Wavelet analysis of stellar rotation and other periodicities

Freitas, D. B. de; Leão, I. de C.; Martins, B. L. Canto; Medeiros, J. R. De

doi:10.48550/arxiv.1009.5090

Cited by 2 publications

(3 citation statements)

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“…Wavelet maps provide important diagnostics for the behavior of starspot dynamics (de Freitas et al 2010;Bonomo & Lanza 2012;Sello 2013). The main period, as observed in the wavelet maps and power spectra, is typically the rotation period, as is commonly assumed in the literature (e.g., Garcia et al 2014;McQuillan et al 2013aMcQuillan et al ,b, 2014Nielsen et al 2013;Walkowicz & Basri 2013;Reinhold et al 2013), except for approximately 5% of a sample (De Medeiros et al 2013, see also § 2.1).…”

Section: Resultsmentioning

confidence: 87%

THE ROTATIONAL BEHAVIOR OFKEPLERSTARS WITH PLANETS

Paz-Chinchón¹,

Leão²,

Bravo³

et al. 2015

ApJ

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We analyzed the host stars of the present sample of confirmed planets detected by Kepler and Kepler Objects of Interest (KOI) to compute new photometric rotation periods and to study the behavior of their angular momentum. Lomb-Scargle periodograms and wavelet maps were computed for 3, 807 stars. For 540 of these stars, we were able to detect rotational modulation of the light curves at a significance level of greater than 99%. For 63 of these 540 stars, no rotation measurements were previously available in the literature. According to the published masses and evolutionary tracks of the stars in this sample, the sample is composed of M-to F-type stars (with masses of 0.48-1.53 M ⊙ ) with rotation periods that span a range of 2 to 89 days. These periods exhibit an excellent agreement with previously reported (for the stars for which such values are available), and the observed rotational period distribution strongly agrees with theoretical predictions. Furthermore, for the 540 sources considered here, the stellar angular momentum provides an important test of Kraft's relation based on the photometric rotation periods. Finally, this study directly contributes in a direct approach to our understanding of how angular momentum is distributed between the host star and its (detected) planetary system; the role of angular momentum exchange in such systems is an unavoidable piece of the stellar rotation puzzle.

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Section: Resultsmentioning

confidence: 87%

THE ROTATIONAL BEHAVIOR OFKEPLERSTARS WITH PLANETS

Paz-Chinchón¹,

Leão²,

Bravo³

et al. 2015

ApJ

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“…Following the method of Meyers et al (1993), the relationship between the equivalent Fourier period and the wavelet scale can be derived analytically for a particular wavelet function, ψ, by substituting a cosine wave of a known frequency into the convolution of the mother wavelet with the Discrete Fourier Transform (DFT) (Torrence & Compo 1998). The use of the CWT power spectrum as a way to detect periodicities and study other astrophysical properties such as pulsation and rotation has already been studied by de Freitas et al (2010) and Bravo et al (2014).…”

Section: Wavelet Power Spectrummentioning

confidence: 99%

“…Wavelets have been applied in several astronomy areas like astronomical signal processing (Starck & Murtagh 1994;Núñez & Otazu 1996;Starck et al 1998); redshift spectra study (Machado et al 2013); cosmic microwave background (Moudden et al 2005), baryon acoustic oscillation analysis (Arnalte-Mur et al 2012); solar activity (Aschwanden et al 1998;Giménez de Castro et al 2001); stellar activity, pulsation and rotation analysis (de Freitas et al 2010;Bravo et al 2014); signal detection (Szatmary et al 1994;Fors et al 2008;Otazu et al 2002;Régulo et al 2007); galaxy distribution morphology (Antoja et al 2012) and light curve noise analysis (Cubillos et al 2017), and filtering (Carter & Winn 2009;Grziwa et al 2014Grziwa & Pätzold 2016;Waldmann 2014).…”

Section: Introductionmentioning

confidence: 99%

TFAW: Wavelet-based signal reconstruction to reduce photometric noise in time-domain surveys

Ser

Fors

Núñez

2018

A&A

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Context. There have been many efforts to correct systematic effects in astronomical light curves to improve the detection and characterization of planetary transits and astrophysical variability. Algorithms like the Trend Filtering Algorithm (TFA) use simultaneouslyobserved stars to measure and remove systematic effects, and binning is used to reduce high-frequency random noise. Aims. We present TFAW, a wavelet-based modified version of TFA. TFAW aims first, to increase the periodic signal detection and second, to return a detrended and de-noised signal without modifying its intrinsic characteristics. Methods. We modify TFA's frequency analysis step adding a Stationary Wavelet Transform filter to perform an initial noise and outlier removal and increase the detection of variable signals. A wavelet-based filter is added to TFA's signal reconstruction to perform an adaptive characterization of the noise-and trend-free signal and the underlying noise contribution at each iteration while preserving astrophysical signals. We carried out tests over simulated sinusoidal and transit-like signals to assess the effectiveness of the method and applied TFAW to real light curves from TFRM. We also studied TFAW's application to simulated multiperiodic signals.Results. TFAW improves the signal detection rate by increasing the signal detection efficiency (SDE) up to a factor ∼2.5× for low SNR light curves. For simulated transits, the transit detection rate improves by a factor ∼2-5× in the low-SNR regime compared to TFA. TFAW signal approximation performs up to a factor ∼2× better than bin averaging for planetary transits. The standard deviations of simulated and real TFAW light curves are ∼40% better compared to TFA. TFAW yields better MCMC posterior distributions and returns lower uncertainties, less biased transit parameters and narrower ( ∼10×) credibility intervals for simulated transits. TFAW is also able to improve the characterization of multiperiodic signals. We present a newly-discovered variable star from TFRM.

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Wavelet analysis of stellar rotation and other periodicities

Cited by 2 publications

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THE ROTATIONAL BEHAVIOR OFKEPLERSTARS WITH PLANETS

THE ROTATIONAL BEHAVIOR OFKEPLERSTARS WITH PLANETS

TFAW: Wavelet-based signal reconstruction to reduce photometric noise in time-domain surveys

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