Exploration of near-infrared and short-term variability in spectra of planetary nebulae precursors

Summary of the postdoctoral research grant project: Despite planetary nebulae being objects of great astrophysical use and interest, it is poorly understood how they take shape. It is unclear how spherically symmetric nebulae surrounding asymptotic giant branch phase stars become non-spherical upon arrival at the post-asymptotic giant branch stage - an immediate precursor to planetary nebula phase. The poorly understood stellar wind in the post-asymptotic giant branch stage is expected to play a significant role in the morphological change. High-resolution spectroscopy provides a way to investigate physical processes related to the stellar wind formation. Spectral line variability of stars that have recently started post-asymptotic giant branch evolution will be investigated by using spectra acquired with advanced spectrographs. The focus will be on two areas that are virtually unexplored as of yet – variability in the near-infrared and short-term variability. The former will be studied by using already available spectra and will result in a scientific article. Observing time proposals will be prepared to provide additional spectra that will contribute to investigation of both types of variability. By allowing to probe dynamic processes in the region above the stellar surface where the stellar wind forms, such exploration has a potential to improve the knowledge about shaping of planetary nebulae.