HT Camelopardalis: The simplest intermediate polar spin pulse

Abstract

The intermediate polar HT Cam is unusual in that it shows no evidence for dense absorption in its spectrum. We analyse an XMM-Newton observation of this star, which confirms the absence of absorption and shows that the X-ray spin-pulse is energy independent. The modulation arises solely from occultation effects and can be reproduced by a simple geometrical model in which the lower accretion footprint is fainter than the upper one. We suggest that the lack of opacity in the accretion columns of HT Cam, and also of EX Hya and V1025 Cen, results from a low accretion rate owing to their being below the cataclysmic variable period gap.

5 pages, 6 figures, accepted for publication in MNRAS

References in corpus (5)

• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• Two Types of X-ray Spectra in Cataclysmic Variables
• BeppoSAX observations of soft X-ray Intermediate Polars
• Why does the intermediate polar V405 Aurigae show a double-peaked spin pulse?
• Rapid Oscillations in Cataclysmic Variables. XV. HT Camelopardalis (= RX J0757.0+6306)

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• CC Sculptoris: Eclipsing SU UMa-Type Intermediate Polar
• Disc-Magnetosphere interactions in Cataclysmic Variable Stars
• Significant reflection and absorption effects in the X-ray emission of the Intermediate Polar IGR J17195-4100