Doppler imaging of stellar non-radial pulsations

I. Techniques and numerical experiments

Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria e-mail: oleg@astro.univie.ac.at

Received: 31 March 2004
Accepted: 29 April 2004

Abstract

We present a novel technique aimed at the investigation of the geometry of surface velocity fluctuations in non-radially pulsating stars. Our method is based on the Doppler imaging principle and enables an accurate reconstruction of a two-dimensional map of the pulsational disturbances using spectroscopic time-series observations. No specific assumptions on the shape of the pulsation geometry are made. This opens a unique possibility to go beyond the traditional mode identification analyses and study complex rotationally and magnetically distorted non-radial pulsation modes which cannot be described by a single spherical harmonic function. Performance and intrinsic limitations of the new Doppler imaging procedure are assessed with inversions of simulated data. Based on the results of these numerical tests we conclude that a reliable recovery of the surface pulsation velocity structures can be achieved for all types of pulsation geometries accompanied by significant line profile variations. It is also demonstrated that the Doppler mapping of the pulsation velocity field is remarkably robust with respect to errors in the adopted stellar parameters.