LUMINOSITY ATTENUATION AND DISTANCES OF RED GIANT STARS

The M(V) Of M red variable stars is increased by the molecular TiO ban ds which grow from MO to M10 in an inherent spectral darkening sequenc e. The M(V) is the result of both the effective visual nux and the equ ivalent radius. The equivalent radius is apparently smaller than the e mpirical radius due to a molecular covering process in stars later tha n M3. The full range of optical red giant stars forms a sequence from the brightest M-early spectral types(S Car, MO(max), M(V) corresponds to -3.2 mag) to the faintest M-latest spectral types (IK Tau, M10.5(mi n), M(V) corresponds to 16.5 mag). The typical Miras and SR stars of M -medium and M-late spectral types are between these two extremes. The sequence has a range of 20 mag on the visual HR diagram which extends from the red giant branch (RGB) passing beyond the MV of red dwarf sta rs as far as the point where it intercepts with the prolongation of ZA MS in the latest spectral type. Typical MIG-stars at 200 pc has a V co rresponds to 20 mag. M-latest stars at larger distances are unobservab le stars in the visual band. The distances of 134 variable stars are a lso given. The distances to 86 stars were determined by using a pure p hotometric method, while preliminary distances (less than 200 pc) for the remaining 48 M-latest stars were determined by the spectral-photom etric method. Since the local stellar density of M stars up to 100 pc rises at least 7.5 times, it is possible to discuss that the long-stan ding problem of dark matter in spiral galaxies could be resolved by th ese very dim massive giant stars and by the molecular covered stars at the extreme end of the attenuating sequence. Furthermore, post M-late st stars may be the only nonvisual stellar objects that can explain th e enormous quantity of faint and point infrared sources found by IRAS. These weak objects suggest the existence of an infrared Milky Way whi ch is more dense than the optical one.