Long-term variations in the spottedness of BY Dra M dwarfs
- 21 Downloads
The results of a spottedness study for twelve red dwarf stars covering several decades and based on a vast amount of photometric observations are presented. The analysis makes use of multicolor (UBV RI) photometric monitoring of ten of these stars since 1991 at the Crimean Astrophysical Observatory, as well as data from the literature. The spottedness parameters for selected active BY Dra red dwarfs have been refined using an improved zonal model for the spotted stellar atmospheres to allow for the possible presence of two active longitudes on the stars. Time variations in the spot activity of these systems are analyzed in order to look for possible cycles. Three of the stars show a drift of their spots in the latitude towards the stellar poles; however, the magnitude of this latitude drift is a factor of two to three lower than the analogous value for sunspots. All the stars except for YZ CMi display relationships between the area of the spots and their latitude, with correlation coefficients R from 0.67 to 0.97. Evidence for the presence of activity cycles with durations from 25 to 40 years is found for six stars, which are characterized by synchronous variations in the areas and latitudes of their spots, as well as of the overall photometric brightness.
Unable to display preview. Download preview PDF.
- 3.I. Yu. Alekseev, Low Mass Spotted Stars (Astro-Print, Odessa, 2001) [in Russian].Google Scholar
- 4.R. E. Gershberg, Solar-Type Activity of Main Sequence Stars, Astronomy and Astrophysics Library (Springer, Berlin, Heidelberg, 2005; Antikva, Simferopol’, 2015).Google Scholar
- 8.B. R. Pettersen, Inst. Theor. Astrophys. Blindern. Oslo Rep. 46 (1976).Google Scholar
- 9.V. Piirola, Observ. Astrophys. Lab. Univ. Helsinki Rep. 6, 151 (1984).Google Scholar
- 11.I. Yu. Alekseev, Bull. Crimean Astrophys. Observatory 104, 272 (2008).Google Scholar
- 12.I. Yu. Alekseev, Doctoral (Phys. Math.) Dissertation (2016).Google Scholar
- 16.F. M. Mahmoud and K. Olah, Inform. Bull. Var. Stars 1943 (1981).Google Scholar
- 17.I. Yu. Alekseev and R. E. Gershberg, in The Earth and the Universe, Ed. by G. Asteriadis, A. Bantelas, M. E. Contadakis, et al. (Univ. of Thessaloniki, Greece, 1997), p.43.Google Scholar
- 20.I. C. Busko, C. A.O. Torres, and G. R. Quast, Inform. Bull. Var. Stars 1898 (1980).Google Scholar
- 21.P. J. Amado, Ph.D. Thesis (Univ. Belfast, UK, 1997).Google Scholar