Tidal perturbations and eclipse mapping in the pulsations in the hierarchical triple system U~Gru
Cole Johnston, Andrew Tkachenko, Timothy Van Reeth, Dominic M. Bowman,, Kresimir Pavlovski, Hugues Sana, and Sanjay Sekaran

TL;DR
This study investigates the pulsations of the hierarchical triple system U Gru, demonstrating tidal influence on at least one mode and proposing eclipse mapping as a mechanism for observed frequency patterns.
Contribution
The paper provides the first detailed analysis of tidal effects on pulsations in U Gru, identifying a tidally perturbed mode and introducing eclipse mapping as an explanation for frequency spacings.
Findings
U Gru is likely a hierarchical triple system.
A single pulsation mode shows amplitude and phase variations due to tides.
Eclipse mapping can reproduce frequency series separated by the orbital frequency.
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…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Atmospheric Ozone and Climate · Astro and Planetary Science
