If a discontinuity is apparent in the above two-color distributions near
, the stars redder than this gap are considered normal red
giants (crosses) (Becker 1962, Becker & Fang 1982). Similarly, stars
outside the theoretical grid for dwarfs (U-G > 3.0), but whose colors match
the predicted synthetic loci for normal population I red giants (Buser 1978a),
are classified as such. In either case, these stars are assigned absolute
magnitudes
(Buser 1981).
Objects far outside the theoretical calibrations in the two-color diagrams are either classified as "white objects" (open circles), or are left unclassified (plus signs); both these categories are excluded from the subsequent analysis of the density and luminosity functions.
Comparison with the local luminosity function based on the trigonometric
parallax catalog of nearby stars by Gliese (1969) then provides the crucial
consistency check: if the two disagree substantially and systematically, an
iteration cycle is started by reassigning permissible alternative absolute
magnitudes to an
appropriately chosen number of suitable stars in such a way as to assimilate
the resulting local luminosity function to the Gliese standard.
Copyright The European Southern Observatory (ESO)