Cotton, D.V. ; Buzasi, D.L. ; Aerts, C. ; Bailey, J. ; Burssens, S. ; Pedersen, M.G. ; Stello, D. ; Kedziora-Chudczer, L. ; De Horta, A. ; De Cat, P. ; Lewis, F. ; Malla, S.P. ; Wright, D.J. ; Bott, K.

published in Nature Astronomy, 6, pp. 154--164

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, f_2, 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.

DOI: 10.1038/s41550-021-01531-9