Unveiling the nature of the 321 s Orbital Period X – ray source

A nearly simultaneous X-ray/optical (Chandra and VLT) observational campaign of RXJ0806.3+1527 has been carried out during 2001. These observations allowed us to phase the X–ray and optical light curves for the first time. We measured a phase–shift of ∼0.5, in good agreement with the presence of two distinct emission regions and with the X–ray irradiation process predictions. The Chandra data allowed us also to study in details the X-ray spectrum of RXJ0806.3+1527, which is consistent with a soft (kT<70 eV) and small (RBB <20 km) blackbody component. We discuss the present findings on the light of the models proposed so far to account for the X–ray emission detected from RXJ0806.3+1527, and its twin source RXJ1914.4+2456.