Observed normalised interstellar Na i D absorption-line profiles (dots). The solid line shows the adopted fitted profile obtained with the parameters given in Table 4. The locations of the identified components are indicated by the tick marks. Telluric lines have been removed from the normalised profiles by applying a synthetic telluric spectrum (see text). The new Hipparcos stellar distance (van Leeuwen 2007) is given in the right-hand bottom of each panel.