Rebrightening of Planetary Nebulae Through Interaction with the Interstellar Medium

摘要

Abstract: The interaction of planetary nebulae (PNe) with the interstellar medium (ISM) as they moventhrough it is now acknowledged to be a major shaping effect not just for ancient and large PNe, but also fornrelatively young PNe with high-speed central stars. The most common effect is a rebrightening as the PNnshell interacts with a pre-existing bow-shock structure formed during the previous evolutionary phase of thencentral star. In this review we consider this rebrightening in detail for the first time and discuss its origins,nhighlighting some observed examples.We go on to discuss theAGB progenitor stars, reviewing the evidencenfor bow-shock structures, and consider the progeny of rebrightened PNe—strongly disrupted objects whichnbear very little resemblance to typical PNe. Sh 2-68 is inferred to be perhaps the only documented case so farnof such a PN.