Dense spot coverage and polar caps on SV Cam

Abstract

We have used spectrophotometric data from nine Hubble Space Telescope orbits to eclipse-map the primary component of the RS CVn binary SV Cam. From these observations and its HIPPARCOS parallax we find that the surface flux in the eclipsed low-latitude region is about 30% lower than computed from the best fitting PHOENIX model atmosphere. This flux deficit can only be accounted for if about a third of the primary's surface is covered with unresolved spots. Even when we extend the spottedness from the eclipsed region to the entire surface, there still remains an unaccounted flux deficit. This remaining flux deficit is explained by the presence of a large polar spot extending down to latitude 42 +/- 6 degrees..