We have explored the effect of transition timescales in planetary nebulae (PNe) formation. We have performed hydrodynamical simulations of the evolution of the stellar winds predicted by theoretical stellar evolutionary models adopting two choices for the evolution during the transition time. The evolution of the star from the AGB to the PN stage

We have obtained high-resolution high signal-to-noise ratio spectra of the S I near-infrared doublet at 8694 Å in eight metal-poor stars with metallicities in the range -0.6

IRAS 10215-5916 was classified as a post-AGB star and also as a massive red supergiant. It was also found to be a spectroscopic binary. In our high resolution spectra we found molecular features from a cool star of Teff = 3750K. We also see the spectral signature of a relatively hotter star of Teff = 7250K. We found that both the components of the

HD 331319 is a F3 Ib star with a detached cold circumstellar dust shell with far-IR colours similar to planetary nebulae. From an analysis of high resolution spectra using LTE stellar atmospheric models, we have derived the atmospheric parameters and the chemical composition of HD 331319. By matching the theoretical and the observed spectrum we

In the high resolution optical spectra we identified forbidden lines of [OI] and [CI], which indicate the presence of low excitation nebula. There are many emission lines due forbidden and permitted lines of neutral and singly ionised metals. The Hα, FeII 6383Å, NaI D1, D2 lines and the CaII IR triplet lines show P-Cygni profiles indicating a mass

HD 168625 (B9-A0 Ia) was classified as a post-AGB star and also as a luminous blue variable. We have analysed the high resolution optical spectra of HD 168625 and derived the atmospheric parameters and the chemical composition. We obtained Teff = 15000K, log g = 2.5, xit = 6km/s and [M/H] = 0.0, and estimated the chemical composition. We find [C/H]