Diffraction-limited 76mas speckle masking observations of the core of NGC 1068 with the SAO 6m telescope

We present the first K-band bispectrum speckle interferometry of NGC1068 with an angular resolution of 76mas ( ~ 5.5pc). This angular resolution allows us to attribute the measured flux to only one of the nuclear sources seen at radio wavelengths. The observed decreasing visibility function suggests that the dominant central core is probably not an unresolved point source, but slightly resolved with a FWHM diameter of ~ 30mas ~ 2pc for an assumed Gaussian intensity distribution. This 30mas object is possibly the nuclear torus and/or a scattering halo. We discuss different contributions to the observed K band flux. Between 5GHz and the K-band the spectrum of this component is close to a nu (1/3) proportionality. In addition to the standard interpretation of a hot dust torus surrounding the nucleus of NGC1068, one cannot exclude the possibility that a sizeable fraction of the nuclear flux reaches us via a scattering halo. This then would allow us to determine physical parameters of the nuclear source. Based on data collected at the Special Astrophysical Observatory, Russia