Chromospheric activity behavior of an eclipsing binary system KOI 68AB

Abstract

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.

Some findings from the longitudinal migration of starspots

“…out-of-eclipse phases, for which synthetic light curves were needed. In the case of KIC 8669092, one of the remaining five systems, the light curve analysis was recently done by Kaya & Dal (2019). We used the synthetic curve they derived to obtain the variations seen at out-of-eclipse phases of this system.…”

“…Shibayama et al (2013) detected four flares from the observation data of KIC 4357272, while Gao et al (2016) found 58 flares from the same data. Balona (2015), Gao et al (2016), and Kaya & Dal (2019), who analysed the light variations of KIC 8669092, known as KOI 68AB, stated that the target is a binary system with an active chromospheric component. Also, Kaya & Dal (2019) detected 313 flares exhibited by the active component of KOI 68AB during an observation period of approximately 4 years.…”

“…Balona (2015), Gao et al (2016), and Kaya & Dal (2019), who analysed the light variations of KIC 8669092, known as KOI 68AB, stated that the target is a binary system with an active chromospheric component. Also, Kaya & Dal (2019) detected 313 flares exhibited by the active component of KOI 68AB during an observation period of approximately 4 years. Furthermore, they observed the longitudinal and latitudinal movement of the twospotted areas on the surface of the active component.…”

Soğuk Yıldız Lekelerinin Boylamsal Göç Hareketinde Görünen Salınımlar

“…Tutulma dışındaki sinüzoidal değişimleri ortaya çıkarmak için, 4 hedef sistemin ışık eğrisi analizi yapılmıştır. Kalan 6 sistemden biri olan KIC 08669092 için ışık eğrisi analizi, Kaya & Dal (2019) tarafından yapılmıştır. Bu sistemin tutulma dışındaki değişimlerini elde etmek için ışık eğrisi analizinden elde ettikleri kuramsal eğri kullanılmıştır.…”

Stellar Chromospheric Variability

“…Finally, magnetically active stars tend to exhibit flares or superflares (sudden releases of magnetic energy) [49], often large and rapidly evolving starspots (cooler regions where convection is suppressed by strong magnetic fields) [50][51][52][53][54], as well as faculae and plages (unusually bright regions in the photosphere and chromosphere, respectively) [8,55]. Dark starspots and bright faculae are usually located in stellar photospheres, whereas plages tend to be associated with chromospheres [55].…”