Removing the photon-centroiding hole in optical stellar interferometry

Abstract

We describe a technique to remove the photon-centroiding hole from event-sensitive intensified cameras. This effect degrades the average power-spectrum of short-exposures and can bias the fringe visibility estimates from a long baseline stellar interferometer. Using a simple numerical model and 2D interpolating techniques we show that this hole can be corrected directly from actual interferograms on the object itself. We apply our technique to stars with different visual magnitudes, i.e. different photon rates, which have been observed by the GI2T interferometer. The proposed method can significantly improve the GI2T observations providing robust estimates of visibilities whatever the photon rate in clipped short exposures.