Properties of the ionisation glitch

Context. Determining the properties of solar-like oscillating stars can be subject to many biases. A particularly important example is helium-mass degeneracy, where uncertainties regarding internal physics cause a poor determination both mass and surface helium content. Accordingly, an independent estimate needed overcome this degeneracy. promising way obtain such exploit so-called ionisation glitch, that is, deviation from asymptotic oscillation frequency pattern caused by rapid structural variation in He zones. Aims. Although it progressively becoming more sophisticated, glitch-based approach faces problems inherent its current modelling as need for calibration using realistic stellar models. This requires physical model region explicitly involves parameters interest, abundance, Y s . Methods. Through thermodynamic treatment region, analytical approximation first adiabatic exponent Γ 1 presented. Results. The induced structure found depend on only three parameters, including abundance electron degeneracy ψ CZ convective region. thus defined allows wide variety structures described, particular able approximate work we conducted enables us study perturbations causing glitch. More elaborate forms than those are usually assumed found. It also suggested there might stronger dependence convection zone position rather amount itself. Conclusions. When analysing glitch signature, emphasise importance having relation take these additional dependences into account.