however, indications of a disruption in the cyclic dynamo action are seen. Our study shows that stellar cycle estimates depend significantly on the model applied. Such model-dependent aspects include the improper treatment of linear trends, while the assumption of strict harmonicity can result in the appearance of double cyclicities that seem more likely to be explained by the quasi-periodicity of the cycles.

References in corpus (42)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Fast and scalable Gaussian process modeling with applications to astronomical time series
• Chromospheric activity catalogue of 4454 cool stars. Questioning the active branch of stellar activity cycles
• Inferring probabilistic stellar rotation periods using Gaussian processes
• Solar-type dynamo behaviour in fully convective stars without a tachocline
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• On differential rotation and overshooting in solar-like stars
• BGLS: A Bayesian formalism for the generalised Lomb-Scargle periodogram
• The Mount Wilson Observatory S-index of the Sun
• Stellar Evidence that the Solar Dynamo may be in Transition
• Reconciling solar and stellar magnetic cycles with nonlinear dynamo simulations
• Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
• Magnetic cycles at different ages of stars
• Exploring the $P_{cyc}$ vs $P_{rot}$ relation with flux transport dynamo models of solar-like stars
• Evolution of coexisting long and short period stellar activity cycles
• Activity trends in young solar-type stars
• Magnetic Evolution and the Disappearance of Sun-like Activity Cycles
• Evidence for photometric activity cycles in 3203 Kepler stars
• Local models of stellar convection: Reynolds stresses and turbulent heat transport
• Extended subadiabatic layer in simulations of overshooting convection
• Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
• On the cause of solar-like equatorward migration in global convective dynamo simulations
• Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars
• The relation between stellar magnetic field geometry and chromospheric activity cycles II: The rapid 120 day magnetic cycle of Tau Bootis
• Dynamo cycles in global convection simulations of solar-like stars
• Quenching and anisotropy of hydromagnetic turbulent transport
• Helicity inversion in spherical convection as a means for equatorward dynamo wave propagation
• Consequences of high effective Prandtl number on solar differential rotation and convective velocity
• Solar dynamo models with alpha-effect and turbulent pumping from local 3D convection calculations
• Alpha effect due to buoyancy instability of a magnetic layer
• Activity cycles in members of young loose stellar associations
• The continuous period search method and its application to the young solar analogue HD 116956
• Enhanced stellar activity for slow antisolar differential rotation?
• Nonparametric Bayesian Estimation of Periodic Functions
• The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo
• Using Gaussian processes to model light curves in the presence of flickering: the eclipsing cataclysmic variable ASASSN-14ag
• Impact of MHD Turbulence on Thermal Wind Balance in the Sun
• Robust detection of quasi-periodic variability: A HAWKI mini survey of late T dwarfs
• Robustness of oscillatory ${\alpha }^2$ dynamos in spherical wedges
• Analytic solution of an oscillatory migratory alpha^2 stellar dynamo
• Multiperiodicity, modulations and flip-flops in variable star light curves III. Carrier fit analysis of LQ Hya photometry for 1982-2014
• Estimating activity cycles with probabilistic methods I. Bayesian Generalised Lomb-Scargle Periodogram with Trend

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• Chromospheric activity catalogue of 4454 cool stars. Questioning the active branch of stellar activity cycles
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• Far-Ultraviolet Activity Levels of F, G, K, and M dwarf Exoplanet Host Stars
• Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
• An X-ray activity cycle on the young solar-like star $\epsilon \mathrm{Eridani}$
• Dynamo cycles in global convection simulations of solar-like stars
• Mean field models of flux transport dynamo and meridional circulation in the Sun and stars
• Common dynamo scaling in slowly rotating young and evolved stars
• The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa from Asteroseismology with TESS
• Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution
• Stellar dynamos in the transition regime: multiple dynamo modes and anti-solar differential rotation
• Turbulent processes and mean-field dynamo
• Zeeman-Doppler imaging of five young solar-type stars
• Waldmeier Effect in Stellar Cycles
• Extending the FIP bias sample to magnetically active stars. Challenging the FIP bias paradigm?
• Transition from spot to faculae domination -- An alternate explanation for the dearth of intermediate \textit{Kepler} rotation periods
• Topological changes in the magnetic field of LQ Hya during an activity minimum
• Magnetic field and chromospheric activity evolution of HD75332: a rapid magnetic cycle in an F star without a hot Jupiter
• Exploring cycle period and parity of stellar magnetic activity with dynamo modeling
• Rotational dependence of turbulent transport coefficients in global convective dynamo simulations of solar-like stars
• A Knee-Point in the Rotation-Activity Scaling of Late-type Stars with a Connection to Dynamo Transitions
• On the origin of the dichotomy of stellar activity cycles
• Solar dynamo cycle variations with a rotational period
• A collage of small planets from the Lick Carnegie Exoplanet Survey : Exploring the super-Earth and sub-Neptune mass regime
• A BCool survey of stellar magnetic cycles
• Shapes of stellar activity cycles
• A review of planetary systems around HD 99492, HD 147379 and HD 190007 with HARPS-N
• Revisiting the cycle-rotation connection for late-type stars
• Estimating activity cycles with probabilistic methods I. Bayesian Generalised Lomb-Scargle Periodogram with Trend
• The Dependence of Stellar Activity Cycles on Effective Temperature
• An application of a solar-type dynamo model for Epsilon Eridani
• Photometric activity cycles in fast-rotating stars: Revisiting the reality of stellar activity cycle branches
• Is the primary CoRoT target HD43587 under a Maunder minimum phase?
• Mean field dynamo action in shear flows. I: fixed kinetic helicity
• Small-scale and large-scale dynamos in global convection simulations of solar-like stars
• Multicomponent Activity Cycles using Hilbert-Huang Analysis
• Magnetic field morphologies in convective zones influenced by a turbulent surface layer
• Prediction of short stellar activity cycles using derived and established empirical relations between activity and rotation periods
• Solar-like dynamos and rotational scaling of cycles from star-in-a-box simulations