The spin period of the intermediate polar RX J0558+53.

The newly discovered intermediate polar RX J0558.0+5353 has been reported to have a spin period of 272 s. The authors find modulations at both 272 and 545 s, implying that the spin period of the white dwarf is twice that previously suggested. Thus, RX J0558.0+5353, along with YY Dra, is unusual in showing a modulation with most of the power at the first harmonic, rather than at the spin frequency.