New Suns in the Cosmos. V. Stellar Rotation and Multifractality in Active Kepler Stars

Freitas, D. B. de; Nepomuceno, M. M. F.; Rios, L. D. Alves; Chagas, Maria Liduína das; Medeiros, J. R. De

doi:10.3847/1538-4357/ab2a0c

Cited by 5 publications

(10 citation statements)

References 78 publications

(99 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the latter case, the PDC and SAP timeseries, as well as the difference RTS data, are examined considering the generalized dependence of the local Hurst exponent on the timescale τ by means of the surface h(q, τ). We also consider the impact of the rotational modulation on the characterization of the multifractal properties of the light fluctuations, as already investigated by de Freitas et al (2013bde Freitas et al ( , 2016de Freitas et al ( , 2017de Freitas et al ( , 2019a, and show that such an impact depends on the timescale. Furthermore, we applied a maximum entropy spot modelling to extract information on the longitude, the area variation, and the evolutionary timescales of the active regions responsible for the rotational modulation of the stellar flux.…”

Section: Discussionmentioning

confidence: 84%

“…Recently, de Freitas et al (2019a,b) extended the field of application to timeseries showing more than one significant rotational periodicity, which can be considered as an indication of stellar differential rotation. Using a large sample of Kepler active stars, de Freitas et al (2019a) showed that in the relationship between the Hurst exponent and the relative amplitude of the differential rotation ∆P/P a strong trend of increasing ∆P/P toward larger H-index is observed. In addition, the study shows that the correlation is stronger for the most active stars in the sample.…”

Section: Origins Of Multifractality and The Impact Of Quasi-periodic ...mentioning

confidence: 99%

“…As discussed by de Freitas et al (2013a), the global Hurst exponent (Hurst 1951) is a powerful (multi)fractal indicator for analysing CoRoT and Kepler time series, which is mainly used to elucidate the persistence due to rotational modulation in the series themselves. Recently a novel technique proposed by Gu & Zhou (2010), known as the multifractal detrended moving average (MFDMA) method, has been applied for the multifractal characterization of Kepler timeseries (de Freitas et al 2017(de Freitas et al , 2019a. The MFDMA method filters out the local trends of nonstationary series by subtracting the local means.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On the multiscale behaviour of stellar activity and rotation of the planet host Kepler-30

de Freitas,

Lanza,

Gomes

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Context. The Kepler-30 system consists of a G dwarf star with a rotation period of ∼16 days and three planets orbiting almost coplanar with periods ranging from 29 to 143 days. Kepler-30 is a unique target to study stellar activity and rotation in a young solar-like star accompanied by a compact planetary system. Aims. We use about 4 years of high-precision photometry collected by the Kepler mission to investigate the fluctuations caused by photospheric convection, stellar rotation, and starspot evolution as a function of the timescale. Our main goal is to apply methods for the analysis of timeseries to find the timescales of the phenomena that affect the light variations. We correlate those timescales with periodicities in the star as well as in the planetary system. Methods. We model the flux rotational modulation induced by active regions using spot modelling and apply the Multifractal Detrending Moving Average algorithm (MFDMA) in standard and multiscale versions for analysing the behaviour of variability and light fluctuations that can be associated with stellar convection and the evolution of magnetic fields on timescales ranging from less than 1 day up to about 35 days. The light fluctuations produced by stellar activity can be described by the multifractal Hurst index that provides a measure of their persistence. Results. The spot modeling indicates a lower limit to the relative surface differential rotation of ∆Ω/Ω ∼ 0.02 ± 0.01 and suggests a short-term cyclic variation in the starspot area with a period of ∼ 34 days, virtually close to the synodic period of 35.2 days of the planet Kepler-30b. By subtracting the two timeseries of the SAP and PDC Kepler pipelines, we reduce the rotational modulation and find a 23.1-day period close to the synodic period of Kepler-30c. This period also appears in the multifractal analysis as a crossover of the fluctuation functions associated with the characteristic evolutionary timescales of the active regions in Kepler-30 as confirmed by spot modelling. These procedures and methods may be greatly useful for analysing current TESS and future PLATO data.

