Do observations reveal accretion discs in intermediate polars?

Abstract

It has been proposed that intermediate polars do not accrete through discs and that they may not possess discs. Observations of eclipses and emission lines provide strong evidence that discs are present in many intermediate polars, although it is less clear whether the accretion flows through these discs. An anaysis of the EXOSAT database shows that many systems have orbital and beat period modulations which are small compared to the spin-pulses, suggesting disc accretion. There are, though, exceptions, notably TX Col where dominant orbital and beat period modulations indicate discless accretion.