Direct Evidence for a Polar Spot on SV Cam

We have used spectrophotometric data from the Hubble Space Telescope to eclipse-map the primary component of the RS CVn binary SV Cam over 9 HST orbits. We find from these observations and the HIPPARCOS parallax that the surface flux in the eclipsed low-latitude region of the primary is about 30% lower than computed from a PHOENIX model atmosphere at the effective temperature that best fits the spectral energy distribution of the eclipsed flux. This can only be accounted for if about a third of the primary's surface is covered with unresolved dark star-spots. Extending this to the full surface of the primary, we find that even taking into account this spot filling factor there is an additional flux deficit on the primary star. This can only be explained if there is a large polar spot on the primary star extending from the pole to latitude 48 degrees