The de-censoring of the faint stars in TYCHO photometry.
Grenon, M.; Hog, E.; Halbwachs, J. L.; Wicenec, A.; Grossmann, V.; di Meo, T.
France, Switzerland, Germany, Denmark
Abstract
The Tycho catalogue provides astrometric and photometric data for more than 1 million stars. The derivation of the mean magnitudes of stars fainter than about 8mag required a dedicated treatment, in order to take into account the observations that were too faint for providing a measurable signal. This treatment, called "de-censoring", is based on a statistical model permitting to substitute mean values to the missing data. Faint photometric standard stars are used to demonstrate that the de-censoring produces reliable magnitudes and uncertainties.