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Tidally trapped pulsations in binary stars

Fuller, J. and Kurtz, D. W. and Handler, G. and Rappaport, S. (2020) Tidally trapped pulsations in binary stars. Monthly Notices of the Royal Astronomical Society, 498 (4). pp. 5730-5744. ISSN 0035-8711. doi:10.1093/mnras/staa2376.

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A new class of pulsating binary stars was recently discovered, whose pulsation amplitudes are strongly modulated with orbital phase. Stars in close binaries are tidally distorted, so we examine how a star’s tidally induced asphericity affects its oscillation mode frequencies and eigenfunctions. We explain the pulsation amplitude modulation via tidal mode coupling such that the pulsations are effectively confined to certain regions of the star, e.g. the tidal pole or the tidal equator. In addition to a rigorous mathematical formalism to compute this coupling, we provide a more intuitive semi-analytic description of the process. We discuss three resulting effects: (1) Tidal alignment, i.e. the alignment of oscillation modes about the tidal axis rather than the rotation axis; (2) Tidal trapping, e.g. the confinement of oscillations near the tidal poles or the tidal equator; (3) Tidal amplification, i.e. increased flux perturbations near the tidal poles where acoustic modes can propagate closer to the surface of the star. Together, these phenomena can account for the pulsation amplitude and phase modulation of the recently discovered class of ‘tidally tilted pulsators.’ We compare our theory to the three tidally tilted pulsators HD 74423, CO Cam, and TIC 63328020, finding that tidally trapped modes that are axisymmetric about the tidal axis can largely explain the first two, while a non-axisymmetric tidally aligned mode is present in the latter. Finally, we discuss implications and limitations of the theory, and we make predictions for the many new tidally tilted pulsators likely to be discovered in the near future.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemMovies of tidally tilted pulsators
Fuller, J.0000-0002-4544-0750
Kurtz, D. W.0000-0002-1015-3268
Handler, G.0000-0001-7756-1568
Rappaport, S.0000-0003-3182-5569
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Received: 04 June 2020; Revision received: 31 July 2020; Accepted: 03 August 2020; Published: 22 September 2020. We thank the anonymous referee for a thorough review of this manuscript. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958. JF is thankful for support through an Innovator Grant from The Rose Hills Foundation, and the Sloan Foundation through grant FG-2018-10515. GH gratefully acknowledges funding through National Science Centre of Poland (NCN) grant 2015/18/A/ST9/00578. Data Availability: Data and source code is available upon request to the authors.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Rose Hills FoundationUNSPECIFIED
Alfred P. Sloan FoundationFG-2018-10515
National Science Centre (Poland)2015/18/A/ST9/00578
Subject Keywords:binaries: close – stars: individual: HD 74423 – stars: individual: CO Cam – stars: individual: TIC 63328020 – stars: oscillations – stars: variables: Scuti
Issue or Number:4
Record Number:CaltechAUTHORS:20200916-112956523
Persistent URL:
Official Citation:J Fuller, D W Kurtz, G Handler, S Rappaport, Tidally trapped pulsations in binary stars, Monthly Notices of the Royal Astronomical Society, Volume 498, Issue 4, November 2020, Pages 5730–5744,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105430
Deposited By: George Porter
Deposited On:16 Sep 2020 20:22
Last Modified:16 Nov 2021 18:43

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