Doppler Imaging of Stellar Non-Radial Pulsations

Test of the capabilities of Doppler imaging technique for reconstruction of the non-radial pulsation velocity field. The rectangular and spherical plots show amplitude distribution for the vertical component of the pulsation velocity field due to the l=6, m=4 mode recovered from the simulated data. No a priori assumptions about functional form of the pulsational disturbances has been introduced. A complete description of time-dependent pulsational fluctuations requires imaging of two velocity amplitude maps (or, equivalently, reconstruction of the surface variation of the pulsation amplitude and phase) for each vector component of the velocity field. These two velocity amplitude maps are presented in the left and right groups of panels.
Kochukhov, 2004, A&A, 423, 613
The first Doppler image of the stellar pulsation velocity field delivers a solution of the long-standing problem of the pulsation geometry of magnetic peculiar stars. These maps show the vertical velocity component of non-radial pulsations in the roAp star HR 3831. Only one amplitude map contains significant structures which is a signature of a nearly axisymmetric pulsation. Pulsation axis is inclined by about 90o relative to the stellar axis of rotation and is demonstrated to be aligned with the axis of the stellar magnetic field. Pulsations are due to the dipole l=1 mode, distorted by the magnetic field in a way that significant axisymmetric l=3 component appears and pulsation amplitude is increased at the magnetic poles.
Kochukhov, 2004, ApJ, 615, L149