2007MNRAS.378..635S

Intermediate polars (IPs) are cataclysmic variables which contain magnetic white dwarfs with a rotational period shorter than the binary orbital period. Evolutionary theory predicts that IPs with long orbital periods evolve through the 2-3h period gap, but it is very uncertain what the properties of the resulting objects are. Whilst a relatively large number of long-period IPs are known, very few of these have short orbital periods. We present phase-resolved spectroscopy and photometry of SDSSJ233325.92+152222.1 (SDSSJ2333) and classify it as the IP with the shortest-known orbital period (83.12±0.09min), which contains a white dwarf with a relatively long spin period (41.66±0.13min). We estimate the white dwarf's magnetic moment to be µ_WD~ 2 x 10³³ G.cm3, which is not only similar to three of the other four confirmed short-period IPs but also to those of many of the long-period IPs. We suggest that long-period IPs conserve their magnetic moment as they evolve towards shorter orbital periods. Therefore, the dominant population of long-period IPs, which have white dwarf spin periods roughly 10 times shorter than their orbital periods, will likely end up as short-period IPs like SDSSJ2333, with spin periods a large fraction of their orbital periods.