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Previous studies have shown that many post-AGB stars with dusty disks areassociated with single-lined binary stars. To verify the binarity hypothesis ona larger sample, we started a high-resolution spectral monitoring of about 40field giants, whose binarity was suspected based on either a light curve, aninfrared excess, or a peculiar chemical composition. Here we report on thediscovery of the periodic RV variations in BD+46 442, a high-latitude F giantwith a disk. We interpret the variations due to the motion around a faintcompanion, and deduce the following orbital parameters: Porb = 140.77 d, e =0.083, asini=0.31 AU. We find it to be a moderately metal-poor star([M/H]=-0.7) without a strong depletion pattern in the photospheric abundances.Interestingly, many lines show periodic changes with the orbital phase: Halphaswitches between a double-peak emission and a PCyg-like profiles, while strongmetal lines appear split during the maximum redshift. Similar effects arelikely visible in the spectra of other post-AGB binaries, but their regularityis not always realized due to sporadic observations. We propose that thesefeatures result from an ongoing mass transfer from the evolved giant to thecompanion. In particular, the blue-shifted absorption in Halpha, which occursonly at superior conjunction, may result from a jet originating in theaccretion disk around the companion and seen in absorption towards the luminousprimary.

Time resolved spectroscopy of BD+46 442: gas streams and jet creation in a newly discovered evolved binary with a disk