FX UMa: A New Heartbeat Binary System with Linear and Nonlinear Tidal Oscillations and δ Sct Pulsations

Abstract

We present a detailed analysis of an eclipsing double-lined binary FX UMa based on TESS photometry and newly acquired spectroscopic observations. The radial velocities and atmospheric parameters for each component star are obtained from the SONG high-resolution spectra. Combined with the radial-velocity measurements, our light-curve modeling yields absolute masses and radii of the two components. The Fourier amplitude spectrum of the residual light curve reveals a total of 103 frequencies with signal-to-noise ratio (S/N) ≥ 4, including 12 independent frequencies, 17 multiples of the orbital frequency ( Nf _orb ), and 74 combination frequencies. Ten Nf _orb peaks with S/N > 10 have very high amplitudes and are likely due to tidally excited oscillations (TEOs). The remaining Nf _orb peaks (4 ≤ S/N ≤ 10) may be originated from the imperfect removal, or they are actually real TEOs. Four anharmonic frequencies can pair up and sum to give exact harmonics of the orbital frequency, suggesting the existence of nonlinear tidal processes in the eccentric binary system FX UMa. Eight independent frequencies in the range of 20–32 day ^−1 are typical low-order pressure modes of δ Scuti pulsators.

Keywords

• Eclipsing binary stars
• Pulsating variable stars