Spectroscopic Disentangling Revealed the Tertiary Component in the Multiple System EMBoo

We present a comprehensive photometric and spectroscopic study of the triple stellar system EMBoo. The system is composed ofdetached, low-mass components, and for the first time in the literature, the spectrum of the tertiary component has been successfullydisentangled from the composite spectrum using the KOREL code. Synthetic spectra were generated for each disentangledcomponent, allowing determination of their atmospheric parameters. The depth of the H𝛼 line in the tertiary spectrum indicatesthat it is an intermediate-temperature star, consistent with spectral types between A and F, and its effective temperature wasdetermined to be 7000 K. By analyzing the radial velocity and light curves simultaneously, the fundamental physical parameters ofthe system were derived, and its detailed evolutionary status was investigated using MESA models. The HIPPARCOS trigonometricparallax (𝜛Hip = 1.33 ± 1.45 mas) and Gaia DR3 trigonometric parallax (𝜛Gaia = 3.9699 ± 0.1812 mas) show a significantdiscrepancy, most likely related to the system’s multiplicity and the limitations of single-star astrometric solutions. To provideindependent distance estimates, we modeled the spectral energy distribution (SED) using multi-wavelength flux data, yielding𝐸(𝐵 − 𝑉) = 0.05 mag and a trigonometric parallax 𝜛SED = 3.2 mas, corresponding to 𝑑SED = 313 pc. Furthermore, photometricdistance estimates based on the components’ absolute magnitudes yield 𝑑1 = 299 pc and 𝑑2 = 301 pc, in good agreement withthe SED-based distance. Both the SED-based and photometric distances converge around 𝑑 = 300 pc, indicating that the Gaiatrigonometric parallax underestimates the true distance of EMBoo.Keywords: EM Boo system – Eclipsing binary stars – Stellar fundamental parameters – Spectroscopy – Photometry