2 The program stars

The stars selected belong to OB associations or clusters, so that we have a good estimate of the distance and therefore of the absolute magnitude. We have used the catalogue of Garmany & Stencel (1992) which is largely based on the cluster distances obtained by Humphreys (1978). In these catalogues the sample is biased towards early A-type supergiants. We have tried hard to get a good sample of all the luminosity classes for each spectral type since we expect significant luminosity effects in the lines formed in the wind. The whole sample is listed in Table 1; ordered by right ascension and identified by their entry number in the HD or BD catalogues. Another usual identification (as the SAO number or the variable star name) is provided in the second column. The equatorial coordinates ($\alpha$(2000.0), $\delta$(2000.0)) are given in the third and fourth column. The apparent visual magnitudes are listed in the fifth column. The absolute visual magnitude and the OB associations to which each of the stars belongs are given in the sixth and seventh columns respectively. The absolute magnitudes come from the catalogues cited above and they are calculated from the adopted distance to the association.

Most of the stars have been observed both in the ultraviolet and visible, although the less luminous stars could not be observed with the IUE satellite and only two southern stars were observed in the visible. We summarize this information in the last two columns of Table 1.

In Table 2 we give the tabulated spectral types of each star taken from the literature (Humphreys 1978; Garmany & Stencel 1992; Bouw 1981; Fernie 1983; Stothers 1991; Kaltcheva & Georgiev 1994; Cananzi et al. 1993).

  

Table 1: Basic properties of the program stars

  

Table 2: Spectral types