Jet creation in post-AGB binaries: the circum-companion accretion disk around BD+46°442^⋆,⋆⋆

¹ Instituut voor Sterrenkunde (IvS), KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
e-mail: dylan.bollen@kuleuven.be
² Department of Physics & Astronomy, Macquarie University, Sydney, NSW 2109, Australia
³ Astronomy, Astrophysics and Astrophotonics Research Centre, Macquarie University, Sydney, NSW 2109, Australia

Received: 3 July 2017
Accepted: 28 July 2017

Abstract

Aims. We aim at describing and understanding binary interaction processes in systems with very evolved companions. Here, we focus on understanding the origin and determining the properties of the high-velocity outflow observed in one such system.

Methods. We present a quantitative analysis of BD+46°442, a post-AGB binary that shows active mass transfer that leads to the creation of a disk-driven outflow or jet. We obtained high-resolution optical spectra from the HERMES spectrograph, mounted on the 1.2 m Flemish Mercator Telescope. By performing a time-series analysis of the Hα profile, we identified the different components of the system. We deduced the jet geometry by comparing the orbital phased data with our jet model. In order to image the accretion disk around the companion of BD+46°442, we applied the technique of Doppler tomography.

Results. The orbital phase-dependent variations in the Hα profile can be related to an accretion disk around the companion, from which a high-velocity outflow or jet is launched. Our model shows that there is a clear correlation between the inclination angle and the jet opening angle. The latitudinally dependent velocity structure of our jet model shows a good correspondence to the data, with outflow velocities higher than at least 400 km s^-1. The intensity peak in the Doppler map might be partly caused by a hot spot in the disk, or by a larger asymmetrical structure in the disk.

Conclusions. We show that BD+46°442  is a result of a binary interaction channel. The origin of the fast outflow in this system might be to a gaseous disk around the secondary component, which is most likely a main-sequence star. Our analysis suggests that the outflow has a rather wide opening angle and is not strongly collimated. Our time-resolved spectral monitoring reveals the launching site of the jet in the binary BD+46°442. Similar orbital phase-dependent Hα profiles are commonly observed in post-AGB binaries. Post-AGB binaries provide ideal test beds to study jet formation and launching mechanisms over a wide range of orbital conditions.