Tidal perturbations and eclipse mapping in the pulsations in the hierarchical triple system U~Gru

Abstract

Context. Unambiguous examples of the influence of tides on self-excited, free stellar pulsations have recently been observationally detected in space-based photometric data. Aims. We aim to investigate U Gru and contextualise it within the growing class of tidally influenced pulsators. Initial analysis of U Gru revealed frequencies spaced by the orbital frequency that are difficult to explain by currently proposed tidal mechanisms. Methods. We re-investigate the TESS photometry of U Gru alongside new uves spectroscopy. We analyse the uves spectroscopy with least-squares deconvolution and spectral disentangling techniques, and perform an atmospheric analysis. We remove the binary signature from the light curve using an effective model in order to investigate the pulsation signal in the residuals. We track the amplitudes and phases of the residual pulsations as a function of the orbital period to reveal their tidal influence. Results. We establish that U Gru is likely a hierarchical triple system. We identify a single p mode oscillation to exhibit amplitude and phase variation over the binary orbit. We propose a toy model to demonstrate that the series of frequencies separated by the orbital frequency can be reproduced by eclipse mapping. We find no evidence of modulation to the other independent oscillation modes. Conclusions. We demonstrate that U Gru hosts at least one tidally perturbed pulsation. Additionally we argue that eclipse mapping of the dominant, tidally perturbed mode can produce the series of frequencies separated by the observed orbital frequency. Our simulations show that the effects of eclipse mapping are mode dependent, and are not expected to produce an observable signature for all pulsation modes in an eclipse binary.

Accepted for publication in Astronomy & Astrophysics. 13 pages, 10 figures, 3 tables, 1 appendix

References in corpus (17)

• Array Programming with NumPy
• The Transiting Exoplanet Survey Satellite
• exoplanet: Gradient-based probabilistic inference for exoplanet data & other astronomical time series
• Finding binaries among Kepler pulsating stars from phase modulation of their pulsations
• The Gaia-ESO Survey: processing of the FLAMES-UVES spectra
• The single-sided pulsator CO~Camelopardalis
• Discovery of $\beta$ Cep pulsations in the eclipsing binary V453 Cygni
• Tidally Trapped Pulsations in Binary Stars
• A beta Cephei pulsator and a changing orbital inclination in the high-mass eclipsing binary system VV Orionis
• Tidally perturbed pulsations in the pre-main sequence $\delta$ Scuti binary RS Cha
• HD 24355 observed by the Kepler K2 mission: A rapidly oscillating Ap star pulsating in a distorted quadrupole mode
• Mass transfer and tidally tilted pulsation in the Algol-type system TZ Dra
• Characterization of the variability in the O+B eclipsing binary HD 165246
• Tidally Tilted Pulsations in HD 265435, a subdwarf B Star with a Close White Dwarf Companion
• Tidally Perturbed Oblique Pulsations in the Hierarchical Triple System V1031 Orionis
• BRITE-Constellation photometry of $\bpi^5$ Orionis, an ellipsoidal SPB variable
• V456 Cyg: An eclipsing binary with tidally perturbed g-mode pulsations

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