The nature of TW Pictoris

The results of X-ray and optical observations of the candidate intermediate polar TW Pic are presented in an attempt to understand its nature. We find no sign of the previously proposed similar to 2 h white-dwarf spin period and similar to 6 h orbital period of TW Pic in its X-ray light curve. There is therefore no convincing evidence in support of its previous classificat ion. The lack of X-ray pulsation could be the result of a low inclination a ngle, but in that case there would be no reason why an optical pulsation sh ould have been seen previously. Negative results from polarimetry also prec lude TW Pic from being a polar. One possibility may be that the shorter of the two periods is in fact the orbital period, whilst the longer one is a h armonic of a disc precession period. Alternatively, both the high accretion rate and period structure of TW Pic indicate that it may be a system that displays persistent negative superhumps. In this case the true orbital peri od of the binary may be around 6.36 h and the shorter of the two previously identified periods, 1.996 h, represents the (shifted) second harmonic of a negative superhump period of 6.06 h. Under this interpretation, it would b e the longest period system to display such a phenomenon. Finally then is a lso evidence that TW Pic may be a VY Scl star, in which case it would be th e longest period member of that subclass too.