Variability of Hα emission in young stellar objects in the cluster IC 348

H_α emission is one of the most prominent features of young stellar objects in the optical range, and importantly, the equivalent width (EW) of H_α emission [EW(H_α)] is used to characterise an evolutionary stage of young stars. The aim of this work is to identify and study the stellar objects with variable EW(H_α) in the young stellar cluster IC 348. We performed photometric and slit-less observations at several epochs in order to reveal the variable objects. Significant variability of EW(H_α) was found in 90 out of 127 examined stars. From all epochs of observations, 32 objects were classified as CTT (classical T Tauri) and 69 as WTT (weak-line T Tauri) objects. The fraction of the variables in these samples is 60%. We also identified 20 stellar objects, which showed not only a significant variability of the EW, but which also change their apparent evolutionary stage (CTT ⇆ WTT). For six stars, H_α line was observed in both emission and absorption.