Photometric period and rotational brightness modulation of V833 Tau

Bondar, N. I.

doi:10.1134/s1063772917010024

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…The system is in synchronous rotation, but the photometric rotational period changes slightly due a migration of starspots over the main cycle. The differential rotation appears to be the same as that on the Sun (Olah & Pettersen 1991;Bondar' 2017), but Alekseev (2005) has proposed an anti-solar type of differential rotation.…”

Section: V833 Tau: General Propertiesmentioning

confidence: 86%

Wavelet analysis of the long-term activity of V833 Tau

Stepanov,

Bondar',

Katsova

et al. 2020

Preprint

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The bulk of available stellar activity observations is frequently checked for the manifestation of signs in comparison with the known characteristic of solar magnetic modulation. The problem is that stellar activity records are usually an order of magnitude shorter than available observations of solar activity variation. Therefore, the resolved time scales of stellar activity are insufficient to decide reliably that a cyclic variation for a particular star is similar to the well-known 11-yr sunspot cycles. As a result, recent studies report several stars with double or multiple cycles which serve to challenge the underlying theoretical understanding. This is why a consistent method to separate 'true' cycles from stochastic variations is required. In this paper, we suggest that a conservative method, based on the best practice of wavelet analysis previously applied to the study of solar activity, for studying and interpreting the longest available stellar activity record -photometric monitoring of V833 Tau for more than 100 years. We find that the observed variations of V833 Tau with timescales of 2 -50 yr should be comparable with the known quasi-periodic solar mid-term variations, whereas the true cycle of V833 Tau, if it exists, should be of about a century or even longer. We argue that this conclusion does not contradict the expectations from stellar dynamo theory.

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Section: V833 Tau: General Propertiesmentioning

confidence: 86%

Wavelet analysis of the long-term activity of V833 Tau

Stepanov,

Bondar',

Katsova

et al. 2020

Preprint

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show abstract

“…In this context, observations of the long-term variability of the V833 Tau K-dwarf with saturated activity (Bondar, 2015;2017) are of interest. This star is characterized by a very powerful corona: the coronal activity index log L X /L bol reaches -3.04.…”

Section: Introductionmentioning

confidence: 99%

Long-Term Cyclic Variability of YZ CMi in the Context of Solar and Stellar Physics

Bondar

Katsova

2018

Geomagn. Aeron.

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Manifestations of activity on the YZ CMi (M4.5Ve) flare star which has a rotation period of 2.77 days and belongs to a group of activity-saturated stars, are considered from long-term photometric data together with photographic measurements from 1926 to 2009. Long-term changes in yearly mean brightness of the star are found on a time scale of 27.5 years with an amplitude of 0.2 − 0.3 m that indicate variations in development of surface inhomogeneities and a large degree of surface spottedness in the maximum activity. Spots are distributed unevenly over the surface, their concentration is higher at certain longitudes spaced by intervals equal to 0.6 phases of the rotation period. The recovery of active longitude (a possible "flip-flop" effect) occurs over a period of about 6 years. We note differences in activity of this star from typical for the Sun and solar-like stars, which are associated with its dynamic characteristics P cyc and P rot and its inner structure.

show abstract

Wavelet analysis of the long-term activity of V833 Tau

Stepanov

Bondar

Katsova

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The bulk of available stellar activity observations is frequently checked for the manifestation of signs in comparison with the known characteristic of solar magnetic modulation. The problem is that stellar activity records are usually an order of magnitude shorter than available observations of solar activity variation. Therefore, the resolved time-scales of stellar activity are insufficient to decide reliably that a cyclic variation for a particular star is similar to the well-known 11-yr sunspot cycles. As a result, recent studies report several stars with double or multiple cycles which serve to challenge the underlying theoretical understanding. This is why a consistent method to separate ‘true’ cycles from stochastic variations is required. In this paper, we suggest that a conservative method, based on the best practice of wavelet analysis previously applied to the study of solar activity, for studying and interpreting the longest available stellar activity record – photometric monitoring of V833 Tau for more than 100 yr. We find that the observed variations of V833 Tau with time-scales of 2–50 yr should be comparable with the known quasi-periodic solar mid-term variations, whereas the true cycle of V833 Tau, if it exists, should be of about a century or even longer. We argue that this conclusion does not contradict the expectations from the stellar dynamo theory.

show abstract

Photometric period and rotational brightness modulation of V833 Tau

Cited by 3 publications

References 11 publications

Wavelet analysis of the long-term activity of V833 Tau

Wavelet analysis of the long-term activity of V833 Tau

Long-Term Cyclic Variability of YZ CMi in the Context of Solar and Stellar Physics

Wavelet analysis of the long-term activity of V833 Tau

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