Absolute magnitudes of M type semi-regular variables in Hipparcos catalogue

Visual absolute magnitudes from Hipparcos parallaxes and photometry have been calculated for M giant irregular (L) and semi-regular (SR, SRa, SRb) variables. Positions in the H-R diagram of the variables with relative parallax error < 0.175 indicate that SRb's tend to be fainter in M-<nu>, bluer in B - V, and later in spectral type than the rest of the variables. Semi-regular variables with periods smaller than 10 days as given in Hipparcos obey a clearly defined period and period - colour relations.