Oxygen-rich Mira variables: near-infrared luminosity calibrations. Populations and period-luminosity relations

Abstract

HIPPARCOS astrometric and kinematical data of oxygen-rich Mira variables are used to calibrate absolute near-infrared magnitudes and kinematic parameters. Two sets of near-infrared magnitudes compiled from different authors are used: broad-band K and narrow-band photometric measurements at 1.04 micron (104 filter). Three distinct classes of stars with different kinematics and scale height have been identified. The two most significant groups present characteristics close to the ones usually assigned to extended/thick disk-halo population and old disk population respectively, and thus they might differ by their metallicity abundance. They exhibit different period distributions, as expected if these two groups actually correspond to populations of distinct initial masses, ages and metallicities. Two parallel period-luminosity relations are found in K as well as in 104, one for each significant population. The shift between these relations is interpreted as the consequence of the effects of metallicity abundance on the luminosity.