Towards an understanding of YSO variability: A multi-wavelength analysis of bursting, dipping, and symmetrically varying light curves of disc-bearing YSOs

Abstract

Using simultaneous optical and infrared light curves of disc-bearing young stars in NGC 2264, we perform the first multi-wavelength structure function study of YSOs. We find that dippers have larger variability amplitudes than bursters and symmetric variables at all timescales longer than a few hours. By analysing optical-infrared colour time-series, we also find that the variability in the bursters is systematically less chromatic at all timescales than the other variability types. We propose a model of YSO variability in which symmetric, bursting, and dipping behaviour is observed in systems viewed at low, intermediate, and high inclinations, respectively. We argue that the relatively short thermal timescale for the disc can explain the fact that the infrared light curves for bursters are more symmetric than their optical counterparts, as the disc reprocesses the light from all rotational phases. From this model, we find that the accretion variability onto these YSOs roughly follows a random-walk.