Simultaneous optical polarimetry and X-ray observations of the magnetic CV CP Tuc (AX J2315--592)

Gavin Ramsay; Stephen Potter; David Buckley; Peter Wheatley

doi:10.1046/j.1365-8711.1999.02569.x

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arXiv · astro-ph/9902324

Simultaneous optical polarimetry and X-ray observations of the magnetic CV CP Tuc (AX J2315--592)

Gavin Ramsay·Stephen Potter·David Buckley·Peter Wheatley

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Abstract

CP Tuc (AX J2315--592) shows a dip in X-rays which lasts for approximately half the binary orbit and is deeper in soft X-rays compared with hard X-rays. It has been proposed that this dip is due to the accretion stream obscuring the accretion region from view. If CP Tuc was a polar, as has been suggested, then the length of such a dip would make it unique amongst polars since in those polars in which a dip is seen in hard X-rays the dip lasts for only 0.1 of the orbit. We present optical polarimetry and RXTE observations of CP Tuc which show circular polarisation levels of ~10 per cent and find evidence for only one photometric period. These data confirm CP Tuc as a polar. Our modelling of the polarisation data imply that the X-ray dip is due to the bulk of the primary accretion region being self-eclipsed by the white dwarf. The energy dependence of the dip is due to a combination of this self-eclipse and also the presence of an X-ray temperature gradient over the primary accretion region.

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Gavin Ramsay, Stephen Potter, David Buckley, Peter Wheatley. 1999-02-23. Simultaneous optical polarimetry and X-ray observations of the magnetic CV CP Tuc (AX J2315--592). https://doi.org/10.1046/j.1365-8711.1999.02569.x

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