A peculiar interacting Be star binary in the Small Magellanic Cloud

Abstract

We find that the emission line object OGLEJ005039.05-725751.4, a member of the cluster OGLE-CL SMC 64, exhibits a peculiar light curve pattern repeating with a recurrence time of 141.45 days. The light curve resembles periodic outbursts with a duty cycle of 20%. A second long-cycle of 2500 days is also detected in the photometric dataset. Two X-SHOOTER spectra obtained at minimum and maximum reveal a Be star dominating at minimum light resembling the Classical Be star 48 Lib. The larger H$\alpha$ emission, the stronger NaD absorption and the appearance of emission in the infrared Ca II triplet at maximum, might indicate periodic mass transfer in a complex binary system.