We present here a new observational technique, Phase Closure Nulling (PCN),
which has the potential to obtain very high contrast detection and spectroscopy
of faint companions to bright stars. PCN consists in measuring closure phases
of fully resolved objects with a baseline triplet where one of the baselines
crosses a null of the object visibility function. For scenes dominated by the
presence of a stellar disk, the correlated flux of the star around nulls is
essentially canceled out, and in these regions the signature of fainter,
unresolved, scene object(s) dominates the imaginary part of the visibility in
particular the closure phase. We present here the basics of the PCN method, the
initial proof-of-concept observation, the envisioned science cases and report
about the first observing campaign made on VLTI/AMBER and CHARA/MIRC using this
technique.Comment: To be published in the proceedings of the SPIE'2010 conference on
"Optical and Infrared Interferometry II
