7 Parallaxes

Previously we could only suggest that the stars appeared to be giants, based upon lines of evidence coming from colors, photometric indices and color-spectral type relations. With the HIPPARCOS data we can now provide absolute magnitudes with errors of the absolute magnitudes is equal or less than $\pm 0.3$. The corresponding values are quoted in Table 7, where the absolute magnitudes were corrected for binarity, if necessary. Figure 2 shows that on the average the stars lie $\rm 1^m35\pm 0.76$ above the main sequence. This is equivalent to a radius larger by a factor of $4.7\pm 3$ implying that the average radius of a shell star is about 4.7 times as large as the normal radius of a dwarf star. The shell is thus located rather close to the star. In Be stars we found from a different procedure $3.2\pm 1.4$ (Jaschek & Jaschek 1992). Since within the errors the two values coincide, this underlines the close similarity of both kinds of objects.

  

Figure 2: The R ratio as a function of spectral type and luminosity class for standards MK stars

  

Table 7: Absolute magnitudes of the stars of our sample

M(corr) are corrected for binarity.