Extended Data Fig. 1: Comparison of the radiative envelope of a MESA stellar evolution model to a polytropic approximation with Γ = 1.307. | Nature Astronomy

Extended Data Fig. 1: Comparison of the radiative envelope of a MESA stellar evolution model to a polytropic approximation with Γ = 1.307.

From: Breaking waves on the surface of the heartbeat star MACHO 80.7443.1718

Extended Data Fig. 1

The polytrope model joins to an isothermal atmosphere outside of the stellar profile. The MESA model has evolved just past the ignition of Helium in the core when it reaches the conditions matching those observed in MACHO 80.7443.1718. The right-hand panel compares the propagation diagram of the MESA and polytropic models, showing the dimensionless Lamb frequency (Sl, evaluated for l = 2) and Brunt-Väisälä frequency (N). Acoustic, p-modes propagate above the envelope set by these two frequencies, while buoyancy, g-modes propagate below.

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