Polarimetric detection of non-radial oscillation modes in the β Cephei star β Crucis
Abstract
Here we report the detection of polarization variations due to non-radial modes in the β Cephei star β Crucis. In so doing we confirm 40-year-old predictions of pulsation-induced polarization variability and its utility in asteroseismology for mode identification. In an approach suited to other β Cephei stars, we combine polarimetry with space-based photometry and archival spectroscopy to identify the dominant non-radial mode in polarimetry, f2, as mode degree ℓ = 3, azimuthal order m = −3 (in the m-convention of Dziembowski) and determine the stellar axis position angle as 25 (or 205) ± 8°. The rotation axis inclination to the line of sight was derived as ~46° from combined polarimetry and spectroscopy, facilitating identification of additional modes and allowing for asteroseismic modelling. This reveals a star of 14.5 ± 0.5 M⊙ and a convective core containing ~28% of its mass—making β Crucis the most massive star with an asteroseismic age.
- Publication:
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Nature Astronomy
- Pub Date:
- January 2022
- DOI:
- 10.1038/s41550-021-01531-9
- arXiv:
- arXiv:2205.11679
- Bibcode:
- 2022NatAs...6..154C
- Keywords:
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- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 33 pages, 11 figures, 8 tables (incl. Supplementary Information). Accepted version