De-biasing interferometric visibilities in VLTI-AMBER data of low SNR observations

AIMS: We have found that the interferometric visibilities of VLTI-AMBER observations, extracted via the standard reduction package, are significantly biased when faint targets are concerned. The visibility biases derive from a time variable fringing effect (correlated noise) appearing on the detector. METHODS: We have developed a method to correct this bias that consists in a subtraction of the extra power due to such correlated noise, so that the real power spectrum at the spatial frequencies of the fringing artifact can be restored. RESULTS: This pre-processing procedure is implemented in a software, called AMDC and available to the community, to be run before the standard reduction package. Results obtained on simulated and real observations are presented and discussed.