# Near-Core Acoustic Glitches are Not Oscillatory: Consequences for Asteroseismic Probes of Convective Boundary Mixing

**Authors:** Christopher J. Lindsay, J. M. Joel Ong, Sarbani Basu  
**arXiv:** [2304.06770](https://arxiv.org/abs/2304.06770)  
**Date:** 2023-04-13  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.06770v1/

## Key points

- Asteroseismology is a powerful tool for studying the internal structure and physical processes of main sequence stars.
- Pressure modes (p-modes) have been used to probe the structure of near-core layers of main sequence stars with convective cores.
- Limitations exist in using p-modes to study near-core mixing processes for intermediate-mass stars on the main sequence due to a sudden loss of sensitivity during the discontinuous transition between two phases in the evolution of inner turning points of p modes as determined by the JWKB approximation.
- Non-JWKB asymptotic analysis has been employed to derive a contrasting set of expressions for the effects that these structural properties will have on mode frequencies, resulting in non-oscillatory, degree-dependent perturbations to star's oscillation mode frequencies which contrasts with outer glitches.
- Near-core acoustic glitches exhibit strong angular degree dependence even at low degrees, which has important implications for using p-modes to study near-core mixing processes for intermediate-mass stars on the main sequence and interpreting near-center acoustic glitches in other astrophysical configurations such as red giants.
- Scaled p-mode radial Lagrangian displacement wavefunctions may be approximated by linear combinations of Riccati–Bessel functions with argument ωt, described well by using only Bessel function of first kind with further position dependent phases added to argument.
- This research provides new insights into how asteroseismology can be used effectively to study interior structures and physical processes in main sequence stars with convective cores and highlights potential limitations and solutions when analyzing data from p–modes.

## Summary

Asteroseismology has been a powerful tool for studying the internal structure and physical processes of main sequence stars. In particular, pressure modes (p-modes) near the frequency of maximum oscillation power have been used to probe the structure of the near-core layers of main sequence stars with convective cores. However, there are limitations in using p-modes to study near-core mixing processes for intermediate-mass stars on the main sequence due to a sudden loss of sensitivity during the discontinuous transition between two phases in the evolution of inner turning points of p modes as determined by the JWKB approximation. To overcome this limitation, non-JWKB asymptotic analysis has been employed to derive a contrasting set of expressions for the effects that these structural properties will have on mode frequencies. The analysis shows that a sufficiently near-core perturbation to stellar structure results in non-oscillatory, degree-dependent perturbations to star's oscillation mode frequencies which contrasts with outer glitches. Numerical simulations also demonstrate that these near-core acoustic glitches exhibit strong angular degree dependence even at low degrees. These findings have important implications for using p-modes to study near-core mixing processes for intermediate-mass stars on the main sequence and for interpreting near-center acoustic glitches in other astrophysical configurations such as red giants. Additionally, from local asymptotic theory it is known that scaled p-mode radial Lagrangian displacement wavefunctions may be approximated by linear combinations of Riccati–Bessel functions with argument ωt. These linear combinations are well described by using only Bessel function of first kind with further position dependent phases added to argument. Overall, this research provides new insights into how asteroseismology can be used effectively to study interior structures and physical processes in main sequence stars with convective cores and highlights potential limitations and solutions when analyzing data from p–modes.