A peculiar interacting Be star binary in the Small Magellanic Cloud

TL;DR

This study identifies a peculiar Be star binary in the Small Magellanic Cloud exhibiting periodic outbursts and long-term variability, suggesting complex mass transfer phenomena in the system.

Contribution

It reports the discovery and detailed analysis of a unique Be star binary with unusual light curve patterns and spectral features indicating periodic mass transfer.

Findings

Periodic outbursts every 141.45 days observed.

Long-term variability over 2500 days detected.

Spectral evidence of mass transfer at maximum light.

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.