PROFESSOR M. PARTHASARATHY

Far-infrared surveys and multi-wavelength follow-up studies have revealed few hundred post-AGB supergiants with circumstellar dust shells/disks and molecular envelopes. Study of these stars is enabling us to further understand the advanced stages of evolution of low and intermediate mass stars. These post-AGB supergiants are found to form an evolutionary sequence in the transition region in the H-R diagram from the tip of the AGB into early stages of planetary nebulae. Some of the A-type post-AGB supergiants were found to show extreme depletion of refractory elements in their photospheres. All the F-type post-AGB supergiants with 21-micron emission feature were found to be overabundant in carbon and s-process elements indicating that they have evolved from the carbon star stage on the AGB. The chemical composition of hot post-AGB stars indicate that they left the AGB before the third dredge-up. We found few hot post-AGB stars which are rapidly evolving into early stages of young planetary nebulae.