Broad-band multicolor photometry and polarimetry of spotted stars

Alekseev, I. Yu.

doi:10.1134/1.1575857

Cited by 14 publications

(21 citation statements)

References 35 publications

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“…On the other hand, the photometric study of Alekseev (2003) indicates that spots may even be 2200 K cooler than the photosphere, a result that is quite similar to the one by O'Neal et al (2004) based on TiO-band observations. Our maps (Fig.…”

Section: Temperature Mapssupporting

confidence: 83%

EK Draconis

Järvinen

Berdyugina

Korhonen

et al. 2007

A&A

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Context. As a young solar analogue, EK Draconis provides an opportunity to study the magnetic activity of the infant Sun. Aims. We present three new surface temperature maps of EK Draconis and compare them with previous results obtained from longterm photometry. Furthermore, we determined a set of stellar parameters and compared the determined values with the corresponding solar values. Methods. Atmospheric parameters were determined by comparing observed and synthetic spectra calculated with stellar atmosphere models. Surface temperature maps were obtained using the Occamian approach inversion technique. The differential rotation of EK Dra was estimated using two different methods. Results. A detailed model atmosphere analysis of high resolution spectra of EK Dra has yielded a self-consistent set of atmospheric parameters: T eff = 5750 K, log g = 4.5, [M/H] = 0.0, ξ t = 1.6 km s −1 . The evolutionary models imply that the star is slightly more massive than the Sun and has an age between 30−50 Myr, which agrees with the determined lithium abundance of log N(Li) = 3.02.Moreover, the atmospheric parameters, as well as the wings of the Ca ii 8662 Å, indicate that the photosphere of EK Dra is very similar to the one of the present Sun, while their chromospheres differ. There also seems to be a correlation between magnetic features seen in the photosphere and chromosphere. The temperature images reveal spots of only 500 K cooler than the quiet photosphere. The mean spot latitude varies with time. The obtained differential rotation is very small, but the sign of it supports solar type differential rotation on EK Dra.

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Section: Temperature Mapssupporting

confidence: 83%

EK Draconis

Järvinen

Berdyugina

Korhonen

et al. 2007

A&A

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“…The Doppler imaging study by Strassmeier & Rice (1998) recovered a spot temperature in 1995 of ∆T ≈ 1200 K from 12 major spectral lines. The photometric study of Alekseev (2003) indicated that spots may even be 2200 K cooler than the photosphere, a result that is quite similar to the result of O'Neil et al (2004) based on TiO-band observations. Because we were interested only in spot longitudes, possible errors in the temperature values were not important.…”

Section: Light Curve Inversionssupporting

confidence: 76%

Spots on EK Draconis

Järvinen

Berdyugina

Strassmeier

2005

A&A

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Abstract.We analyse photometric observations of the young active star EK Dra, altogether about 21 years. Similar to the ZAMS stars LQ Hya and AB Dor, EK Dra shows long-lived, non-axisymmetric spot distribution with active longitudes on opposite hemispheres. At least two activity cycle can be found from the data. The first cycle originates from repeated switches of the activity between two active longitudes in about (2-2.25)-year intervals, resulting in a cycle of about (4-4.5) years. The second cycle is of the order of 10.5 years and comes from migration of the active longitudes. Our data cover two consecutive cycles. The periodicity is also present in the maximum, the mean and the minimum stellar brightness. Additionally, there is a long-term trend. If we combine our data with the Sonneberg plate measurements, we can conclude that the overall brightness of EK Dra has been continuously decreasing at least for the last 45 years. A comparison with current sunspot activity reveals many similarities between the Sun and EK Dra.

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“…And so we conclude that phase coverage for the temperature maps in this report is sufficient for drawing some basic conclusions, with 50% or better phase coverage for all seasons (see Table 1). The total observations cover just over 4 years, which is a few years shy of the oft-cited cycle of about 6-7 years (e.g., Jetsu 1993;Cutispoto 1998a;Alekseev 2003).…”

Section: Observationsmentioning

confidence: 99%

Doppler imaging of LQ Hydrae for 1998–2002

Cole

Hackman

Käpylä

et al. 2015

A&A

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Aims. We study the spot distribution on the surface of LQ Hya during the observing seasons October 1998-November 2002. We look for persistent active longitudes, trends in the level of spot activity and compare to photometric data. Methods. We apply the Doppler imaging technique on photospheric spectral lines using an inversion code to retrieve images of the surface temperature.Results. We present new temperature maps using multiple spectral lines for a total of 7 seasons. Conclusions. We find no evidence for active longitudes persisting over multiple observing seasons. The spot activity appears to be concentrated to two latitude regions. Using the currently accepted rotation period, we find spot structures to show a trend in the phase-time plot, indicative of a need for a longer period. We conclude that the long-term activity of LQ Hya is more chaotic than that of some magnetically active binary stars analyzed with similar methods, but still with clear indications of an activity cycle from the photometry.

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Broad-band multicolor photometry and polarimetry of spotted stars

Cited by 14 publications

References 35 publications

EK Draconis

EK Draconis

Spots on EK Draconis

Doppler imaging of LQ Hydrae for 1998–2002

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