“…A similar conclusion has been independently obtained by David-Uraz et al (2020). Notably, among the eleven magnetic O-type stars with known variation curves,for seven stars, HD 108, HD 37022 (= 1 Ori C), HD 54879, HD 148937, HD 191612, Tr 16-22, and NGC 1624-2, only one magnetic pole is visible throughout the rotation cycle (Shultz & Wade 2017;Petit et al 2008;Hubrig et al 2020;Wade et al 2012b;Donati et al 2006;Naze et al 2016, this work). This implies that, due to an unfavorable inclination of the rotation axis, a larger fraction of their surfaces can never be observed, leaving the structure of the field over the invisible surface only constrained by the assumption of a tilted centred dipole.…”