Figure 4.

Apparent intersection (due to avoided crossing) of the axisymmetric first quasi-radial overtone (H₁) and the first overtone of the l=4 p-mode (in the Cowling approximation). Frequencies are normalized by , where ρ_c is the central energy density of the star. The rotational frequency f_rot at the mass-shedding limit is 0.597 (in the above units). Along continuous sequences of computed frequencies, mode eigenfunctions are exchanged at the avoided crossing. Defining quasi-normal mode sequences by the shape of their eigenfunction, the H₁ sequence (filled boxes) appears to intersect with the ⁴p₁ sequence (triangle), but each sequence shows a discontinuity, when the region of apparent intersection is well resolved. (Figure 3 of Yoshida and Eriguchi [330]; used with permission.)