Activity cycles in members of young loose stellar associations

Abstract

Magnetic cycles have been detected in tens of solar-like stars. The relationship between the cycle properties and global stellar parameters is not fully understood yet. We searched for activity cycles in 90 solar-like stars with ages between 4 and 95 Myr aiming to investigate the properties of activity cycles in this age range. We measured the length $P_{cyc}$ of a given cycle by analyzing the long-term time-series of three activity indexes. For each star, we computed also the global magnetic activity index <IQR> that is proportional to the amplitude of the rotational modulation and is a proxy of the mean level of the surface magnetic activity. We detected activity cycles in 67 stars. Secondary cycles were also detected in 32 stars. The lack of correlation between $P_{cyc}$ and $P_{rot}$ suggest that these stars belong to the Transitional Branch and that the dynamo acting in these stars is different from the solar one. This statement is also supported by the analysis of the butterfly diagrams. We computed the Spearman correlation coefficient $r_S$ between $P_{cyc}$, <IQR> and different stellar parameters. We found that $P_{cyc}$ is uncorrelated with all the investigated parameters. The <IQR> index is positively correlated with the convective turn-over time-scale, the magnetic diffusivity time-scale ${\tau }_{diff}$, and the dynamo number $D_N$, whereas it is anti-correlated with the effective temperature $T_{eff}$, the photometric shear $\Delta {\Omega }_{\mathrm{phot}}$ and the radius $R_C$ at which the convective zone is located. We found that $P_{cyc}$ is about constant and that <IQR> decreases with the stellare age in the range 4-95 Myr. We investigated the magnetic activity of AB Dor A by merging ASAS time-series with previous long-term photometric data. We estimated the length of the AB Dor A primary cycle as $P_{cyc}=16.78\pm 2\mathrm{yr}$.

19 pages , 15 figures, accepted

References in corpus (8)

• The first WASP public data release
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• The connection between stellar activity cycles and magnetic field topology
• Looking for activity cycles in late-type Kepler stars using time-frequency analysis
• Magnetic activity on AB Doradus: Temporal evolution of starspots and differential rotation from 1988 to 1994
• Improved age constraints for the AB Dor quadruple system - The binary nature of AB Dor B
• Chromospherically Active Stars in the RAVE Survey. II. Young dwarfs in the Solar neighborhood
• X-ray Evidence for a Pole-Dominated Corona on AB Dor

Cited by in corpus (11)

• Gaia Data Release 3. Rotational modulation and patterns of colour variations in solar-like variables
• Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution
• Stellar activity and rotation of the planet host Kepler-17 from long-term space-borne photometry
• Starspot rotation rates vs. activity cycle phase: Butterfly diagrams of Kepler stars are unlike the Sun's
• On the origin of the dichotomy of stellar activity cycles
• Photometric activity cycles in fast-rotating stars: Revisiting the reality of stellar activity cycle branches
• HADES RV Programme with HARPS-N at TNG. XVI. A super-Earth in the habitable zone of the GJ 3998 multi-planet system
• Long-term stellar activity of M dwarfs: A combined K2 and TESS study of two early M-type stars
• Long-Term Activity in Photospheres of Low-Mass Stars with Strong Magnetic Fields
• Retarded Stellar Dynamo in Tidally Deformed M Dwarfs
• Activity cycles in RS CVn type stars