Tidally Distorted Stars Are Triaxial Pulsators
Stars in close binaries are tidally distorted, and this has a strong effect on their pulsation modes. We compute the mode frequencies and geometries of tidally distorted stars using perturbation theory, accounting for the effects of the Coriolis force and the coupling between different azimuthal ord...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad9eb2 |
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| author | Jim Fuller Saul Rappaport Rahul Jayaraman Don Kurtz Gerald Handler |
| author_facet | Jim Fuller Saul Rappaport Rahul Jayaraman Don Kurtz Gerald Handler |
| author_sort | Jim Fuller |
| collection | DOAJ |
| description | Stars in close binaries are tidally distorted, and this has a strong effect on their pulsation modes. We compute the mode frequencies and geometries of tidally distorted stars using perturbation theory, accounting for the effects of the Coriolis force and the coupling between different azimuthal orders m of a multiplet induced by the tidal distortion. For tidally coupled dipole pressure modes, the tidal coupling dominates over the Coriolis force and the resulting pulsations are “triaxial,” with each of the three modes in a multiplet “tidally tilted,” to be aligned with one of the three principal axes of the star. The observed amplitudes and phases of the dipole modes aligned orthogonal to the spin axis are modulated throughout the orbit, producing doublets in the power spectrum that are spaced by exactly twice the orbital frequency. Quadrupole modes have similar but slightly more complex behavior. This amplitude modulation allows for mode identification, which can potentially enable detailed asteroseismic analyses of tidally tilted pulsators. Pressure modes should exhibit this behavior in stellar binaries close enough to be tidally synchronized, while gravity modes should remain aligned with the star's spin axis. We discuss applications to various types of pulsating stars and the relationship between the tidal tilting of pulsations and the “single-sided” pulsations sometimes observed in very tidally distorted stars. |
| format | Article |
| id | doaj-art-af568f857c294cca87c53114fb42b802 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-af568f857c294cca87c53114fb42b8022025-01-21T10:00:47ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0197918010.3847/1538-4357/ad9eb2Tidally Distorted Stars Are Triaxial PulsatorsJim Fuller0https://orcid.org/0000-0002-4544-0750Saul Rappaport1https://orcid.org/0000-0003-3182-5569Rahul Jayaraman2https://orcid.org/0000-0002-7778-3117Don Kurtz3https://orcid.org/0000-0002-1015-3268Gerald Handler4https://orcid.org/0000-0001-7756-1568TAPIR, Mailcode 350-17, California Institute of Technology , Pasadena, CA 91125, USA ; jfuller@caltech.eduDepartment of Physics, Kavli Institute for Astrophysics and Space Research, MIT , Cambridge, MA 02139, USADepartment of Physics, Kavli Institute for Astrophysics and Space Research, MIT , Cambridge, MA 02139, USACentre for Space Research, North-West University , Dr Albert Luthuli Drive, Mahikeng 2735, South Africa; Jeremiah Horrocks Institute, University of Central Lancashire , Preston, PR1 2HE, UKNicolaus Copernicus Astronomical Center , Polish Academy of Sciences, ul. Bartycka 18, 00-716, Warsaw, PolandStars in close binaries are tidally distorted, and this has a strong effect on their pulsation modes. We compute the mode frequencies and geometries of tidally distorted stars using perturbation theory, accounting for the effects of the Coriolis force and the coupling between different azimuthal orders m of a multiplet induced by the tidal distortion. For tidally coupled dipole pressure modes, the tidal coupling dominates over the Coriolis force and the resulting pulsations are “triaxial,” with each of the three modes in a multiplet “tidally tilted,” to be aligned with one of the three principal axes of the star. The observed amplitudes and phases of the dipole modes aligned orthogonal to the spin axis are modulated throughout the orbit, producing doublets in the power spectrum that are spaced by exactly twice the orbital frequency. Quadrupole modes have similar but slightly more complex behavior. This amplitude modulation allows for mode identification, which can potentially enable detailed asteroseismic analyses of tidally tilted pulsators. Pressure modes should exhibit this behavior in stellar binaries close enough to be tidally synchronized, while gravity modes should remain aligned with the star's spin axis. We discuss applications to various types of pulsating stars and the relationship between the tidal tilting of pulsations and the “single-sided” pulsations sometimes observed in very tidally distorted stars.https://doi.org/10.3847/1538-4357/ad9eb2Binary starsStellar pulsationsAsteroseismologyTidal distortionDelta Scuti variable stars |
| spellingShingle | Jim Fuller Saul Rappaport Rahul Jayaraman Don Kurtz Gerald Handler Tidally Distorted Stars Are Triaxial Pulsators The Astrophysical Journal Binary stars Stellar pulsations Asteroseismology Tidal distortion Delta Scuti variable stars |
| title | Tidally Distorted Stars Are Triaxial Pulsators |
| title_full | Tidally Distorted Stars Are Triaxial Pulsators |
| title_fullStr | Tidally Distorted Stars Are Triaxial Pulsators |
| title_full_unstemmed | Tidally Distorted Stars Are Triaxial Pulsators |
| title_short | Tidally Distorted Stars Are Triaxial Pulsators |
| title_sort | tidally distorted stars are triaxial pulsators |
| topic | Binary stars Stellar pulsations Asteroseismology Tidal distortion Delta Scuti variable stars |
| url | https://doi.org/10.3847/1538-4357/ad9eb2 |
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