Tidally Perturbed Oblique Pulsations in the Hierarchical Triple System V1031 Orionis

Abstract: We present TESS photometry of the triple star system V1031 Ori (AB)C, which exhibits short-period oscillations superimposed on an eclipsing light curve. The high-quality data were analyzed in detail and combined with the published spectroscopic measurements to obtain the fundamental stellar parameters of the program target. The masses and radii of the eclipsing pair (AB) were determined to about 0.5 \% and 0.7 \% precision, respectively. We found 23 significant frequencies in two ranges of $&lt;$ 2 day$<sup>{-1}$ and 10.9$-$12.7 day$<sup>{-1}$ from the eclipse-subtracted residuals. Among them, sixteen in the gravity ($g$)-mode region may be aliases and artefacts due to imperfect removal of the systematic trends and the binary effects from the TESS data. Seven frequencies in the pressure ($p$)-mode region were separated by the orbital frequency and split by the average offset of 0.042 $\pm$ 0.003 day$<sup>{-1}$ from their adjacent harmonics. Further, the pulsation amplitudes are clearly modulated with the binary star orbit. The results indicate that the $p$-mode frequencies are tidally perturbed pulsations from the secondary component and the pulsation axis could be aligned with the tidal axis.