Correlated chaotic pressure modes in rapidly rotating stars (Vol. 50, No. 3)

Correlated chaotic pressure modes in rapidly rotating stars
Meridional section of a chaotic mode. The pressure P is represented, scaled by the distance to the rotation axis and the equilibrium density.

Correlated chaotic pressure modes in rapidly rotating starsPressure oscillations in stars can be monitored through the Fourier analysis of luminosity curves, observed e.g. in recent and future space missions. Similarly to seismologists on Earth, astronomers use the oscillation modes of stars to access properties of their interiors. This method has been very successful for slowly rotating stars. For rapidly rotating stars, since the star is flattened by centrifugal acceleration, the acoustic ray dynamics is more complex, with both regular and chaotic zones in phase space. The authors study the properties of chaotic modes in the domain of high frequencies. The numerical simulations show that chaotic modes produce specific regularities in the oscillation spectra. This is at odds with the expected properties of chaotic modes, usually distributed like the eigenvalues of random matrices. Through a semiclassical theory, they link this peculiarity to the strong decrease of the sound speed near the star surface. Chaotic modes could contribute to the regularities observed in Scuti stars, attributed so far to regular modes. (Vol. 50, No. 3)

B. Evano, B. Georgeo and F. Lignières, Correlations in the chaotic spectrum of pressure modes in rapidly rotating stars, EPL 125, 49002 (2019)