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Description
We present a detailed period analysis of TY Bootis, based on all available light minimum times covering about 80 years. We discovered that there exists a cyclic variation overlaying a secular period decrease from the distorted (O-C) diagram. A long-term decrease with a sinusoidal oscillation (i.e., eq. (2)) or with a light-time effect (i.e., eq. (3)) may be reasonable due to the smaller difference between their sum of residuals. The sinusoidal change with a period of 59.7 yr for equation (2) can be attributed to either a light-time effect or cyclic magnetic activity of both components. For the assumed third body, the period and eccentricity of the light-time orbit are P_3_=58.6yr and e'=0.1744, respectively. If the existence of an additional unseen body is true, this binary may be a tertiary system. The long-term orbital period decrease suggests that TY Boo is undergoing a mass transfer from the primary component to the secondary component at a rate of dm/dt=-3.15x10^-8^M_{sun}_/yr for equation (2) or dm/dt=-2.90x10^-8^M_{sun}_/yr for equation (3). As its mass transfers, accompanied by angular momentum loss due to mass outflow L_2_, this binary will evolve into a deep contact configuration.
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