A Zwicky Transient Facility Look at Optical Variability of Young Stellar Objects in the North America and Pelican Nebulae Complex

Abstract

We present a study of 323 photometrically variable young stellar objects that are likely members of the North America and Pelican nebulae star-forming region. To do so, we utilize over two years of data in the g and r photometric bands from the Zwicky Transient Facility. We first investigate periodic variability, finding 46 objects (∼15% of the sample) with significant periods that phase well and can be attributed to stellar rotation. We then use the quasiperiodicity ( Q ) and flux asymmetry ( M ) variability metrics to assign morphological classifications to the remaining aperiodic light curves. Another ∼39% of the variable star sample beyond the periodic (low Q ) sources are also flux-symmetric, but with a quasiperiodic (moderate Q ) or stochastic (high Q ) nature. Concerning flux-asymmetric sources, our analysis reveals ∼14% bursters (high negative M ) and ∼29% dippers (high positive M ). We also investigate the relationship between variability slopes in the g versus g − r color–magnitude diagram, and the light-curve morphological classes. Burster-type objects have shallow slopes, while dipper-type variables tend to have higher slopes that are consistent with extinction-driven variability. Our work is one of the earliest applications of the Q and M metrics to ground-based data. We therefore contrast the Q values of high-cadence and high-precision space-based data, for which these metrics were designed, with Q determinations resulting from degraded space-based light curves that have the cadence and photometric precision characteristic of ground-based data.