4 Radial velocities

There are very few absorption lines and most of these are affected by emission and or a shell component, therefore we derived the average radial velocity from the well defined emission lines. The average radial velocity from the emission lines is found to be 50 $\pm$ 2 km s^-1. Morrison & Zimba (1989) using 14 best absorption lines found the radial velocity to be $69 \pm 1$ km s^-1. From the equivalent widths of FeI absorption lines given by Rosenzweig et al. (1997) we find no correlation between log $gf - \chi\Theta$ and heliocentric radial velocity (Fig. 8). However, Bakker et al. (1996a) found a correlations between log $gf - \chi\Theta$ and heliocentric radial velocities of HD 101584 in the UV. The discripancy could be due to the poor resolution of Rosenzweig et al. (1997) data compared to that of Bakker et al. (1996a). The large scatter seen in the radial velocities could be due to pulsation. Similar velocity variations were noticed in other post-AGB supergiants (García-Lario et al. 1997; Hrivnak 1997).

  

Figure 8: The plot in the upper panel does not show any correlation between the optical depth and the helio centric radial velocity for the FeI absorption lines of HD 101584 in the wavelength region 3600 Å - 4500 Å. The plot in the lower panel shows the normalized strength of FeI absorption lines in the wavelength region 3600 Å to 4500 Å versus the optical depth. It shows clearly that the lines are forming at different optical depths. The equivalent widths are taken from the paper by Rosenzweig et al. (1997)