KOI-256's Magnetic Activity under the Influence of the White Dwarf

TL;DR

This study analyzes KOI-256's chromospheric activity, revealing sinusoidal variations from cool spots, detailed flare characteristics, and phase-dependent flare occurrence influenced by the white dwarf companion.

Contribution

It provides the first detailed analysis of KOI-256's magnetic activity, combining spot modeling and flare statistics with phase-dependent flare behavior due to the white dwarf.

Findings

Active regions exhibit migration periods of 3.95 and 8.37 years.

225 flares detected with specific parameters calculated.

Flares tend to occur at particular phases influenced by the white dwarf.

Abstract

We present the findings about chromospheric activity nature of KOI-256 obtained from the Kepler Mission data. Firstly, it was found that there are some sinusoidal variations out-of-eclipses due to cool spot activity. The sinusoidal variations modelled by the SPOTMODEL program indicate that the active component has two different active regions. Their longitudinal variation revealed that one of them has a migration period of 3.95 years, while the other has a migration period of 8.37 years. Secondly, 225 flares were detected from the short cadence data in total. The parameters, such as increase (Tr) and decay (Td) times, total flare time (Tt), equivalent durations (P), were calculated for each flare. The distribution of equivalent durations versus total flare times in logarithmic scale is modelled to find flare activity level. The Plateau value known as the saturation level of the active component was calculated to be 2.3121+-0.0964 s, and the Half-life value, which is required flare total time to reach the saturation, was computed to be 2233.6 s. In addition, the frequency of N1, which is the number of flares per an hour in the system, was found to be 0.05087 1/h, while the flare frequency N2 that the flare-equivalent duration emitting per an hour was found to be 0.00051. Contrary to the spot activity, it has been found that the flares are in tends to appear at specific phases due to the white dwarf component.