Characterizing the Relationship between the Binary Fraction and Metallicity in the Magellanic Clouds

Binary systems are a common byproduct of the stellar evolution process, but much about their formation remains poorly understood. Of particular interest is the relationship between the close binary fraction and metallicity, which offers insight into a variety of important processes, including accretion, proto-binary fragmentation, type Ia supernovae progenitor rates, and the chemical evolution of galaxies. This relationship has been continuously debated over the last three decades, with several independent studies reaching conflicting results. However, recent work by Moe et al. (2019) appears to have made significant strides towards resolving this discrepancy by re-examining five prior studies on this topic. By applying additional corrections for incompleteness, Moe et al. showed that all five studies could be made to agree on a single conclusion: the close binary fraction is strongly anti-correlated with metallicity. In this work, we present a test of Moe et al.’s hypothesis based on data from the Magellanic Clouds. As the average metallicity of the Large Magellanic Cloud (LMC) is roughly two-and-a-half times the average metallicity of the Small Magellanic Cloud (SMC), our test consists of a straightforward comparison of the close binary fractions in each galaxy. Approximately 380,000 light curves from each galaxy were transformed into two-dimensional images that represent information about the shape of the light curves via “dm-dt” mappings as described in Mahabal et al. (2017). These images were then fed into a convolutional neural network (CNN) that had been trained on a combination of simulated images and a small set of real, identified images. The CNN was able to identify binary objects with an accuracy rate of approximately 94%. After additional visual verification of the final binary sets, the binary fractions in both galaxies were computed and compared. We will report preliminary results on the relative LMC/SMC binary fraction.