Polarimetry of ST LMi (CW1103 + 254)

White-light simultaneous photometry and linear and circular polarimetry is presented for the AM Her type variable STLMi. Linear polarization evident throughout the faint phase is tentatively attributed to electron scattering from gas in the accretion column at heights greater than 5 $$R_{\text {wd}}$$ above the surface. The values of inclination and magnetic dipole offset are revised to take into account the height and extent of the cyclotron emission regions which are also determined. A model of two closely connected emitting regions is proposed to account for the asymmetries observed in the light curve and polarization data for this and other AM Her systems. The size of the soft X-ray pole cap is calculated. The cyclotron and hard X-ray emitting regions are found to be coincident, eliminating the region above the shock as the source of polarized light. Various parameters such as masses, accretion rates and luminosities are calculated for the system. The shock height is found to be too low and the soft X-ray flux too large for the standard radiative-shock model to be applicable.