WASP 0346-21: An EL CVn-Type Eclipsing Binary with Multiperiodic Pulsations in a Triple System

VLT/UVES spectroscopic and TESS photometric observations for WASP 0346-21 allow the direct determination of its physical properties, along with the detection of a circumbinary object and oscillating signals. The high-resolution spectra yielded the radial velocities of all three stars and the atmospheric parameters of T ₄₅₅, ₀ = 722542 K, M/H = 0. 300. 03 dex, and v ₀ i = 785 km s^-1 of the primary component. The combined analysis of these observations resulted in the fundamental parameters of the eclipsing components and the third light of l₃ = 0. 0430. 004, which is consistent with the light contribution of the tertiary star observed in the echelle spectra. WASP 0346-21 A resides within the overlapping main-sequence domain of Sct and Dor variables, while the secondary component of M ₁ = 0. 1850. 013 M_, R ₁ = 0. 3080. 023 R_, T ₄₅₅, ₁ = 10, 655146 K, and L ₁ = 1. 090. 17 L_ matches well with the low-mass white dwarf (WD) model for Z = 0. 01, corresponding to the thick-disk population classified by the Galactic kinematics. Multifrequency analyses were performed on the residual TESS data after removing the binarity effects. The low frequencies around 26. 348 day^-1 and 17. 683 day^-1 are Sct pulsations originating from WASP 0346-21 A, and the high frequencies of 97. 996 day^-1 and 90. 460 day^-1 are considered to be extremely low-mass WD oscillations. These results demonstrate that WASP 0346-21 is a hierarchical triple system, consisting of an EL CVn binary with multiperiodic pulsations in each component and a distant outer tertiary.