K-Band Red Clump Distance to the Large Magellanic Cloud

The Hipparcos I-band calibration of horizontal-branch red clump giants as standard candles has lead to controversial results for the distance to the Large Magellanic Cloud (LMC). In an attempt to properly ascertain the corrections for interstellar extinction and clump age and metallicity, we analyze new multiwavelength luminosity functions of the LMC red clump. Our photometry data set in the K band was obtained with the Son of Isaac infrared imager at the European Southern Observatory's New Technology Telescope. In the V and I passbands, we employ data from the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The LMC red clump is first identified in a K, (V-K) color-magnitude diagram. Our luminosity functions yield apparent magnitudes of K = 16.974, I = 18.206, and V = 19.233 (±0.009r ± 0.02s; random and systematic errors, respectively). Compared directly to the Hipparcos red clump calibration (without a correction for age and metallicity), the LMC clump measurements imply a negative interstellar reddening correction. This unphysical result indicates a population difference between clumps. A modified calibration based on theoretical modeling yields an average reddening correction of E(B-V) = 0.089 ± 0.015r and a true LMC distance modulus of μ0 = 18.493 ± 0.033r ± 0.03s. We reconcile our result with the short distance previously derived from OGLE II red clump data.