Globular clusters and the Mira period-luminosity relation

Abstract

A globular cluster distance scale based on Hipparcos parallaxes of subdwarfs has been used to derive estimates of M_K for cluster Miras, including one in the Small Magellanic Cloud (SMC) globular cluster NGC 121. These lead to a zero-point of the Mira infrared period-luminosity (PL) relation, PL(K), in good agreement with that derived from Hipparcos parallaxes of nearby field Miras. The mean of these two estimates together with data on LMC Miras yields a Large Magellanic Cloud (LMC) distance modulus of 18.60+/-0.10 in evident agreement with a metallicity-corrected Cepheid modulus (18.59+/-~0.10). The use of luminous asymptotic giant branch (AGB) stars as extragalactic population indicators is also discussed.