A Bound on the Light Emitted During the TP-AGB Phase

TL;DR

This paper establishes a lower limit on the light emitted during the TP-AGB phase by linking core mass growth to energy output, providing insights into helium enrichment and stellar yields in population models.

Contribution

It introduces a method to constrain TP-AGB luminosity using core mass growth and stellar models, improving understanding of stellar yields and population synthesis.

Findings

Core mass growth during TP-AGB is about 20% for 2-3.5 Msun stars.

Approximately half of the TP-AGB energy output is due to core growth.

Current models' yields are estimated as a function of initial stellar mass.

Abstract

The integrated luminosity of the TP-AGB phase is a major uncertainty in stellar population synthesis models. We use the white dwarf initial final mass relation and stellar interiors models to demonstrate that a significant fraction of the core mass growth for intermediate (1.5 < Msun < 6) mass stars takes place during the TP-AGB phase. We find evidence that the peak fractional core mass contribution for TP-AGB stars is ~20% and occurs for stars between 2 Msun and 3.5 Msun. Using a simple fuel consumption argument we couple this core mass increase to a lower limit on the TP-AGB phase energy output. Roughly half of the energy released in models of TP-AGB stars can be directly accounted for by this core growth; while the remainder is predominantly the stellar yield of He. A robust measurement of the emitted light in this phase will therefore set strong constraints on helium enrichment from TP-AGB stars, and we estimate the yields predicted by current models as a function of initial mass. Implications for stellar population studies and prospects for improvements are discussed.