Abstract
The properties of active regions (cool spots) on the surfaces of 279 G-type stars in which more than 1500 superflares with energies of 1033-1036 erg were detected are analyzed. Diagrams plotting the superflare energy against activity parameters of the stars (the area of their magnetic spots) are considered, and a more extensive study of the activity of two stars with the highest numbers of flares is presented. The range of variation of the superflare energies (up to two orders of magnitude) is realized over the entire interval of rotation periods. It is proposed that the plot of superflare energy vs. rotational period is bimodal. There are probably no appreciable differences in the maximum flare energies for the two groups of objects, which have rotational periods of more than and less than 10 days. Three groups of stars with different surface spottednesses can be distinguished in a plot of superflare energy vs. cool-spot area. The range of variation of the flare energy within a group is roughly the same for these three groups. Most of the points on this diagram lie to the right of the dependence corresponding to B = 3000Gand an inclination i = 90° (the first two groups of objects). It is confirmed that the flare activity is not related directly to circumpolar active regions, since the majority of the points on the diagram lie to the right of the dependence for B = 1000 G and i = 3°. Analysis of stars from the sample, including objects with more than 20 superflares, shows that large variations of the energy (by up to two orders of magnitude) can be reached with small variations of the spottedness parameter S for a single star. Appreciable variability of the spottedness (by factors of five to six) was detected for only two objects from the sample (KIC 10422252 and KIC 11764567). These stars displayed an increase in the flare energy by orders of magnitude for any spottedness level. The activity of KIC 11551430 and KIC 11764567 is analyzed in detail using all available photometric data from the Kepler Space Telescope archives. KIC 11551430 was determined earlier to display the highest number of flares (on average, one flare every 7 days); KIC 11764567 displayed the highest number of flares among stars with rotational periods comparable to the solar period (on average, one flare every 25 days). Maps of surface temperature inhomogeneities of these stars are used to determine the longitudes and other characteristics of their active regions.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
H. Maehara, T. Shibayama, S. Notsu, Yu. Notsu, T. Nagao, S. Kusaba, S. Honda, D. Nogami, and K. Shibata, Nature 485,478(2012).
B. T. Tsurutani, W. D. Gonzales, G. S. Lakhina, and S. Alex, J. Geophys. Res. 108,1268(2003).
I. S. Savanov, Astrophys. Bull. 70,83(2015).
T. Shibayama, H. Maehara, S. Notsu, Yu. Notsu, T. Nagao, S. Honda, T. T. Ishii, D. Nogami, and K. Shibata, Astrophys. J. Suppl. Ser. 209,5(2013).
T. Reinhold, A. Reiners, and G. Basri, Astron. Astrophys. 560, A4 (2013).
I. S. Savanov, Astrofiz. Byull. (2015, in press).
Y. Notsu, T. Shibayama, H. Maehara, Sh. Notsu, T. Nagao, S. Honda, T. T. Ishii, D. Nogami, and K. Shibata, Astrophys. J. 771,127(2013).
R. Wichmann, B. Fuhrmeister, U. Wolter, and E. Nagel, Astron. Astrophys. 567,36(2014).
Ch.-J. Wu, W.-H. Ip, and L.-Ch. Huang, Astrophys. J. 798,92(2015).
I. S. Savanov, Astron. Rep. 55,341(2011).
I. S. Savanov, Astron. Rep. 56,716(2012).
I. S. Savanov and E. S. Dmitrienko, Astron. Rep. 57,757(2013).
I. S. Savanov and E. S. Dmitrienko, Astron. Rep. 56,116(2012).
I. S. Savanov, Astron. Rep. 53,1032(2009).
I. S. Savanov, Astron. Rep. 55,801(2011).
I. S. Savanov and K. G. Strassmeier, Astron. Nachr. 329,364(2008).
Author information
Authors and Affiliations
Corresponding author
Additional information
Original Russian Text © I.S. Savanov, E.S. Dmitrienko, 2015, published in Astronomicheskii Zhurnal, 2015, Vol. 92, No. 9, pp. 758–766.
Rights and permissions
About this article
Cite this article
Savanov, I.S., Dmitrienko, E.S. Activity and cool spots on the surfaces of G-type stars with superflares from observations with the Kepler Space Telescope. Astron. Rep. 59, 879–887 (2015). https://doi.org/10.1134/S1063772915090073
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S1063772915090073