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Cool Spot and Flare Activities of a RS CVn Binary KIC 7885570

Kunt M., Dal H. A.

Acta Astronomica

2017

Vol. 67, No. 4

345--362

We present here the results of our studies on the physical nature and chromospheric activity of a RS CVn binary KIC 7885570 based on the Kepler Mission data. Assuming the primary component temperature, 6530 K, the temperature of the secondary component was found to be 5732±4 K. The mass ratio of the components (q) was found to be 0.43±0.01, while the inclination (i) of the system - 80.6°±0.1°. Additionally, the data were separated into 35 subsets to model the sinusoidal variation due to the rotational modulation, using the SpotModel program, as the light curve analysis indicated the chromospherically active secondary component. It was found that there are generally two spotted areas, whose radii, longitudes and latitudes are rapidly changing, located around the latitudes of +50° and +90° on the active component. Moreover, 113 flares were detected and their parameters were computed from the available data. The One Phase Exponential Association function model was derived from the parameters of these flares. Using the regression calculations, the Plateau value was found to be 1.9815±0.1177, while the half-life value was computed as 3977.2 s. In addition, the flare frequency (N1) - the flare number per hour, was estimated to be 0.00362 h-1, while flare frequency (N2 - the flare-equivalent duration emitted per hour, was computed as 0.00001. Finally, the times of eclipses were computed for 278 minima of the light curves, whose analysis indicated that the chromosphere activity nature of the system causes some effects on these minima times. Comparing the chromospheric activity patterns with the analogues of the secondary component, it is seen that the magnetic activity level is remarkably low. However, it is still at the expected level according to the B-V color index of 0.643 mag for the secondary component.

Catalog of Binary UV Ceti Type Flare Stars

Tamazian V. S., Malkov O. Yu.

Acta Astronomica

2014

Vol. 64, No. 4

359--369

This catalog provides an easy access to the basic astrophysical and dynamical characteristics of nearby (d<25 pc) visual binary systems (pairs) in which at least one component is a UV Cet type flare star. It contains 138 such pairs (111 flare stars) of which 31 pairs have known orbital parameters. Along with parallax mainly (but not only) taken from SIMBAD, apparent and absolute magnitudes of each component, spectral types for all primaries and the vast majority of secondaries are given. On the basis of cataloged data, absolute brightness vs. spectral type and mass vs. spectral type relations for flare and non-flare stars are constructed. It is shown that flare and non-flare stars cannot be distinguished on the absolute brightness vs. spectral type plane. Comparison between photometric and dynamical masses suggests that photometric mass of flare stars can be estimated using the mass vs. absolute brightness relation of non-flare stars.