show abstract

Section: Discussionmentioning

confidence: 84%

Section: Origins Of Multifractality and The Impact Of Quasi-periodic ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the multiscale behaviour of stellar activity and rotation of the planet host Kepler-30

de Freitas,

Lanza,

Gomes

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Over recent years, several methods have been applied to investigate the (multi)fractal structure of time-series in astrophysical systems (e.g. de Freitas et al 2016de Freitas et al , 2017de Freitas et al , 2019aBelete et al 2018;de Franciscis et al 2019). The estimation of local fluctuations and long-term dependency of astrophysical timeseries is a problem that has recently been studied to understand the effect of long-memory processes caused by stellar rotation (de Freitas et al 2019a,b).…”

Section: Introductionmentioning

confidence: 99%

“…As discussed by de Freitas et al (2013a), the global Hurst exponent (Hurst 1951) is a powerful (multi)fractal indicator for analysing CoRoT and Kepler timeseries, which is mainly used to elucidate the persistence due to rotational modulation in the series themselves. Recently, a novel technique proposed by Gu & Zhou (2010), known as the multifractal detrended moving average (MFDMA) method, was applied for the multifractal characterisation of Kepler time-series (de Freitas et al 2017(de Freitas et al , 2019a. The MFDMA method filters out the local trends of non-stationary series by subtracting the local means.…”

Section: Introductionmentioning

confidence: 99%

Multiscale behaviour of stellar activity and rotation of the planet host Kepler-30

Freitas

Lanza

Silva

et al. 2021

A&A

Self Cite

View full text Add to dashboard Cite

Context. The Kepler-30 system consists of a G dwarf star with a rotation period of ~16 days and three planets orbiting almost coplanar with periods ranging from 29 to 143 days. Kepler-30 is a unique target with which to study stellar activity and rotation in a young solar-like star accompanied by a compact planetary system. Aims. We use about 4 yr of high-precision photometry collected by the Kepler mission to investigate the fluctuations caused by photospheric convection, stellar rotation, and starspot evolution as a function of timescale. Our main goal is to apply methods for the analysis of time-series to find the timescales of the phenomena that affect the light variations. We correlate those timescales with periodicities in the star and the planetary system. Methods. We model the flux rotational modulation induced by active regions using spot modelling and apply the Multifractal Detrending Moving Average algorithm in standard and multiscale versions to analyse the behaviour of variability and light fluctuations that can be associated with stellar convection and the evolution of magnetic fields on timescales ranging from less than 1 day up to about 35 days. The light fluctuations produced by stellar activity can be described by the multifractal Hurst index that provides a measure of their persistence. Results. The spot modelling indicates a lower limit to the relative surface differential rotation of ΔΩ∕Ω ~ 0.02 ± 0.01 and suggests a short-term cyclic variation in the starspot area with a period of ~34 days, which is close to the synodic period of 35.2 days of the planet Kepler-30b. By subtracting the two time-series of the simple aperture photometry and pre-search data conditioning Kepler pipelines, we reduce the rotational modulation and find a 23.1-day period close to the synodic period of Kepler-30c. This period also appears in the multifractal analysis as a crossover of the fluctuation functions associated with the characteristic evolutionary timescales of the active regions in Kepler-30 as confirmed by spot modelling. These procedures and methods may be greatly useful for analysing current TESS and future PLATO data.

show abstract

An innovative tool for automating classification of stellar variability through nonlinear data analytics

Syiemlieh,

Saleh,

Hazarika

et al. 2023

Astronomy and Computing

View full text Add to dashboard Cite

New Suns in the Cosmos. V. Stellar Rotation and Multifractality in Active Kepler Stars

Cited by 5 publications

References 78 publications

On the multiscale behaviour of stellar activity and rotation of the planet host Kepler-30

On the multiscale behaviour of stellar activity and rotation of the planet host Kepler-30

Multiscale behaviour of stellar activity and rotation of the planet host Kepler-30

An innovative tool for automating classification of stellar variability through nonlinear data analytics

Contact Info

Product

Resources

About