Kinematic structure of the atmosphere and envelope of the post-AGB star HD56126

Abstract

We present results of an analysis of the optical spectrum of the post-AGB star HD56126 (IRAS 07134+1005) based on observations made with the echelle spectrographs of the 6-m telescope with spectral resolutions of R=25000 and 60000 at 4012-8790 AA. The profiles of strongest lines (HI; FeII, YII, BaII absorptions, etc.) formed in the expanding atmosphere at the base of the stellar wind have complex and variable shapes. To study the kinematics of the atmosphere, the velocities of individual features in these profiles must be measured. Differential line shifts of up to Vr=15-30 km/s have been detected from the lines of metals and molecular features. The star's atmosphere simultaneously contains both expanding layers and layers falling onto the star. A comparison of the data for different times demonstrates that both the radial velocity and the velocity pattern in whole are variable. The position of the molecular spectrum is stable, implying stability of the expansion velocity of the circumstellar envelope around HD56126 detected in observations in the C_2 and NaI lines.