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Published online by Cambridge University Press: 07 August 2017
We wish to explore the hypothesis that the shells and halos of planetary nebulae are formed during the thermal pulsing of progenitor AGB stars. Using published data and model results we compare the AGB interpulse time ΔtT and the time between shell ejections ΔtD for a sample of PNe with halos. ΔtT is derived from the Paczynski relation using the PNe central star luminosity. ΔtD is calculated using the radii and velocity of PNe shells and halos.