Mass Transfer in Two Post-AGB Binaries with Dusty Disks

Abstract

Abstract We present a time series of high-resolution spectra for two poorly studied candidate post-AGB stars surrounded by dusty disks, BD+46 442 and IRAS 19135+3937. We find that both stars show radial velocity variations with periods of 130-140 days. IRAS 19135+3937 has been previously classified as a semi-regular variable based on the light variations with a similar period, but our spectra reveal an evolved star which is too warm to be on the AGB. the variability of BD+46 442 has not been studied till now. the stars reveal a number of spectroscopic peculiarities that resemble features in the interactive binaries including the S-type Symbiotics. Namely, H profile alternates between a double-peak emission and a P Cyg profile, which correlates with the radial velocity phase. A weak asymmetry is tentatively detected in the cross-correlation function that moves in anti-phase with the main component. In addition, strong photospheric lines reveal a narrow central absorption. We conclude that these peculiarities are consistent with a picture where the observed post-AGB stars orbit a much fainter companion at a sub-AU separation and transfer mass on it. the companion is surrounded by an accretion disk, possibly with some kind of an outflow. the SED shows that whole system is surrounded by stable dusty disk as well. It remains to be seen with more observations how much of the line asymmetry could be due to the contribution of low-amplitude pulsations.