Saio, Hideyuki and Kurtz, Donald W. and Murphy, Simon J. and Antoci, Victoria L. and Lee, Umin (2017) Theory and evidence of global Rossby waves in upper main-sequence stars: r-mode oscillations in many Kepler stars. Monthly Notices of the Royal Astronomical Society, 474 (2). pp. 2774-2786. ISSN 0035-8711
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Abstract
Asteroseismic inference from pressure modes (p modes) and buoyancy, or gravity, modes (g modes) is ubiquitous for stars across the Hertzsprung–Russell diagram. Until now, however, discussion of r modes (global Rossby waves) has been rare. Here we derive the expected frequency ranges of r modes in the observational frame by considering the visibility of these modes. We find that the frequencies of r modes of azimuthal order m appear as groups at slightly lower frequency than m times the rotation frequency. Comparing the visibility curves for r modes with Fourier amplitude spectra of Kepler light curves of upper main-sequence B, A, and F stars, we find that r modes are present in many γ Dor stars (as first discovered by Van Reeth et al.), spotted stars, and so-called heartbeat stars, which are highly eccentric binary stars. We also find a signature of r modes in a frequently bursting Be star observed by Kepler. In the amplitude spectra of moderately to rapidly rotating γ Dor stars, r-mode frequency groups appear at lower frequency than prograde g-mode frequency groups, while in the amplitude spectra of spotted early A to B stars, groups of symmetric (with respect to the equator) r-mode frequencies appear just below the frequency of a structured peak that we suggest represents an approximate stellar rotation rate. In many heartbeat stars, a group of frequencies can be fitted with symmetric m = 1 r modes, which can be used to obtain rotation frequencies of these stars.
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| Item Type: | Article (Commonwealth Reporting Category C) |
|---|---|
| Refereed: | Yes |
| Item Status: | Live Archive |
| Additional Information: | File reproduced in accordance with the copyright policy of the publisher/author. |
| Faculty/School / Institute/Centre: | No Faculty |
| Faculty/School / Institute/Centre: | No Faculty |
| Date Deposited: | 02 May 2022 23:13 |
| Last Modified: | 16 May 2022 03:11 |
| Uncontrolled Keywords: | Binaries: eclipsing; Stars: early-type; Stars: oscillations; Stars: rotation; Stars: variables: general; Starspots; 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/10.1093/mnras/stx2962 |
| URI: | http://eprints.usq.edu.au/id/eprint/47950 |
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