OXYGEN-RICH MIRA VARIABLES - NEAR-INFRARED LUMINOSITY CALIBRATIONS - POPULATIONS AND PERIOD-LUMINOSITY RELATIONS

HIPPARCOS astrometric and kinematical data of oxygen-rich Mira variabl es are used to calibrate absolute near-infrared magnitudes and kinemat ic parameters. Two sets of near-infrared magnitudes compiled from diff erent authors are used: broad-band K and narrow-band photometric measu rements at 1.04 mu m (104 filter). Three distinct classes of stars wit h different kinematics and scale height have been identified. The two most significant groups present characteristics close to the ones usua lly assigned to extended/thick disk-halo population and old disk popul ation respectively, and thus they might differ by their metallicity ab undance. They exhibit different period distributions, as expected if t hese two groups actually correspond to populations of distinct initial masses, ages and metallicities. Two parallel period-luminosity relati ons are found in K as well as in 104, one for each significant populat ion. The shift between these relations is interpreted as the consequen ce of the effects of metallicity abundance on the luminosity.