ET Dra activity according to observations in 2018–2023

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Resumo

The results of new photometric observations of the chromospherically active star ET Dra, performed using telescopes of the Zvenigorod INASAN Observatory, the Russian-Cuban Observatory in the territory of the Republic of Cuba (Havana) and the Terskol INASAN Observatory (a total of 8 sets of observations), as well as the addition of archival observations of the Kamogata Wide-field Survey. According to the data received during 2018–2023 changes in the shape of the light curve caused by the rotational modulation of a star with spots on the surface, as well as studies of the long-term variability of the star’s brightness were investigated. Characteristic changes in the ET Dra light curve are noted including a decrease of the stellar brightness in V filter, its cyclic changes and subsequent brightness increase. The shape of the phase curve and the duration of the extended minimum of brightness vary. During the HJD 245 9670 – 245 9715 interval the amplitude of the star’s brightness variability reached a maximum value of more than 0.4 magnitude, as it was in 1990. For each of the 8 set of observations the surface temperature inhomogeneities map were calculated and estimates of the spotedness parameter S of the object were performed. Maximum value of parameter S was 32.2–33.5%. Based on the constructed power spectra the values of possible cycles of long-term activity of the star are obtained as 570 and 1160 days (1.56 and 3.18 years).

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Sobre autores

I. Savanov

Institute of Astronomy of the Russian Academy of Sciences

Autor responsável pela correspondência
Email: igs231@mail.ru
Rússia, Moscow

S. Naroenkov

Institute of Astronomy of the Russian Academy of Sciences

Email: igs231@mail.ru
Rússia, Moscow

M. Nalivkin

Institute of Astronomy of the Russian Academy of Sciences

Email: igs231@mail.ru
Rússia, Moscow

A. Tarasenkov

Institute of Astronomy of the Russian Academy of Sciences

Email: igs231@mail.ru
Rússia, Moscow

E. Dmitrienko

Lomonosov Moscow State University, Sternberg Astronomical Institute

Email: igs231@mail.ru
Rússia, Moscow

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Ação
1. JATS XML
2. Fig. 1. Top: observed V-band light curves of ET Dra based on SAO RAS Mini-Mega TORTORA observations (corrected for the long-term trend) (filled circles), Kamogata Wide-field Survey (KWS) data (crosses), and observations from sets 1–8 (open circles). The abscissa shows time in the HJD 240 0000 + t format. Middle panel: light curve based on our observations in the HJD 245 9670 – 245 9750 interval. The abscissa shows time also in the HJD 240 0000 + t format. Bottom: power spectrum in the period interval from 0 to 6000 days. Vertical lines correspond to cycles of 570, 1160, and 3600 d (see text).

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3. Fig. 2. Results of reconstructing temperature inhomogeneities on the surface of ET Dra. For each set, the following are shown: on the left — maps of the star's surface based on observations in sets 1–8 (presented on a single scale, darker areas in the figures correspond to higher values of the filling factors f). The abscissa axis shows longitude in degrees, and the ordinate axis shows latitude in degrees. On the right — observed light curves (crosses) and theoretical curves constructed using the reconstructed model. The set number is shown above each light curve.

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