We have investigated the F0V star V398 Aurigae ( = 9 Aur ) under the assumption that it is undergoing non-radial gravity mode oscillations and that the two principal periods given by Krisciunas et al .
( 1995 ) are correct .
We find that the two periods are manifestations of an \ell = 3 ,|m| = 1 spheroidal mode and its toroidal corrections due to the rotation of the star .
As far as we know , this is the first detection of toroidal correction terms in a real star .
The two modes probably are the result of rotational splitting .

Our analysis provides for the first time a physical explanation of certain characteristics of the observed behavior of the star .
The amplitude of the radial part of the pulsation for f _ { 1 } = 0.795 d ^ { -1 } is a factor of 4 larger than the one for f _ { 2 } = 0.346 d ^ { -1 } .
Since the photometric variability is determined mostly by temperature variations , which in turn are determined by the radial part of the pulsation , the photometric variability is dominated by the mode with frequency f _ { 1 } .
On the other hand , f _ { 2 } is the more pronounced one in all three spectroscopic moment variations ( including the radial velocity ) , reflecting that the transverse displacement of f _ { 2 } , and not the one of f _ { 1 } , dominates the velocity behavior .