With the increasing precision of asteroseismic observations, it becomes possible to reliably measure oscillation properties of an increasing number of stars. Interpreting these measurements requires a good theoretical understanding of their link to fundamental stellar properties. We focus on the phase offset in gravity-mode (g-mode) frequencies, which is imprinted on the asymptotic eigenfrequency pattern of mixed dipole modes observed in stars on the red-giant branch. We aim to unravel its physical origin and thus enable an informed interpretation of observations. Using stellar models, we empirically tested the contribution of the g-mode offset ɛ_ (which is related to the wave reflection at cavity boundaries and is commonly considered to be the dominant phase term) and glitches to the total observable phase. We found that in addition to ɛ_ buoyancy glitches play an important role in the correct interpretation of the g-mode frequency phase. We further found that glitches in the evanescent zone also contribute to the phase, and we present a formalism to quantify this contribution. Finally, we propose a modification to the widely used formula for ɛ_ The g-mode frequency phase carries more information than previously considered. It has large analytic potential for studying not only the reflection properties of the buoyancy cavity, but also the properties of glitches in the Brunt-Väisälä frequency.
Lier et al. (Fri,) studied this question.