The Lutz-Kelker Paradox

TL;DR

The paper critically examines the Lutz-Kelker correction, revealing it does not provide unbiased estimates for individual stellar parallaxes and highlighting its limitations for interpreting data from Gaia and Hipparcos.

Contribution

It demonstrates that the Lutz-Kelker correction is inappropriate for individual stars and offers a true correction method using numerical and Monte Carlo techniques.

Findings

Lutz-Kelker correction does not unbiasedly estimate individual parallaxes.

Bayesian probability for true parallax is independent of star distribution.

A true correction method is developed and validated.

Abstract

The Lutz-Kelker correction is intended to give an unbiased estimate for stellar parallaxes and magnitudes, but it is shown explicitly that it does not. This paradox results from the application of an argument about sample statistics to the treatment of individual stars, and involves the erroneous use of a frequency distribution in the manner of a probability density function considered as a Bayesian prior. It is shown that the Bayesian probability distribution for true parallax given the observed parallax of a selected star is independent of the distribution of other stars. Consequently the Lutz-Kelker correction should not be used for individual stars. This result has important implications for the RR Lyrae scale and for the interpretation of results from Gaia and Hipparcos. The Lutz-Kelker correction is a poor treatment of the Trumpler-Weaver bias which affects parallax limited samples. A true correction is calculated using numerical integration and confirmed by a Monte Carlo method.