Paper:	The Distance Scale to Globular Clusters
Volume:	167, Harmonizing Cosmic Distance Scales in a Post-Hipparcos Era
Page:	140
Authors:	Cacciari, Carla
Abstract:	We review the most common methods used to derive the distance to galactic globular clusters, with special emphasis to the determinations based on Hipparcos data. From the comparison among the various results the following general conclusions can be drawn: i) the main-sequence fitting method, where Hipparcos parallaxes have brought the most significant improvement, does indeed produce consistent results among the various determinations, within ± 0.15 mag error; and ii) there is still a range of about 0.2-0.3 mag in the distance moduli when all methods are compared: some produce MV(HB) ~ 0.7 mag or fainter at [Fe/H] ~ -1.6 (e.g., statistical parallaxes on RR Lyrae stars, trigonometric parallaxes on HB stars), others produce values that are >= 0.2 mag brighter (e.g., main sequence fitting, RGB bump, tip of the RGB, double-mode pulsators), others produce intermediate values (e.g., direct astrometry, the Baade-Wesselink method), and finally the WD sequence fitting produces contrasting results.

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