FX UMa: A New Heartbeat Binary System with Linear and Non-linear Tidal Oscillations and delta Sct Pulsations

TL;DR

This study analyzes FX UMa, an eclipsing binary with complex tidal oscillations and delta Scuti pulsations, revealing tidally excited oscillations, non-linear tidal effects, and stellar pulsation characteristics.

Contribution

It provides the first detailed analysis combining photometry and spectroscopy of FX UMa, identifying tidally excited oscillations and non-linear tidal interactions in this binary system.

Findings

Identification of 103 frequencies including 12 independent and 17 orbital harmonics.

Detection of high-amplitude tidally excited oscillations (TEOs).

Evidence of non-linear tidal processes through harmonic frequency pairing.

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 (Nforb), and 74 combination frequencies. Ten Nforb peaks with S/N > 10 have very high amplitudes and are likely due to tidally excited oscillations (TEOs). The remaining Nforb 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 non-linear tidal processes in the eccentric binary system FX UMa. Eight independent frequencies in the range of 20 to 32 day$^{-1}$ are typical low-order pressure modes of delta Scuti pulsators.