2010A&A...514A..89S

High resolution spectral observations of the polar EF Eridani obtained in a low state with X-Shooter revealed narrow emission lines from the irradiated secondary. The lines were most prominent in the near-IR CaII 8542Å 2-triplet, the more intensive Hα line had additional emission likely originating from an accretion stream. The lines with a radial velocity amplitude, K₂'=385±4km/s, serve as tracer of the otherwise unseen companion. The mass function implies a massive white dwarf with M_wd>0.65M_☉ at 3σ confidence, and a short distance to the binary, d∼111pc (<145pc at 3σ confidence). The spectral energy distribution from the UV to the IR together with the high mass ratio gives further strong evidence of EF Eri being a post period-minimum object with M₂<0.06M_☉.