Gaia astrometry was used to explore the properties of Galactic Post-AGB stars in the literature. DR3 precise parallaxes allowed us to isolate a small group of stars in the direction of the Large Magellanic Cloud (LMC) previously reported as post-AGB stars in the LMC, but that, according to their distances, seem to be located in an intermediate region between the LMC and the Galaxy. In order to verify this, we have used a classifier that allows us to evaluate the probability of a star belonging to the Milky Way (MW) or the LMC. This classifier is based on an Artificial Neural Network (ANN) algorithm and is fed with the astrometry and photometry published in DR3. In this presentation, we study the membership probabilities of several samples of stars in the direction of the LMC. As a result, we have obtained that around 25-30% of stars in our samples, suspected to belong to the LMC, have indeed low probabilities of belonging to either one galaxy or the other. On the contrary, they seem to be located in an intermediate region between the two galaxies. We also analysed the radial velocity distributions of the different samples and the location of the stars in a colour-magnitude diagram. APOGEE data was also used to study the chemical abundances of stars in the different regions (LMC, MW, and intermediate population).

V510 Pup (IRAS 08005-2356) is a binary post-AGB system with a fast molecular outflow that has been noted for its puzzling mixture of carbon- and oxygen-rich features in the optical and infrared. To explore this chemical dichotomy and relate it to the kinematics of the source, we present an ACA spectral line survey detailing fourteen newly detected molecules in this pre-planetary nebula. The simultaneous presence of CN/C2H/HC3N and SO/SO2 support the previous conclusion of mixed chemistry, and their line profiles indicate that the C- and O-rich material trace distinct velocity structures in the outflow. This evidence suggests that V510 Pup could harbor a dense O-rich central waist from an earlier stage of evolution, which persisted after a fast C-rich molecular outflow formed. By studying the gas phase composition of this unique source, we aim to reveal new insights into the interplay between dynamics and chemistry in rapidly evolving post-AGB systems.

Water fountains (WFs) are thought to represent an early stage in the morphological evolution of circumstellar envelopes surrounding low- and intermediate-mass evolved stars. These objects are considered to transition from spherical to asymmetric shapes. Despite their potential importance in this transformation process of evolved stars, there are only a few known examples. To identify new WF candidates, we used databases of circumstellar OH (1612 MHz) and H2O (22.235 GHz) maser sources, and compared the velocity ranges of the two maser lines. Finally, 41 sources were found to have a velocity range for the H2O maser line that exceeded that of the OH maser line. Excluding known planetary nebulae and after reviewing the maser spectra in the original literature, we found for 11 sources the exceedance as significant, qualifying them as new WF candidates.

This review presents the latest advances in the nebular studies of post-AGB objects. Post-AGB stars are great tools to test nucleosynthesis and evolution models for stars of low and intermediate masses, and the evolution of dust in harsh environment. I will present the newly discovered class of post-RGB stars, formed via binary interaction on the RGB. Binary systems can also lead to the formation of two class of aspherical post-AGB, the Proto-Planetary Nebulae and the naked post-AGBs (dusty RV Taus, a.k.a. Van Winckel’s stars).

A review is given of the properties of post-AGB stars. Methods to find candidate post-AGB stars are briefly discussed, along with some results and selection effects involved. Their photospheric parameters (Teff , log g, abundances), energy distributions and binarity are also discussed. Evidence for mass loss, both past and present, is reviewed.