This paper presents a photometric and spectroscopic study of the short-period binary star Cl* Melotte 111 AV 1224 .
Measurements in the B , V , and R passbands obtained during three observing runs between 2014 and 2017 and medium-resolution spectra secured in 2014 , are analyzed together with public data from the SuperWASP and LAMOST projects .
Our light curves show marked asymmetry with a variable O ’ Connell effect .
The SuperWASP photometry is used to derive a mean binary period of 0.345225 days .
The analysis of the ( O - C ) diagram reveals that the orbital period is decreasing at a rate of dP / dt = -3.87 \times 10 ^ { -6 } days yr ^ { -1 } , which may be caused by mass transfer from the more-massive component to the less-massive one .
The system is found to be a single-lined spectroscopic binary with a systemic velocity , \gamma = 1 \pm 3 Km s ^ { -1 } , and a semi-amplitude , K _ { 1 } = 21 \pm 5 Km s ^ { -1 } .
The spectral classification and the effective temperature of the primary component are estimated to be K0V \pm 1 and 5200 \pm 150 K , respectively .
The photometric and spectroscopic solutions reveal that Cl* Melotte 111 AV 1224 is a low-mass ratio ( q = m _ { 2 } / m _ { 1 } \sim 0.11 ) , low-inclination ( \sim~ { } 38 ^ { \circ } ) near-contact system .
The masses , radii and luminosity for the primary and secondary are estimated to be 1.02 \pm 0.06 M _ { \odot } , 1.23 \pm 0.05 R _ { \odot } , 1.01 \pm 0.06 L _ { \odot } and 0.11 \pm 0.08 M _ { \odot } , 0.45 \pm 0.05 R _ { \odot } , 0.10 \pm 0.06 L _ { \odot } , respectively .
The marginal contact , together with the period decrease , suggests that this binary system may be at a key evolutionary stage , as predicted by the theory of thermal relaxation oscillations .