Flow-Based Generative Emulation of Grids of Stellar Evolutionary Models

TL;DR

This paper introduces a flow-based generative model to emulate stellar evolutionary model grids, enabling efficient parameter inference and revealing insights into stellar populations and parameter uncertainties.

Contribution

The novel application of conditional normalizing flows to emulate complex stellar model grids and perform Bayesian inference on large asteroseismic datasets.

Findings

Flow models accurately emulate stellar evolutionary tracks and isochrones.

Revised stellar parameters show improved agreement with existing models.

Identified overestimation of masses in previous asteroseismic analyses.

Abstract

We present a flow-based generative approach to emulate grids of stellar evolutionary models. By interpreting the input parameters and output properties of these models as multi-dimensional probability distributions, we train conditional normalizing flows to learn and predict the complex relationships between grid inputs and outputs in the form of conditional joint distributions. Leveraging the expressive power and versatility of these flows, we showcase their ability to emulate a variety of evolutionary tracks and isochrones across a continuous range of input parameters. In addition, we describe a simple Bayesian approach for estimating stellar parameters using these flows and demonstrate its application to asteroseismic datasets of red giants observed by the Kepler mission. By applying this approach to red giants in open clusters NGC 6791 and NGC 6819, we illustrate how large age uncertainties can arise when fitting only to global asteroseismic and spectroscopic parameters without prior information on initial helium abundances and mixing length parameter values. We also conduct inference using the flow at a large scale by determining revised estimates of masses and radii for 15,388 field red giants. These estimates show improved agreement with results from existing grid-based modelling, reveal distinct population-level features in the red clump, and suggest that the masses of Kepler red giants previously determined using the corrected asteroseismic scaling relations have been overestimated by 5-10%.