Flow-Based Generative Emulation of Grids of Stellar Evolutionary Models
This work addresses the challenge of efficiently modeling stellar evolution for astrophysics, though it is incremental as it adapts existing flow-based methods to a specific domain.
The authors tackled the problem of emulating complex stellar evolutionary models by developing a flow-based generative approach that learns conditional joint distributions between input parameters and output properties, enabling continuous emulation of evolutionary tracks and isochrones. They applied this method to red giants, showing that it improves mass and radius estimates, reveals population-level features, and indicates a 5-10% overestimation in previous mass determinations.
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%.