Three stage period analysis and complementary methods

Jetsu, L.; Pelt, J.

doi:10.1051/aas:1999411

Cited by 25 publications

(30 citation statements)

References 12 publications

(14 reference statements)

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“…A complete description of the method can be found in Lehtinen et al (2011). The CPS method has been developed from the three stage period analysis (TSPA) by Jetsu & Pelt (1999). The CPS uses a sliding window to divide the data into shorter datasets and then determines local models using a variable Kth-order Fourier series:…”

Section: Discussionmentioning

confidence: 99%

Spot activity of the RS Canum Venaticorum starσGeminorum

Kajatkari¹,

Hackman²,

Jetsu³

et al. 2014

A&A

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Aims. We model the photometry of RS CVn star σ Geminorum to obtain new information on the changes of the surface starspot distribution, that is, activity cycles, differential rotation, and active longitudes. Methods. We used the previously published continuous period search (CPS) method to analyse V-band differential photometry obtained between the years 1987 and 2010 with the T3 0.4 m Automated Telescope at the Fairborn Observatory. The CPS method divides data into short subsets and then models the light-curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period, and light-curve minima. These light-curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes. Results. We confirm the presence of two previously found stable active longitudes, synchronised with the orbital period P orb = 19. d 60, and found eight events where the active longitudes are disrupted. The epochs of the primary light-curve minima rotate with a shorter period P min,1 = 19.d 47 than the orbital motion. If the variations in the photometric rotation period were to be caused by differential rotation, this would give a differential rotation coefficient of α ≥ 0.103. Conclusions. The presence of two slightly different periods of active regions may indicate a superposition of two dynamo modes, one stationary in the orbital frame and the other one propagating in the azimuthal direction. Our estimate of the differential rotation is much higher than previous results. However, simulations show that this may be caused by insufficient sampling in our data.

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Section: Discussionmentioning

confidence: 99%

Spot activity of the RS Canum Venaticorum starσGeminorum

Kajatkari¹,

Hackman²,

Jetsu³

et al. 2014

A&A

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“…However, empirical evidence tying the cratering record on Earth to Galactic perturbations remains controversial (Jetsu and Pelt, 2000). Marochnik (1984) and Bal´azs (1988) argued that the placement of the Sun's Galactic orbit very near the corotation circle is an important requirement for habitability.…”

Section: The Galactic Habitable Zonementioning

confidence: 99%

Habitable Zones in the Universe

González

2005

Orig Life Evol Biosph

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Abstract. Habitability varies dramatically with location and time in the universe. This was recognized centuries ago, but it was only in the last few decades that astronomers began to systematize the study of habitability. The introduction of the concept of the habitable zone was key to progress in this area. The habitable zone concept was first applied to the space around a star, now called the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable zones have been proposed. We review the historical development of the concept of habitable zones and the present state of the research. We also suggest ways to make progress on each of the habitable zones and to unify them into a single concept encompassing the entire universe.

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“…In the ideal case of exact periods with reasonably even sampling and full time coverage, the error estimates based on the curvature of W RSS(P ) can give good estimates for period errors. But for more complex cases, bootstrap type procedures must be involved (see Jetsu & Pelt 1999). The bootstrap for multichannel methods must take into account the special structure of the input data and will only work if the residuals are uncorrelated.…”

Section: Simple Testsmentioning

confidence: 99%

“…As a rule, astronomers perform time series analysis for each observed channel separately. Sometimes normalization is used to put the channels on an equal footing (see for instance Jetsu & Pelt 1999) and sometimes the results from different channels are averaged (You 1999). It is quite clear that in this way part of the information in the data is lost, especially if the light curves and error estimates for separate channels are substantially different.…”

Section: Introductionmentioning

confidence: 99%

“…The new method described in detail below is a simple and straightforward generalization of the multistage methods (Pelt 1980(Pelt , 1983(Pelt , 1993Jetsu & Pelt 1999). It is based on the phase dispersion minimization method (PDM) at the first (pilot search) stage, a linear model fit (LM) at the second (grid search) stage and finally a nonlinear model fit (NLM) at the last (refined search) stage.…”

Section: Introductionmentioning

confidence: 99%

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Period analysis for simultaneous multichannel photometric observations

You

Pelt

Tuominen

2000

Astron. Astrophys. Suppl. Ser.

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Abstract. The method of three stage weighted period analysis is generalized for simultaneous multichannel observations. The new method is based on the phase dispersion minimization over all channels simultaneously. The three stages in the full algorithm are phase dispersion minimization method (PDM), linear modeling (LM) and nonlinear modeling (NLM). Simple computational tests of the multichannel period analysis (MPA) are presented. We show that the method has advantages if compared with methods where single channels are analysed separately. We derive a general formula for spurious periods and demonstrate that the interpretation of peaks in the PDM spectra can be more complicated than in classical power spectra.

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Three stage period analysis and complementary methods

Cited by 25 publications

References 12 publications

Spot activity of the RS Canum Venaticorum starσGeminorum

Spot activity of the RS Canum Venaticorum starσGeminorum

Habitable Zones in the Universe

Period analysis for simultaneous multichannel photometric observations

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