Phase-Resolved Infrared H- and K-band Spectroscopy of EF Eridani

Abstract

We present new phase-resolved H and K-band spectroscopy of the ultra-short period magnetic cataclysmic variable EF Eri in its current, prolonged ``low'' state obtained using NIRI on Gemini-North, and NIRSPEC on Keck II. These new data show that the H-band spectrum of EF Eri appears to be dominated by cyclotron emission during the entire orbital cycle. The {\it K}-band spectrum of EF Eri is likewise dominated by cyclotron emission during most of an orbital period, but near binary phase 0.0, the secondary star spectrum may be visible. We conclude that strong, and highly variable cyclotron emission is responsible for the photometric variation previously reported for EF Eri. The nature of this cyclotron emission is complex: the H-band spectra show that the dominant cyclotron harmonic at phase 0.5 peaks at 1.65 $μ$m, but at phase 0.0, the harmonic peaks near 1.72 $μ$m. At phase 0.5, there is another cyclotron feature present that peaks in between the H and K bands (near 1.93 $μ$m), but at phase 0.0, no such feature is present. These data suggest that cyclotron emission from both poles is occurring.