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

Scientific paper - Original scientific paper

• Author: C. Johnston
• Author: A. Tkachenko
• Author: T. Van Reeth
• Author: D. M. Bowman
• Author: K. Pavlovski
• Author: H. Sana
• Author: S. Sekaran
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

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. An initial analysis of U Gru revealed frequencies spaced by the orbital frequency that are difficult to explain by currently proposed tidal mechanisms. Methods. We reinvestigate the TESS photometry for 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 that exhibits 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 eclipsing binary.

• Keywords (english): asteroseismology – binaries; eclipsing – stars; individual; U Gru – stars; oscillations – binaries; close
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Astronomy & Astrophysics
• Numbering: vol. 670, A167
• p-ISSN: 0004-6361
• e-ISSN: 1432-0746
• DOI: https://doi.org/10.1051/0004-6361/202244808
• URN:NBN: urn:nbn:hr:217:203031
• Publication: 2023-02-21
• Document URL: https://www.aanda.org/10.1051/0004-6361/202244808
• Type of resource: Text
• Access conditions: Open access
• Public note: Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication. Received 23 August 2022; Accepted 10 October 2022; Published online 21 February 2023.
• Created on: 2023-08-21 12:30:26