Alain Chelli
Laboratoire d'Astrophysique de Grenoble

Abstract
We provide a complete theory of the phase closure of a binary system in which a small, feeble and unresolved companion acts as a perturbing parameter on the spatial frequency spectrum of a dominant, bright, resolved source.  We demonstrate that the influence of the companion can be measured with precision by measuring the phase closure of the system near the nulls of the primary visibility function. In these regions of phase closure nulling, there always exists frequency intervals where the phase closure signature of the companion is larger than any systematic error and hence can be measured. We show that this technique allows to retrieve many astrophysically relevant properties of faint and close companions such as flux, position, and, in favorably cases, spectrum. We conclude by a rapid study of the potentialities of phase closure nulling observations with current interferometers and explore the requirements for a new type of dedicated instrument.

2008 November 06, 14:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto