Spectroscopic Disentangling Revealed the Tertiary Component in the Multiple System EM Boo

We present a comprehensive photometric and spectroscopic study of the triple stellar system EM,Boo. The system is composed of detached, low-mass components, and for the first time in the literature, the spectrum of the tertiary component has been successfully disentangled from the composite spectrum using the $\mathtt{\text{KOREL}}$ code. Synthetic spectra were generated for each disentangled component, allowing determination of their atmospheric parameters. The depth of the H${}_{\alpha }$ line in the tertiary spectrum indicates that it is an intermediate-temperature star, consistent with spectral types between A and F, and its effective temperature was determined to be 7000~K. By analyzing the radial velocity and light curves simultaneously, the fundamental physical parameters of the system were derived, and its detailed evolutionary status was investigated using $\mathtt{\text{MESA}}$ models. The $\mathit{\text{HIPPARCOS}}$ trigonometric parallax (${\varpi }_{\mathrm{H}\mathrm{i}\mathrm{p}}=1.33\pm 1.45$ mas) and $\mathit{\text{Gaia}}$ DR3 trigonometric parallax (${\varpi }_{\mathrm{G}\mathrm{a}\mathrm{i}\mathrm{a}}=3.9699\pm 0.1812$ mas) show a significant discrepancy, most likely related to the system’s multiplicity and the limitations of single-star astrometric solutions. To provide independent distance estimates, we modeled the spectral energy distribution (SED) using multi-wavelength flux data, yielding $E(B-V)=0.05$ mag and a trigonometric parallax ${\varpi }_{\mathrm{S}\mathrm{E}\mathrm{D}}=3.2$ mas, corresponding to $d_{\mathrm{S}\mathrm{E}\mathrm{D}}=313$ pc. Furthermore, photometric distance estimates based on the components’ absolute magnitudes yield $d_1=299$ pc and $d_2=301$ pc, in good agreement with the SED-based distance. Both the SED-based and photometric distances converge around $d=300$ pc, indicating that the $\mathit{\text{Gaia}}$ trigonometric parallax underestimates the true distance of EM,Boo.