Tidally trapped pulsations in a close binary star system discovered by TESS

Handler, G. and Kurtz, D. W. and Rappaport, S. A. and Saio, H. and Fuller, J. and Jones, D. and Guo, Z. and Chowdhury, S. and Sowicka, P. and Alicavus, F. Kahraman and Streamer, M. and Murphy, S. J. and Gagliano, R. and Jacobs, T. L. and Vanderburg, A. (2020) Tidally trapped pulsations in a close binary star system discovered by TESS. Nature Astronomy, 4 (7). pp. 684-689.


It has long been suspected that tidal forces in close binary stars could modify the orientation of the pulsation axis of the constituent stars. Such stars have been searched for, but until now never detected. Here we report the discovery of tidally trapped pulsations in the ellipsoidal variable HD 74423 in Transiting Exoplanet Survey Satellite (TESS) space photometry data. The system contains a δ Scuti pulsator in a 1.6 d orbit, whose pulsation mode amplitude is strongly modulated at the orbital frequency, which can be explained if the pulsations have a much larger amplitude in one hemisphere of the star. We interpret this as an obliquely pulsating distorted dipole oscillation with a pulsation axis aligned with the tidal axis. This is the first time that oblique pulsation along a tidal axis has been recognized. It is unclear whether the pulsations are trapped in the hemisphere directed towards the companion or in the side facing away from it, but future spectral measurements can provide the solution. In the meantime, the single-sided pulsator HD 74423 stands out as the prototype of a new class of obliquely pulsating stars in which the interactions of stellar pulsations and tidal distortion can be studied.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 15 Jul 2022 00:06
Last Modified: 03 Aug 2022 04:10
Uncontrolled Keywords: Astrophysics - Solar and Stellar Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.1038/s41550-020-1035-1
URI: http://eprints.usq.edu.au/id/eprint/47882

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