LINE-PROFILE VARIATIONS CAUSED BY LOW-FREQUENCY NONRADIAL PULSATIONS OF RAPIDLY ROTATING STARS

We present line profile variations caused by low-frequency (in the frame fixed to the star) nonradial g-mode oscillations of a rotating star. For a nonradial oscillation mode whose oscillation frequency in the co-rotating frame is comparable to or smaller than the rotation frequency, the latitudinal dependence of the oscillation amplitude deviates significantly from that for a nonrotating star. Rotation usually causes oscillations confined to a narrow equatorial belt as well as causing toroidal velocity fields. Such effects are included in our calculations of line profile variations by expressing the angular dependence of the amplitude as a linear combination of terms proportional to spherical harmonics Ylm(θ φ) (l ≥ |m|). The concentration of the amplitude of the oscillations toward the equator leads to a reduction in the strength of the bumps in line profiles if the maximum velocity of nonradial pulsation is fixed. For the same normalization, the line profile variations due to the sectoral prograde (in the co-rotating frame) mode are most visible, while those caused by retrograde waves are almost invisible due to a cancellation effect. The toroidal component generated by stellar rotation appreciably affects the line profile variation of some modes. We also discuss the effect of the surface temperature variation on the line profiles.