Apsidal Motion and Physical Parameters of V361 Cam

Our multicolour photometric measurements of V361 Cam (\(P{{ = 8.64}^{d}}\), \(V{{ = 10.79}^{m}}\), \(e = 0.12\), B5 IV + B9 V) over the past 16 years, as well as TESS data, allowed us to determine for the first time the main physical characteristics of the system and measure the apsidal rotation velocity. The following physical parameters of the component stars were obtained: \({{T}_{1}} = 15{\kern 1pt} {\kern 1pt} 400 \pm 300\) K, \({{M}_{1}} = 6.0 \pm 0.4{\kern 1pt} {{M}_{ \odot }}\), R₁ = 5.03 ± \(0.05{\kern 1pt} {{R}_{ \odot }}\), \({{T}_{2}} = 11{\kern 1pt} {\kern 1pt} 700 \pm 250\) K, \({{M}_{2}} = 2.8 \pm 0.2{\kern 1pt} {{M}_{ \odot }}\), \({{R}_{2}} = 1.94 \pm 0.04{\kern 1pt} {{R}_{ \odot }}\). The photometric parallax of 0.00035″ ± \(0.000001^{''} \) matches the Gaia measurement of \(0.00035^{''} \pm 0.00003^{''} \). The apsidal rotation velocity is \({{\dot {\omega }}_{{{\text{obs}}}}} = 0.024 \pm 0.007\)°/year, which is less than the theoretical value under the synchronism condition \({{\dot {\omega }}_{{{\text{theor}}}}} = 0.056 \pm 0.006\)°/year. The age of the system, assuming solar chemical composition, is 70 Myr. Both components are pulsating \(\beta \) Cephei variables.