H$\mathsf{_{\alpha}}$ observations of the star FK Com

Kjurkchieva, D.; Marchev, D.

doi:10.1051/0004-6361:20041466

Cited by 13 publications

(16 citation statements)

References 39 publications

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“…Kjurkchieva & Marchev (2005) found that the violet peak of the Hα spectra shows a quasi-sinusoidal change with a maximum at phase 0.75 and a minimum at 0.25. The red peak was at its maximum in Phase 0.25 and at minimum at 0.75, but the changes were not as significant as for the violet one.…”

Section: Correlating Chromospheric and Photospheric Activity Regionsmentioning

confidence: 98%

“…Oliveira & Foing (1999) modelled highly variable Balmer line profiles and confirmed the complex circumstellar structures. Kjurkchieva & Marchev (2005) present highresolution Hα observations spanning over two years. The authors propose a model where FK Com is a binary system with a lowmass secondary star illuminating a circumstellar accretion disk.…”

Section: Introductionmentioning

confidence: 99%

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Study of FK Comae Berenices

Vida

Korhonen

Ilyin

et al. 2015

A&A

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Aims. We study the connection between the chromospheric and photospheric behaviour of the active late-type star FK Comae. Methods. We use spot temperature modelling, light curve inversion based on narrow-and wide-band photometric measurements, Hα observations from 1997−2010, and Doppler maps from 2004−2010 to compare the behaviour of chromospheric and photospheric features. Results. Investigating low-resolution Hα spectra, we find that the changes in the chromosphere seem to happen mainly on a time scale longer than a few hours, but shorter variations are also observed. According to the Hα measurements, prominences are often found in the chromosphere that reach to more than a stellar radius and are stable for weeks, and they seem to be often, but not always connected to dark photospheric spots. The rotational modulation of the Hα emission typically seems to be anticorrelated with the light curve, but we did not find convincing evidence of a clear connection in the long-term trends of the Hα emission and the brightness of the star. In addition, FK Com seems to be in an unusually quiet state in 2009−2010 with very little chromospheric activity and low spot contrast, which might indicate the long-term decrease in activity.

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Section: Correlating Chromospheric and Photospheric Activity Regionsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Study of FK Comae Berenices

Vida

Korhonen

Ilyin

et al. 2015

A&A

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“…The last column lists the extent of the records in years. Single stars are AB Dor, LQ Hya, V410 Tau, and FK Com (about its possible binarity see Kjurkchieva & Marchev 2005), and the rest (V833 Tau, EI Eri, V711 Tau, UZ Lib, UX Ari, HU Vir, IL Hya, XX Tri, HK Lac, and IM Peg) are synchronised, close binaries. In the case of binaries Table 1 gives the orbital period and the rotational period for single stars.…”

Section: The Samplementioning

confidence: 99%

Multiple and changing cycles of active stars

Oláh¹,

Kollath²,

Granzer

et al. 2009

A&A

194

216

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Aims. We study the time variations in the cycles of 20 active stars based on decade-long photometric or spectroscopic observations. Methods. A method of time-frequency analysis, as discussed in a companion paper, is applied to the data. Results. Fifteen stars definitely show multiple cycles, but the records of the rest are too short to verify a timescale for a second cycle. The cycles typically show systematic changes. For three stars, we found two cycles in each of them that are not harmonics and vary in parallel, indicating a common physical mechanism arising from a dynamo construct. The positive relation between the rotational and cycle periods is confirmed for the inhomogeneous set of active stars. Conclusions. Stellar activity cycles are generally multiple and variable.

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“…Recently, Kjurkchieva & Marchev (2005) arrived at the conclusion from three-years of Hα spectroscopy, that the Hα behaviour of FK Com can only be explained if the star is indeed in a binary system with a high mass ratio. Figure 18 in Kjurkchieva & Marchev (2005) shows the binary scenario of FK Com using the same ephemeris as we have used in the present paper.…”

Section: The Possible Effect Of Binaritymentioning

confidence: 99%

Study of FK Comae Berenices

Oláh

Korhonen

Kővári

et al. 2006

A&A

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Aims. Time-series spot modelling was used to follow the longitude changes of active regions responsible for the light variability of FK Com between 1987Com between −2004. Methods. The photometric data are analysed in the time-series mode of a spot modelling code. A scenario of one polar and two low-latitude active regions (hereafter spots, for simplicity) depicts the light variations very well. The role of the polar spot remains unclear because photometry in general does not provide direct latitudinal surface resolution, however, Doppler imaging results of FK Com also show very high latitude or even polar spots besides the low-latitude ones. We also used a light-curve inversion method to confirm some of the results. Results. The two low-latitude spots slowly migrate around 90• and 270• longitudes with quasiperiods of 5.8 and 5.2 years. The spots prefer to stay alternately on one or the other, but on the same hemisphere of the star, with a separation of typically 90−140• . We monitored a flip-flop in the light curve of FK Comae in 1999. The two low-latitude spots, being ≈140−180• from each other during the season, gradually decreased until they both practically vanished. Shortly thereafter, two new spots appeared and started to grow. One of the new spots was near the location of the old one, whereas the other turned up 90• shifted in longitude; consequently, the activity as a whole was shifted to the other hemisphere of the star. We followed a phase jump in 1997, when the two low-latitude spots got closer in longitude and finally merged, or else one of them vanished. A new spot appeared soon, shifted by 100• in longitude, but the activity remained on the same hemisphere. Conclusions. The difference between flip-flops and phase jumps is demonstrated. The derived longitude changes of activity centres may allow us to better constrain the theoretical modelling on the time-behaviour of stellar magnetic activity.

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H$\mathsf{_{\alpha}}$ observations of the star FK Com

Cited by 13 publications

References 39 publications

Study of FK Comae Berenices

Study of FK Comae Berenices

Multiple and changing cycles of active stars

Study of FK Comae Berenices

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