HIGH-RESOLUTION IMAGING OF THE BIPOLAR NEBULA RED-RECTANGLE - EVIDENCE FOR UNSTABLE MASS-TRANSFER IN A CLOSE BINARY-SYSTEM

We present the first diffraction-limited speckle-masking bispectrum ob servations of the central part of the Red Rectangle at optical wavelen gths (lambda similar to 656 nm and lambda similar to 800 nm). The resu lts confirm infrared observations which show that the object is a bipo lar nebula. The dark lane separating the two lobes is probably produce d by an obscuring dust disk slightly inclined with respect to the line of sight. The fainter northern lobe appears not to be reddened by the disk. This implies an upper limit of the outer disk radius of about 2 00 AU. We propose that the observed nebula is the result of recent mas s ejection induced by unstable mass transfer from an AGB star to a clo se companion.