scieee AI-readable full text Open interactive document viewer

Visibilities of damped mixed modes

Müller, Jonas; Coppée, Quentin; Hekker, Saskia

Abstract

The visibility of oscillation modes is a measure of their mean energy. We have developed a formalism for estimating the asymptotic visibility of multipolar mixed modes that accounts for both convective damping at the surface and dissipation of mode energy by a strong core magnetic field. In this work, we use these asymptotic visibilities to generate synthetic power density spectra from numerical stellar models and compare them with observations. In particular, we study to what extent the equipartition of energy between modes of different spherical degrees is realized in observed power spectra. Furthermore, we vary the magnetic field strength to investigate the occurrence of red giant stars with suppressed dipole modes and the morphology of their power spectra as they ascend the red giant branch.

Full text

1. Heidelberger Institut für Theoretische Studien, Heidelberg, Germany 2. Zentrum für Astronomie (ZAH/LSW), Heidelberg, Germany [email protected]g Jonas Müller1, 2, Quentin Coppée1, 2, Francisca Espinoza-Rojas1, 2, Saskia Hekker1, 2 (variables) ●We have developed a formalism to calculate asymptotic properties of damped mixed modes (based on Takata 2016b). ●This can be used to generate synthetic power spectra of stellar models. Visibilities of damped mixed modes Visibilities are amplitude ratios weighted by a geometrical factor that depends on the observation methods and the spherical degree : Damping processes operating in the stellar core decrease the multipole mode visibility. ●In observations, visibilities are estimated by integrating segments of the PSD (see shaded regions above). ➢This can lead to observational biases. ●We apply the observational methods to our synthetic PSDs to allow a meaningful comparison of theoretical and observed visibilities. D “Normal” mixed modes Depressed mixed modes Depressed mixed modes Fully suppressed modes Not mixed Core damping can explain the range of observed dipole mode visibilities. The geometrical factor is , in agreement with predictions from Ballot et al. (2011). No core damping Stronger core damping CBA A B C D Dipole mode visibility Observed visibilities are susceptible to stochastic scattering. Theoretical estimates for a 1.5 model. Different masses yield slightly different results. Observed visibilities from Stello et al. (2016a,b). Theoretical predictions have to be compared to averages. Shaded regions correspond to different radial mode linewidths. Magnetic damping in the stellar core according to Müller et al. (2025). Initial main-sequence field strengths range from 1 kG to 100 kG (see colors below).