Intermediate polar spin pulse profiles.
AIP Conference Proceedings, 599(1) pp. 806–809.
The X-ray spin pulse profiles of fast rotating intermediate polars (P[sub spin] < 700 s) are double peaked, whilst those of slower rotating systems are not. We believe this is due to the lower magnetic field strength in the short spin period systems, so the radius at which material is captured by the field lines is relatively small. Consequently the footprints of the disc-fed accretion curtains on the white dwarf surface are large. The optical depths to X-ray emission within the accretion curtains are such that the emission from the two poles conspires to produce doublepeaked X-ray pulse profiles. We emphasise, however, that a double-peaked pulse profile is not a unique indicator of two-pole accretion. Indeed, two-pole accretion onto smaller regions of the white dwarf surface may be considered the 'normal' mode of behaviour in a disc-fed intermediate polar with a longer white dwarf spin period, resulting in a single-peaked pulse profile.
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