Buoyancy glitches in pulsating stars revisited
Astronomy & Astrophysics(2024)
摘要
Sharp structural variations induce specific signatures on stellar pulsations
that can be studied to infer localised information on the stratification of the
star. This information is key to improve our understanding of the physical
processes that lead to the structural variations and how to model them. Here we
revisit and extend the analysis of the signature of different types of buoyancy
glitches in gravity-mode and mixed-mode pulsators presented in earlier works,
including glitches with step-like, Gaussian-like, and Dirac-δ-like
shapes. In particular, we provide analytical expressions for the perturbations
to the periods and show that these can be reliably used in place of the
expressions provided for the period spacings, with the advantage that the use
of the new expressions does not require modes with consecutive radial orders to
be observed. Based on a comparison with two limit cases and on simulated data,
we further tested the accuracy of the expression for the Gaussian-like glitch
signature whose derivation in an earlier work involved a significant
approximation. We find that the least reliable glitch parameter inferred from
fitting that expression is the amplitude, which can be up to a factor of two
larger than the true amplitude, reaching this limit when the glitch is small.
We further discuss the impact on the glitch signature of considering a glitch
in the inner and outer half of the g-mode cavity, emphasising the break of
symmetry that takes place in the case of mixed-mode pulsators.
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