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SDSS J233325.92+152222.1 and the evolution of intermediate polars
Authors:John Southworth  B T Gänsicke  T R Marsh  D de Martino  A Aungwerojwit
Institution:Department of Physics, University of Warwick, Coventry CV4 7AL;INAF –Osservatorio di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy;Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 60500, Thailand
Abstract: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 2–3 h 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 SDSS J233325.92+152222.1 (SDSS J2333) and classify it as the IP with the shortest-known orbital period (83.12 ± 0.09 min), which contains a white dwarf with a relatively long spin period (41.66 ± 0.13 min). We estimate the white dwarf's magnetic moment to be μWD≈ 2 × 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 SDSS J2333, with spin periods a large fraction of their orbital periods.
Keywords:binaries: close  stars: individual: SDSS J233325  92+152222  1  stars: magnetic fields  novae  cataclysmic variables  white dwarfs
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