Tracing accretion variability of high-mass YSOs via light echoes

TL;DR

This study investigates the variability of high-mass young stellar objects (HMYSOs) through light echoes in scattered infrared light, aiming to understand accretion processes and their relation to maser activity.

Contribution

It introduces a novel approach to trace HMYSO variability via light echoes in scattered light, linking infrared brightness changes with maser flux density.

Findings

Detected variability in scattered light around HMYSOs.

Observed correlation between maser flux and infrared brightness.

Presented early results on eruptive HMYSO S255IR-NIRS3.

Abstract

There is growing evidence for disk-mediated accretion being the dominant mode of star formation across nearly the whole stellar mass spectrum. The stochastic nature of this process has been realized which implies an inherent source variability. It can be traced more easily for low-mass YSOs (LMYSOs) since high-mass YSOs (HMYSOs) are still embedded even when reaching the ZAMS. While variable reflection nebulae around LMYSOs were among the earliest signs of star formation, little is known on the variability of scattered light from embedded clusters, the birthplaces of HMYSOs. Since the few most massive stars dominate this emission, their variability is literally reflected in scattered light. Moreover, because of their high luminosity, for a given ambient dust density and source distance, the associated nebulosities are much larger than those of LMYSOs. In this case, the light travel time becomes substantial. So the apparent brightness distribution constitutes a light echo, shaped by both the HMYSO variability history and the spatial distribution of the scattering medium. We report on early results of a NIR variability study of HMYSOs associated with Class II methanol masers which aims at revealing a possible correlation between maser flux density and infrared brightness. Additionally, relevant findings for the eruptive HMYSO S255IR-NIRS3 are presented.