XMM-Newton confirmation of the Intermediate Polar HT Cam

Abstract : The X-ray source RX J0757+63 = HT Cam was proposed to be an Intermediate Polar (IP) from its 515 s photometric period (Tovmassian et al. 1998; Kemp et al. 2002). With a 86 min orbital period it was candidate as the third IP below the period gap. We report on the first X-ray XMM-Newton observation. The strong 514.6±0.2 s X-ray modulation definitively confirms HT Cam as an IP and that the X-ray period is the spin period of the accreting white dwarf (WD). HT Cam has a multi-temperature spectrum and, contrary to most IPs, it does not suffer from strong absorption.