Expected FU Ori Outburst Amplitudes from the Optical to the Mid-Infrared

TL;DR

This paper models the expected brightness increase across optical to mid-infrared wavelengths during FU Ori outbursts in young stellar object disks, combining passive and active accretion disk states.

Contribution

It introduces a model predicting outburst amplitudes from optical to mid-infrared wavelengths for FU Ori stars, integrating passive and active disk states.

Findings

Predicted brightness amplitudes vary across wavelengths.

Model captures transition from low to high accretion states.

Results aid in identifying FU Ori outbursts observationally.

Abstract

Disks around young stellar objects (YSOs) consist of material that thermally emits the energy provided by a combination of passive heating from the central star, and active, viscous heating due to mass accretion. FU Ori stars are YSOs with substantially enhanced accretion rates in their inner disk regions. As a disk transitions from standard low-state, to FU Ori-like high-state accretion, the outburst manifests through photometric brightening over a broad range of wavelengths. We present results for the expected amplitudes of the brightening between $\sim$4000 \AA\ and 8 $\mu$m -- the wavelength range where FU Ori type outburst events are most commonly detected. Our model consists of an optically thick passive $+$ active steady-state accretion disk with low and high accretion states.