Discovery of circular polarization in the Intermediate Polar 1WGA J1958.2+3232

We report on UBVRI polarimetry of the recently identified Intermediate Polar 1WGA J1958.2+3232, carried out on 2000 August, 4-6 at the Nordic Optical Telescope. Circular polarization was detected in R and I bands with an increasing absolute mean value with wavelength. There is evidence of possible modulation of the circular polarization at twice the previously reported white dwarf spin period, suggesting that it is the true period and that the modulation in optical and X-ray is dominated by the first harmonic. Indication of modulation at the orbital period is also present. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.