Impulsive Ejection of Gas In Bipolar Planetary Nebulae

Abstract

We simulate the formation of bipolar planetary nebulae (PNe) through very short impulsive mass ejection events from binary systems, where the asymptotic giant branch (AGB) star ejects a mass shell that is accelerated by jets launched from a compact companion. The acceleration process takes place at very short distances from the binary system, such that the photon-diffusion time is long enough to prevent rapid cooling of the shocked jets' material. When the shocked jets' gas density is lower than the shell density the flow becomes Rayleigh-Taylor unstable and dense clumps are formed in the flow. At later times a PN with clumpy lobes that have a linear distance-velocity relation will be observed. This process might account for the formation of bipolar PNe with clumpy lobes, such as NGC 6302. The energy radiated during the months to years duration of such an event will appear as an intermediate-luminosity optical transient (ILOT)