A primer on the formation and evolution of hydrogen deficient Central Stars of Planetary Nebul{\ae} and Related Objects

TL;DR

This paper reviews the formation and evolution of hydrogen-deficient central stars of planetary nebulae, detailing observable features, classifications, progenitors, and evolutionary scenarios including single and binary models.

Contribution

It provides a comprehensive synthesis of observational data, theoretical models, and the role of binary interactions in the formation of hydrogen-deficient central stars.

Findings

Detailed description of observable features and classifications.

Analysis of single and binary evolutionary scenarios.

Discussion of the born again scenario and its uncertainties.

Abstract

We present a brief review on the formation and evolution of hydrogen deficient central stars of planetary nebulae. We include a detailed description of the main observable features of both the central stars and their surrounding nebulae and review their main classifications. We also provide a brief description of the possible progenitor systems of hydrogen deficient central stars, as well as, of transients closely connected to the formation of these stars. In particular we offer a detailed theoretical explanation of the main evolutionary scenarios, both single and binary, devised to explain these stars and nebulae. Particular emphasis is made in the description of the so-called born again scenario, their quantitative predictions and uncertainties. Finally we discuss the pros and cons of both binary and single evolution channels, draw some conclusions and discuss open questions in the field.