Detailed Chromospheric Activity Nature of KIC 9641031

Monthly Notices of the Royal Astronomical Society

Özdarcan

2017

We present comprehensive spectroscopic and photometric analysis of the detached eclipsing binary KIC 12418816, which is composed of two very similar and young main sequence stars of spectral type K0 on a circular orbit. Combining spectroscopic and photometric modelling, we find masses and radii of the components as 0.88±0.06 M ⊙ and 0.84±0.05 M ⊙ , and 0.85±0.02 R ⊙ , and 0.84±0.02 R ⊙ for the primary and the secondary, respectively. Both components exhibit narrow emission features superposed on the cores of the Ca ii H&K lines, while H α and H β photospheric absoprtion is more completely infilled by broader emission. Very high precision Kepler photometry reveals remarkable sinusoidal light variation at out-of-eclipse phases, indicating strong spot activity, presumably on the surface of the secondary component. Spots on the secondary component appear to migrate towards decreasing orbital phases with a migration period of 0.72±0.05 year. Besides the sinusoidal variation, we detect 81 flares, and find that both components possess flare activity. Our analysis shows that 25 flares among 81 come exhibit very high energies with lower frequency, while the rest of them are very frequent with lower energies.

Section: Discussion and Resultssupporting

confidence: 56%

Section: Discussion and Resultsmentioning

confidence: 99%

High-level magnetic activity nature of the eclipsing binary KIC 12418816

Monthly Notices of the Royal Astronomical Society

Özdarcan

2017

“…This value is 433.10 s for DO Cep ( B − V = 1 m .604), 334.30 s for EQ Peg, and 226.30 s for V1005 Ori (Dal & Evren 2011). In the same way, the half-life parameter is 2291.7 s for KIC 9641031, while it is 1014 s for KIC 9761199, which are binary systems including a dMe-type component (Yoldaş & Dal 2016, 2017). As a result, when the flare total time for the stars such as EQ Peg, V1005 Ori, and DO Cep reaches a few minutes, the their flare energies can easily reach the Plateau level.…”

Section: Resultsmentioning

confidence: 91%

“…The flare frequencies of KOI-256 were compared with the flare frequencies found from the young main-sequence dMe dwarfs, known as UV Ceti-type, exhibiting flare activity. The flare frequencies of KIC 9761199 were found to be N 1 = 0.01351 h −1 and N 2 = 0.00006 (Yoldaş & Dal 2016), while they were found to be N 1 = 0.01735 h −1 and N 2 = 0.00001 for KIC 9641031 (Yoldaş & Dal 2017). KOI-256, when compared to these two systems, seems to have the highest flare frequency values among similar systems.…”

Section: Resultsmentioning

confidence: 94%

“…This value is 3.014 s for EV Lac ( B − V = 1 m .554), 2.935 s for EQ Peg ( B − V = 1 m .574) and 2.637 s for V1005 Ori ( B − V = 1 m .307) (Dal & Evren 2011). The Plateau value was found to be 1.232 ± 0.069 s for KIC 9641031 ( B − V = 0 m .74) (Yoldaş & Dal 2016) and 1.951 ± 0.069 for KIC 9761199 ( B − V = 1 m .303) (Yoldaş & Dal 2017). If it is considered that one of the components is a white dwarf in the case of KOI-256, it is clear in this study that the chromospherical active component is the main-sequence star from the spectral type of M3.…”

Section: Resultsmentioning

confidence: 95%

See 1 more Smart Citation

KOI-256’s Magnetic Activity Under the Influence of the White Dwarf

Yoldaş

Publ. Astron. Soc. Aust.

2017

Self Cite

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 (T d ) 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 P lateau value known as the saturation level of the active component was calculated to be 2.3121±0.0964 s, and the Half − lif e 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 h −1 , 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.

Chromospheric activity behavior of an eclipsing binary system KOI 68AB

Kaya

2019

Astron Nachr

We present the results obtained from KOI 68AB's light variation, which exhibits a sinusoidal light variation due to the stellar spots. Two active regions longitudinally separated by about 180° between the latitudes of +70° and +110° were found. A total of 313 flares were determined, and flare parameters were calculated. The One Phase Exponential Association model was derived using these parameters. The energy saturation parameter Plateau value was found to be 1.219 ± 0.088 s, and its time scale parameter half‐life value was found to be 1,190 s. The flare number per hour, known as N1 frequency, was found to be 0.02406 h−1, while the flare‐equivalent duration emitted per hour, known as N2, was found to be 0.000008. Considering new spectral observations, the target seems to be an eclipsing binary system. Because of this, the light curve is analyzed under an assumption that the target is an eclipsing binary. In these analyses, the sum of the fractional radii is found to be 0.1908, and the fractional radii ratio is 1.8973.