  This study is a contribution in comprehending the role of binarity upon late
stages of stellar evolution. We determine the binary status of six Galactic RV
Tauri stars, namely DY Ori, EP Lyr, HP Lyr, IRAS 17038-4815, IRAS 09144-4933
and TW Cam, which are surrounded by a dusty disc. We also place them on the HR
diagram, thereby establishing their evolutionary nature. All the six Galactic
RV Tauri stars included in this study are binaries with orbital periods ranging
between $\sim$ 650 and 1700 days and with eccentricities between 0.2 and 0.6.
The mass functions range between 0.08 to 0.55 M$_\odot$ which points to an
unevolved low mass companion. In the photometric time series we detect a
long-term variation on the time-scale of the orbital period for IRAS
17038-4815, IRAS 09144-4933 and TW Cam. Our derived stellar luminosities
obtained from a calibrated PLC relation indicates that all except DY Ori and EP
Lyr, are post-AGB stars. DY Ori and EP Lyr are likely examples of the recently
discovered dusty post-RGB stars. The orbital parameters strongly suggest that
the evolution of these stars was interrupted by a strong phase of binary
interaction during or even prior to the AGB. The observed eccentricities and
long orbital periods among these stars provides a challenge to the standard
theory of binary evolution.
