Flares confirmed for the first time to be from the primary component of an eclipsing binary

Abstract

ABSTRACT Only a handful of precise observations of flare detected from a contact binary so far. This paper presents the photometric and spectroscopic analysis of a contact binary (ASAS J082243+1927.0). Two flare events detected from this object were observed in the data of TESS. The two flare events both occurred at the secondary minimum. Considering the totally eclipsing secondary minimum, it is pretty sure that the two flares are both from the primary component. This is the first time to definitely identify a flare that comes from which component in an eclipsing binary system. This system is a low-mass ratio (q ∼ 0.094) and deep contact binary ($f\sim 69.4~{{\ \rm per\ cent}}$). LAMOST spectra of this object exhibit excess emissions in the H α line, indicating its chromospheric activity. The continuous variation of the TESS light curves is explained by using the variation of a dark spot added to the secondary component. Through analysing the relationship between the variation of the longitude of the spot and the O–C variation of the primary minima, we discover the spot rotation is prograde as viewed in the frame rotating with the orbital motion.