Activity-rotation in the dM4 star Gl 729. A possible chromospheric cycle

Abstract

Recently, new debates about the role of layers of strong shear have emerged in stellar dynamo theory. Further information on the long-term magnetic activity of fully convective stars could help determine whether their underlying dynamo could sustain activity cycles similar to the solar one. We performed a thorough study of the short- and long-term magnetic activity of the young active dM4 star Gl 729. First, we analyzed long-cadence $K2$ photometry to characterize its transient events (e.g., flares) and global and surface differential rotation. Then, from the Mount Wilson $S$-indexes derived from CASLEO spectra and other public observations, we analyzed its long-term activity between 1998 and 2020 with four different time-domain techniques to detect cyclic patterns. Finally, we explored the chromospheric activity at different heights with simultaneous measurements of the H$\alpha$ and the Na I D indexes, and we analyzed their relations with the $S$-Index. We found that the cumulative flare frequency follows a power-law distribution with slope $\sim -0.73$ for the range $10^{32}$ to $10^{34}$ erg. We obtained $P_{rot}=(2.848\pm 0.001)$ days, and we found no evidence of differential rotation. We also found that this young active star presents a long-term activity cycle with a length of $\text{about four}$ years; there is less significant evidence of a shorter cycle of $0.8$ year. The star also shows a broad activity minimum between 1998 and 2004. We found a correlation between the S index, on the one hand, and the H$\alpha$ the Na I D indexes, on the other hand, although the saturation level of these last two indexes is not observed in the Ca lines. Because the maximum-entropy spot model does not reflect migration between active longitudes, this activity cycle cannot be explained by a solar-type dynamo. It is probably caused by an ${\alpha }^2$-dynamo.

References in corpus (63)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• Kepler Flares I. Active and Inactive M dwarfs
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• Spectroscopic Properties of Cool Stars in the SDSS: An Analysis of Magnetic Activity and a Search for Subdwarfs
• Stellar Flares from the First Tess Data Release: Exploring a New Sample of M-dwarfs
• The Sloan Digital Sky Survey Data Release 7 Spectroscopic M Dwarf Catalog I: Data
• Stellar Activity Masquerading as Planets in the Habitable Zone of the M dwarf Gliese 581
• Trumpeting M Dwarfs with CONCH-SHELL: a Catalog of Nearby Cool Host-Stars for Habitable ExopLanets and Life
• The stellar rotation--activity relationship in fully convective M dwarfs
• Rotation and magnetism of Kepler pulsating solar-like stars. Towards asteroseismically calibrated age-rotation relations
• The CARMENES search for exoplanets around M dwarfs: High-resolution optical and near-infrared spectroscopy of 324 survey stars
• Characterizing the Cool KOIs III. KOI-961: A Small Star with Large Proper Motion and Three Small Planets
• Large-scale alpha^2-dynamo in low-mass stars and brown dwarfs
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity
• Solar-type dynamo behaviour in fully convective stars without a tachocline
• A catalogue of rotation and activity in early-M stars
• Magnetic activity in the HARPS M-dwarf sample. The rotation-activity relationship for very low-mass stars through R'HK
• Fluxes in Hαand Ca II H and K for a sample of Southern stars
• Frequent flaring in the TRAPPIST-1 system - unsuited for life?
• A rotational and variability study of a large sample of PMS stars in NGC 2264
• BANYAN. III. Radial velocity, Rotation and X-ray emission of low-mass star candidates in nearby young kinematic groups
• SOAP. A tool for the fast computation of photometry and radial velocity induced by stellar spots
• BGLS: A Bayesian formalism for the generalised Lomb-Scargle periodogram
• A candidate super-Earth planet orbiting near the snow line of Barnard's star
• Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program II. Activity and radial velocity
• The HARPS search for southern extra-solar planets. XXXVIII. Bayesian re-analysis of three systems. New super-Earths, unconfirmed signals, and magnetic cycles
• Metallicities & Activities of Southern Stars
• UV habitable zones around M stars
• Optical, UV, and X-Ray Evidence for a 7-Year Stellar Cycle in Proxima Centauri
• CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series
• MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri
• Magnetic Activity Cycles in the Exoplanet Host Star epsilon Eridani
• Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs
• The HARPS search for southern extra-solar planets. XXXI. Magnetic activity cycles in solar-type stars: statistics and impact on precise radial velocities
• Semi-empirical Modeling of the Photosphere, Chromosphere, Transition Region, and Corona of the M-dwarf Host Star GJ 832
• Tracers of Chromospheric Structure I: Observations of Ca II K and H alpha in M Dwarfs
• Disentangling Planets and Stellar Activity for Gliese 667C
• Stellar activity as noise in exoplanet detection II. Application to M dwarfs
• The Na I D resonance lines in main sequence late-type stars
• Comparing different approaches to model the rotational modulation of the Sun as a star
• Magnetic cycles in a dynamo simulation of fully convective M-star Proxima Centauri
• Finding flares in Kepler data using machine learning tools
• The SOPHIE search for northern extrasolar planets. XIV. A temperate ($T_{\mathrm{eq}}\sim 300$ K) super-earth around the nearby star Gliese 411
• A possible activity cycle in Proxima Centauri
• Starspot activity and rotation of the planet-hosting star Kepler-17
• K2 Ultracool Dwarfs Survey II: The White Light Flare Rate of Young Brown Dwarfs
• A Catalog of M-dwarf Flares with ASAS-SN
• First long-term activity study of AU Microscopii: a possible chromospheric cycle
• X-Ray Flaring on the dMe Star, Ross 154
• Long-term chromospheric activity in southern M dwarfs: Gl 229 A and Gl 752 A
• Possible chromospheric activity cycles in AD Leo
• The Stellar Variability Noise Floor for Transiting Exoplanet Photometry with PLATO
• The spectroscopic binary system Gl 375. I. Orbital parameters and chromospheric activity
• Robustness of oscillatory ${\alpha }^2$ dynamos in spherical wedges
• Ross 128 -- GL 447A possible activity cycle for a slow-rotating fully-convective star
• An application of a solar-type dynamo model for Epsilon Eridani

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