A PHOTOMETRIC AND SPECTROSCOPIC STUDY OF BG CANIS-MINORIS

The photometric and spectroscopic analysis presented here has revealed new observational features in the Intermediate Polar BG CMi. We have found a strong variability of the dominant light pulsations, rotationa l (913 s) and orbital (3.23 hr), on a timescale of years. Variations i n the amplitude of the spin pulsation with epoch generally appear to b e anti-correlated with that of the orbital modulation with the former decreasing while the latter increases. We do not find stable periodic signals at other frequencies as well as no indication of periodicity a t the 847 s X-ray period. UV and optical orbital continuum modulations reveal two components at different temperatures. The hot contribution is identified with the bulge (the heated face of the hot-spot) and th e cool one with the hot-spot itself eclipsed by the secondary star. Or bital phase resolved spectroscopy reveals a rotational disturbance in the HeII emission line, indicating a partial eclipse of circulating ma terial around the white dwarf, possibly in the form of a ring. From th e orbital motion of the white dwarf, we also infer that BG CMi is a mo derate inclination system (i similar to 55 degrees - 75 degrees).