ZTF long-term (top left) and phase-folded (top right) light curves in g, r, and i filters and the DBSP optical spectrum of 2CXO J123727.5+655211 (bottom). The gray lines represent the Keck Telluric Line List. The optical spectrum shows hydrogen, helium, and high-excitation He II 4686 Å emission lines, giving a line ratio of He II/Hβ ≈ 0.37 (see Table 3). Together with optical light curves, this indicates that the object is a polar (see Sect. 5.1.3 for more details).