Abstract
We report the results of a study of spot activity manifestations in 11 K-type dwarfs with established planets in the habitable zone according to the data from the Kepler space telescope archive acquired during 90-day long Q3-set observations. We found that the spot area \(A\) on the surface of K-type dwarfs of our list is greater than the characteristic solar value, but is comparable to the maximum levels observed for the Sun, except for the active star KIC 9351316 with \(A=7588\) MSH. We performed a detailed study of the K-type dwarf KIC 5938970 (Kepler-1540) with flare activity higher than that of the Sun and flare energy \(\log E\) spanning the 32.95–34.48 interval. We estimated the rotation period of the star, \(P=15\overset{\textrm{d}}{.}1447\), and its parameter \(\Delta\Omega=0.024\pm 0.007\) rad/day. Based on the Kamogata Wide-field Survey data (99 \(V\)-band magnitude estimates in 3310 days) we conclude that photometric variations include cyclic changes and a weak monotonic brightness increase. The characteristic periods of possible cycles are equal to 2.8 and 4.4 years. Our study of the star’s activity in about half of the currently known K-type dwarfs with planets in the habitable zone (11 objects among 17 stars in the complete list) based on high-precision observations made with the Kepler telescope revealed certain activity manifestations (high flare activity in one star, high spot activity in another, etc.). We conclude that a detailed study of activity manifestations in each particular star is highly desirable when studying planetary systems of K-type stars including planets in the habitable zone.
Notes
kws.cetus-net.org
REFERENCES
M. L. Hill, K. Bott, P. A. Dalba, et al., Astron. J. 165 (2), id. 34 (2023).
J. Lillo-Box, N. C. Santos, A. Santerne, et al., Astron. and Astrophys. 667, id. A102 (2022).
H. Maehara, J. Space Sci. Informatics Japan, 3, 119 (2014).
T. Reinhold, A. Reiners, and G. Basri, Astron. and Astrophys. 560, id. A4 (2013).
I. S. Savanov, Astrophysical Bulletin 70 (1), 83 (2015).
I. S. Savanov, Astronomy Reports 62 (11), 814 (2018).
I. S. Savanov, Astrophysics 65 (3), 361 (2022).
I. S. Savanov, Astrophysics 66 (2023) (accepted).
H. Yang and J. Liu, Astrophys. J. Suppl. 241 (2), article id. 29 (2019).
ACKNOWLEDGMENTS
This research made use of the data provided by SIMBAD astronomical database and archives of the Kepler space mission and Kamogata Wide-field Survey.
Funding
This study was carried out within the framework of the project ‘‘Study of stars with exoplanets’’ funded by a grant from the Government of the Russian Federation for supporting investigations headed by leading researchers (Agreement No. 075-15-2019-1875 and No. 075-15-2022-1109).
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
The authors declare that there is no conflict of interest.
Additional information
Translated by A. Dambis
Rights and permissions
About this article
Cite this article
Savanov, I.S. Analysis of the Activity of 11 K-type Dwarfs with Planets in the Habitable Zone. Astrophys. Bull. 78, 200–208 (2023). https://doi.org/10.1134/S1990341323020086
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S1990341323020086