Polarimetry, photometry and spectroscopy of the intermediate polar V1223 Sgr.

We report optical and IR polarization studies of the intermediate polar V1223 Sgr. The optical and IR light curves have assisted in the determination by Warner & Cropper of the photometric period of 0.14 day. The IR flux of the 794-s pulsations is consistent with X-ray heating of a cool atmosphere. The white-dwarf spin period of 746s was not detected and upper limits to pulsed polarization at this period are ±3 per cent at V, ±0.5 per cent at R, +0.5/-1.O per cent at J and ±8 per cent at K. The IR data are consistent with the published fit of a steady state optically thick disc model to the optical and UV continua. No IR excess from the secondary is apparent. High-dispersion spectroscopic observations over half the orbital period show a small radial velocity change accompanied by complex line profile changes. The low mass function of 0.0026±0.0015 M_sun implies a low inclination (<40° ) for a main-sequence companion. The line profile changes are consistent with an S-wave behaviour and place the hotspot on the centres-of-mass line.