Open AccessSimultaneous optical polarimetry and X‐ray observations of the magnetic CV CP Tuc (AX J2315−592)
Author(s) -
Ramsay Gavin,
Potter S. B.,
Buckley David A. H.,
Wheatley Peter J.
Publication year - 1999
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 - 10.1046/j.1365-8711.1999.02569.x
Subject(s) - physics , astrophysics , white dwarf , polar , polarimetry , accretion (finance) , intermediate polar , polarization (electrochemistry) , astronomy , eclipse , magnetic dip , stars , scattering , optics , chemistry
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 were 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 polarization 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 polarization data implies 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.