The rebrightening of planetary nebulae through ISM interaction

TL;DR

This paper reviews how planetary nebulae interact with the interstellar medium, leading to rebrightening phenomena and resulting in highly disrupted nebulae, with a focus on observational evidence and progenitor structures.

Contribution

It provides the first detailed review of rebrightening in planetary nebulae due to ISM interaction, emphasizing observational examples and progenitor bow shock evidence.

Findings

Rebrightening occurs when PNe interact with pre-existing bow shocks.

Sh 2-68 may be the only well-documented case of a highly disrupted PN.

Progenitors often show evidence of bow shock structures.

Abstract

The interaction of planetary nebulae (PNe) with the interstellar medium as they move through it is now acknowledged to be a major shaping effect not just for ancient and large PNe, but also for relatively young PNe with high speed central stars. The most common effect is a rebrightening as the PN shell interacts with a pre-existing bow shock structure formed during the previous evolutionary phase of the central star. In this review, we consider this rebrightening in detail for the first time and discuss its origins, highlighting some observed examples. We go on to discuss the AGB star progenitors, reviewing the evidence for bow shock structures, and consider the progeny of rebrightened PNe - strongly disrupted objects which bear very little resemblance to typical PNe. Sh 2-68 is inferred to be perhaps the only documented case so far of such a PN.