Periodicity in some light curves of the solar analogue V352 Canis Majoris

Kajatkari, P.; Jetsu, L.; Cole, Elizabeth; Hackman, T.; Henry, Gregory W.; Joutsiniemi, Sirkka‐Liisa; Lehtinen, Jaakko; Mäkelä, Valtteri; Porceddu, Sebastian; Ryynänen, K.; Solea, V.

doi:10.1051/0004-6361/201322847

Cited by 4 publications

(12 citation statements)

References 48 publications

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“…It is also similar to the dataset lengths we have used previously in other studies using the CPS (e.g. Lehtinen et al 2011Lehtinen et al , 2012Kajatkari et al 2015). Figure 3 shows as an example what the differential photometry looks like for HD 171488.…”

Section: Time Series Analysis Of the Photometrysupporting

confidence: 59%

“…In our previous study of the V-band photometry of this star (Kajatkari et al 2015) we were able to detect periodicity in 192 of the 370 datasets with reliable model fits. Here, with two more years of data, we found periodicity in 229 of the 407 reliable datasets from the V-band photometry.…”

Section: Time Series Analysis Of the Photometrymentioning

confidence: 78%

“…We also discarded all datasets having n data < 12 data points because their fits are likely to have low quality. As opposed to previous studies using the CPS method (Lehtinen et al 2011(Lehtinen et al , 2012Hackman et al 2011Hackman et al , 2013Kajatkari et al 2014Kajatkari et al , 2015, we chose to use both the B and V bands in this study to get more data points for the periodic fits and to increase their precision. As can be seen in Fig.…”

Section: Time Series Analysis Of the Photometrymentioning

confidence: 99%

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Activity trends in young solar-type stars

Lehtinen

Jetsu

Hackman

et al. 2016

A&A

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138

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Aims. We study a sample of 21 young and active solar-type stars with spectral types ranging from late F to mid K and characterize the behaviour of their activity. Methods. We apply the continuous period search (CPS) time series analysis method on Johnson B-and V-band photometry of the sample stars, collected over a period of 16 to 27 years. Using the CPS method, we estimate the surface differential rotation and determine the existence and behaviour of active longitudes and activity cycles on the stars. We supplement the time series results by calculating new log R HK = log F HK /σT 4 eff emission indices for the stars from high resolution spectroscopy.Results. The measurements of the photometric rotation period variations reveal a positive correlation between the relative differential rotation coefficient and the rotation period as k ∝ P 1.36 rot , but do not reveal any dependence of the differential rotation on the effective temperature of the stars. Secondary period searches reveal activity cycles in 18 of the stars and temporary or persistent active longitudes in 11 of them. The activity cycles fall into specific activity branches when examined in the log P rot /P cyc vs. log Ro −1 , where Ro −1 = 2Ωτ c , or log P rot /P cyc vs. log R HK diagram. We find a new split into sub-branches within this diagram, indicating multiple simultaneously present cycle modes. Active longitudes appear to be present only on the more active stars. There is a sharp break at approximately log R HK = −4.46 separating the less active stars with long-term axisymmetric spot distributions from the more active ones with non-axisymmetric configurations. In seven out of eleven of our stars with clearly detected long-term non-axisymmetric spot activity the estimated active longitude periods are significantly shorter than the mean photometric rotation periods. This systematic trend can be interpreted either as a sign of the active longitudes being sustained from a deeper level in the stellar interior than the individual spots or as azimuthal dynamo waves exhibiting prograde propagation.

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Section: Time Series Analysis Of the Photometrysupporting

confidence: 59%

Section: Time Series Analysis Of the Photometrymentioning

confidence: 78%

Section: Time Series Analysis Of the Photometrymentioning

confidence: 99%

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Activity trends in young solar-type stars

Lehtinen

Jetsu

Hackman

et al. 2016

A&A

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138

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“…The time spans of these slices are T 586 D = days (Figure 30 . This is an excellent result, considering that the CPS method, or the power spectrum method, can only model data sets having a time span of T 30 D = days or less (e.g., Kajatkari et al 2015). The main advantage of our model of Equation (9) is that it can adjust to changes of the amplitude and the shape of the light curve.…”

