The carbon star mystery: forty years later

TL;DR

This paper reviews the progress made over forty years in understanding the discrepancy between theoretical models and observations of AGB carbon stars, highlighting advances and future directions.

Contribution

It provides a comprehensive review of the developments in modeling and observations of carbon stars since 1981, summarizing current understanding and future prospects.

Findings

Refined stellar models have improved understanding of carbon star formation.

Observational constraints have increased, narrowing the discrepancy.

Future research directions are outlined for resolving remaining issues.

Abstract

In 1981 Icko Iben Jr published a paper entitled 'The carbon star mystery: why do the low mass ones become such, and where have all the high mass ones gone?', where he discussed the discrepancy between the theoretical expectation and its observational counterpart about the luminosity function of AGB carbon stars. After more than 40 years, our understanding of this longstanding problem is greatly improved, also thanks to more refined stellar models and a growing amount of observational constraints. In this paper we review the state of the art of these studies and we briefly illustrate the future perspectives.