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

Abstract

ABSTRACT Using simultaneous optical and infrared light curves of disc-bearing young stars in NGC 2264, we perform the first multiwavelength structure function study of YSOs. We find that dippers have larger variability amplitudes than bursters and symmetric variables at all time-scales 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 time-scales 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 time-scale 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 on to these YSOs roughly follows a random-walk.