GALEX and Optical Light Curves of EF Eridanus During a Low State: the Puzzling Source of UV Light

Paula Szkody, Thomas E. Harrison, Richard M. Plotkin, Steve B. Howell, Mark Seibert, Luciana Bianchi

Published 2006-06-21Version 1

Low state optical photometry of EF Eri during an extended low accretion state combined with GALEX near and far UV time-resolved photometry reveals a source of UV flux that is much larger than the underlying 9500K white dwarf, and that is highly modulated on the orbital period. The near UV and optical light curves can be modeled with a 20,000K spot but no spot model can explain both the large amplitude FUV variations and the SED. The limitations of limb darkening, cyclotron and magnetic white dwarf models in explaining the observations are discussed.