Interior rotation modelling of the $\beta$ Cep pulsator HD 192575 including multiplet asymmetries

TL;DR

This study constrains the internal rotation profile of the massive $eta$ Cep star HD 192575 using asteroseismic data, multiplet asymmetries, and improved modeling, revealing weak differential rotation and highlighting the importance of mode identification.

Contribution

First detailed rotation inversion for a $eta$ Cep pulsator, integrating multiplet asymmetries and asteroseismic modeling to probe internal stellar rotation.

Findings

Most rotation profiles indicate weak radial differential rotation.

Rotation ratio between core and envelope is below two.

Mode asymmetries are sensitive to mode identification and stellar structure.

Abstract

Rotation plays an important role in stellar evolution. However, the mechanisms behind the transport of angular momentum in stars at various stages of their evolution are not well understood. To improve our understanding of these processes, it is necessary to measure and validate the internal rotation profiles of stars across different stages of evolution and mass regimes. Our aim is to constrain the internal rotation profile of the 12Msun $\beta$ Cep pulsator HD 192575 from the observed pulsational multiplets and the asymmetries of their component frequencies. We update the forward asteroseismic modelling of HD 192575 based on new TESS observations. We invert for the rotation profile from the symmetric part of the splittings, and compute the multiplet asymmetries due to the Coriolis force and stellar deformation treated perturbatively. We compare the computed asymmetries with the observed asymmetries. Our new forward asteroseismic modelling is in agreement with previous results, but with increased uncertainties, partially due to increased frequency precision, requiring us to relax certain constraints. Ambiguity in the mode identification is the main source of the uncertainty, which also affects the inferred rotation profiles. Almost all acceptable rotation profiles occur in the regime below 0.4/d and favour weak radial differential rotation, with a ratio of core and envelope rotation below two. We find that the quality of the match between the observed and theoretically predicted mode asymmetries is strongly dependent on the mode identification and the internal structure of the star. Our results offer the first detailed rotation inversion for a $\beta$ Cep pulsator. They show that the rotation profile and the mode asymmetries provide a valuable tool to further constrain the evolutionary properties of HD 192575, and in particular the details of angular momentum transport in massive stars.