A Parameterized YSO Accretion Disk Model with Increasing Accretion Rate: Predicted Outburst Lightcurves

TL;DR

This paper presents a parametric model for FU Ori type star outbursts, simulating multi-band light curves to understand accretion disk evolution and star-disk interactions during outbursts.

Contribution

It introduces a time-dependent accretion rate model coupled with multiple disk components to predict outburst light curves across different wavelengths.

Findings

Optical and near-infrared lightcurves mirror the accretion profile, sensitive to shocks and inner gas disk heating.

Mid-infrared lightcurves respond to the innermost dust disk's location and heating.

The model provides insights into the flux dominance of different components during outbursts.

Abstract

A sub-class among Young Stellar Objects (YSOs), known as FU Ori type stars, undergo sudden rises in luminosity by several orders of magnitude on timescales of a few months to a few years, and decay back to quiescence on timescales of a few decades. Modelling the light curves of these objects is crucial to understanding how different components of these accretion disk systems evolve during outburst. For this purpose, we use a parametric model that couples the stellar photospheric emission, magnetospheric accretion shocks, an irradiated dust disk, and a viscously heated gas disk. We adopt time-dependent accretion rate profiles that mimic the observed morphologies of FU Ori outburst light curves, and we use the accretion model infrastructure to simulate multi-band light curves, as well as color curves. The model enables us to study how different components dominate the flux in each band over the course of an outburst, providing insight into star-magnetosphere-disk interactions throughout the outburst cycle. We find that throughout an accretion outburst, red optical and near-infrared lightcurves generally follow the same or very similar form as the input accretion profile, being sensitive to heating in the accretion shocks and inner gas disk, while mid-infrared lightcurves are more responsive to the location and heating of the innermost dust disk.