Open AccessHT Camelopardalis: the simplest intermediate polar spin pulse
Author(s) -
Evans P. A.,
Hellier Coel
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09001.x
Subject(s) - physics , opacity , astrophysics , intermediate polar , accretion (finance) , polar , polar cap , absorption (acoustics) , cataclysmic variable star , accretion disc , pulse (music) , occultation , light curve , astronomy , white dwarf , stars , optics , detector
The intermediate polar (IP) 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.