Discovery of polarized emission from the long period intermediate polar RX J2133.7+5107^*

¹ Tuorla Observatory, University of Turku, Väisäläntie 20 21500, Piikkiö, Finland e-mail: [sekataja;hlehto;piirola]@utu.fi
² Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK e-mail: [o.w.butters;A.J.Norton]@open.ac.uk
³ Department of Physics, 20014 University of Turku, Finland
⁴ Vatican Observatory, 00120 Cittá del Vaticano

Received: 6 April 2007
Accepted: 18 September 2007

Abstract

Aims.We intended to investigate the magnetic field properties of the recently identified intermediate polar RX J2133.7+5107.

Methods.We carried out UBVRI photopolarimetric observations of the target using TURPOL on the Nordic Optical Telescope over 2 nights in July/August 2006.

Results.We found that RX J2133.7+5107 emits circularly polarized light in all UBVRI bands (up to ). This is the first detection of circular polarization in this object. The circular polarization modulations and flux variations give hints of cyclotron beaming effects and suggest that the field strength in RX J2133.7+5107 is possibly one of the highest found amongst the IPs.

Conclusions.The highly asynchronous rotation of RX J2133.7+5107 (the spin to orbital period ratio is ∼0.022), suggests that it has only recently come into contact and although it is likely to evolve into a polar, it is currently a long way from doing so. We suggest a possible link between the detection of a soft X-ray blackbody component and polarized optical emission in intermediate polars.