Section: Discussionmentioning

confidence: 95%

General Model for Light Curves of Chromospherically Active Binary Stars^∗

Jetsu

Henry

Lehtinen

2017

ApJ

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The starspots on the surface of many chromospherically active binary stars concentrate on long-lived active longitudes separated by 180°. Shifts in activity between these two longitudes, the "flip-flop"events, have been observed in single stars like FK Comae and binary stars like σ Geminorum. Recently, interferometry has revealed that ellipticity may at least partly explain the flip-flop events in σ Geminorum. This idea was supported by the double-peaked shape of the long-term mean light curve of this star. Here we show that the long-term mean light curves of 14 chromospherically active binaries follow a general model that explains the connection between orbital motion, changes in starspot distribution, ellipticity, and flip-flop events. Surface differential rotation is probably weak in these stars, because the interference of two constant period waves may explain the observed light curve changes. These two constant periods are the active longitude period P act ( ) and the orbital period P orb ( ). We also show how to apply the same model to single stars, where only the value of P act is known. Finally, we present a tentative interference hypothesis about the origin of magnetic fields in all spectral types of stars.

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“…We analyzed the original V magnitudes of BM CVn with the CPS method formulated by Lehtinen et al (). This method is described here only briefly, because we have already applied it to the photometry of numerous stars (Hackman et al, (), (); Lehtinen et al, (); Lehtinen, Jetsu, Hackman, Kajatkari, & Henry, (), (); Kajatkari, Hackman, Jetsu, Lehtinen, & Henry, (), Kajatkari et al, ()). We divided the observations into datasets having a maximum length of Δ T max =1.5 P orb =30.…”

Section: Cps Methodsmentioning

confidence: 99%

Time‐series analysis of long‐term photometry of BM Canum Venaticorum

et al. 2017

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† The analyzed photometry and numerical results of the analysis are both published electronically at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/yyy/ Axxx.Long-term photometry is commonly used to monitor chromospheric activity of late-type stars. We study standard Johnson differential V photometry of the RS CVn binary BM Canum Venaticorum (BM CVn) spanning over a quarter of a century. Our main aims are to determine the activity cycles, the rate of surface differential rotation, and the rotation period of the active longitudes of BM CVn. The continuous period search (CPS) algorithm is applied to the photometry. The changes of the mean and amplitude of the light curves are used to search for activity cycles. The rotation period changes give an estimate of the rate of surface differential rotation. The Kuiper method is applied to the epochs of the primary and secondary minima to search for active longitudes. The photometry reveals the presence of a stable mean light curve (MLC) connected to the orbital period P orb = 20. d 6252 of this binary. We remove this MLC from the original V magnitudes, which gives us the corrected V ′ magnitudes. These two samples of V and V ′ data are analyzed separately with CPS. The fraction of unreliable CPS models decreases when the MLC is removed. The same significant activity cycle of approximately 12.5 years is detected in both V and V ′ samples. The estimate for the surface differential rotation coefficient, k ≥ 0.10, is the same for both samples, but the number of unrealistic period estimates decreases after removing the MLC. The same active longitude period of P al = 20. d 511 ± 0. d 005 is detected in the V and V ′ magnitudes. This long-term regularity in the epochs of primary and secondary minima of the light curves is not caused by the MLC. On the contrary, the MLC hampers the detection of active longitudes.

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Periodicity in some light curves of the solar analogue V352 Canis Majoris

Cited by 4 publications

References 48 publications

Activity trends in young solar-type stars

Activity trends in young solar-type stars

General Model for Light Curves of Chromospherically Active Binary Stars^∗

Time‐series analysis of long‐term photometry of BM Canum Venaticorum

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Periodicity in some light curves of the solar analogue V352 Canis Majoris

Cited by 4 publications

References 48 publications

Activity trends in young solar-type stars

Activity trends in young solar-type stars

General Model for Light Curves of Chromospherically Active Binary Stars∗

Time‐series analysis of long‐term photometry of BM Canum Venaticorum

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Product

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General Model for Light Curves of Chromospherically Active Binary Stars^∗