Withdrawn as Duplicate: Testing the magnetar scenario for superluminous supernovae with circular polarimetry. - Cikota, Aleksandar; Leloudas, Giorgos; Bulla, Mattia; Inserra, Cosimo; Chen, Ting-Wan; Spyromilio, Jason; Patat, Ferdinando; Cano, Zach; Cikota, Stefan; Coughlin, Michael W; Kankare, Erkki; Lowe, Thomas B; et al. (Monthly Notices of the Royal Astronomical Society: Letters, 2019)