First results from HIPPARCOS trigonometrical parallaxes of Mira-type variables

HIPPARCOS trigonometrical parallaxes are given for pre selected Mira variables Linear diameters are derived for oxygen rich Miras with known angular diameters Comparison with pulsation theory shows that two of them both with periods over day are fundamental pulsators the others all with periods less than day pulsate in an overtone The Mira PL relations in MK and Mbol are calibrated for oxygen rich overtone pulsators adopting slopes for these relations from LMC data A mean LMC distance modulus of is derived this is very close to that of derived from the Cepheids The uncertainty in the value derived from the Miras is estimated to be less than mag The absolute magnitude of the only carbon rich Mira in the sample R Lep period of day indicates that it is a fundamental pulsator Other stars discussed individually are the symbiotic Mira R Aqr the double period Mira R Cen and two Miras with decreasing periods R Aql and R Hya