Photometric and spectroscopic observations of GV Leo were performed from 2017 to 2024. The light curves show a flat bottom at the primary eclipse and the conventional O’Connell effect. The echelle spectra reveal that the effective temperature and rotation velocity of the more massive secondary are Teff,2 = 5220 ± 120 K and v2 sin i = 223 ± 40 kms−1, respectively. Our binary modeling indicates that the program target is a W-subclass contact binary with a mass ratio of q = 5.48, an inclination angle of i = 81.◦68, a temperature difference of (Teff,1 − Teff,2) = 154 K, and a filling factor of f = 36%. The light asymmetries were reasonably modeled by a dark starspot on the secondary’s photosphere. Including our 26 minimum epochs, 84 times of minimum light were used to investigate the orbital period of the system. We found that the eclipse times of GV Leo have varied by a sinusoid with a period of 14.9 years and a semi-amplitude of 0.0076 days superimposed on a downward parabola. The periodic modulation is interpreted as a light time effect produced by an unseen outer tertiary with a minimum mass of 0.26 M⊙, while the parabolic component is thought to be a combination of mass transfer (secondary to primary) and angular momentum loss driven by magnetic braking. The circumbinary tertiary would have caused the eclipsing pair of GV Leo to evolve into its current short-period contact state by removing angular momentum from the primordial widish binary.

Introduction
Observations and Data Analysis
    Multiband Photometry
    Echelle Spectra
Binary Modeling and Fundamental Parameters
Eclipse Timing Variation
Summary and Discussion
Acknowledgments
References
List of Eclipse Timings

• Jae Woo Lee(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea) Corresponding author
• Jang-Ho Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Min-Ji Jeong(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Department of Astronomy and Space Science, Chungbuk National University, Cheongju 28644, Republic of Korea)
• Mi-Hwa Song(Department of Astronomy and Space Science, Chungbuk National University, Cheongju 28644, Republic of Korea)
• Chun-Hwey Kim(Department of Astronomy and Space Science, Chungbuk National University, Cheongju 28644, Republic of Korea)