Free access article

A&A 384, 195-205 (2002)
DOI: 10.1051/0004-6361:20011820

Pulsations and orbital modulation of the intermediate polar 1WGA J1958.2+3232

A. J. Norton¹, H. Quaintrell¹, S. Katajainen², H. J. Lehto², K. Mukai³ and I. Negueruela<sup>4

1</sup>  Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
    e-mail: A.J.Norton@open.ac.uk; H.Quaintrell@open.ac.uk
²  Tuorla Observatory, Turku University, Väisäläntie 20, 21500 Piikkiö, Finland
    e-mail: sekataja@astro.utu.fi; hlehto@astro.utu.fi
³  NASA Goddard Space Flight Center, Laboratory for High Energy Astrophysics, Code 662, Greenbelt, MD 20771, USA and Universities Space Research Association
    e-mail: mukai@milkyway.gsfc.nasa.gov
⁴  Observatoire Astronomique de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
    e-mail: ignacio@isaac.u-strasbg.fr

(Received 20 November 2001 / Accepted 20 December 2001 )

Abstract
We present optical photometry, spectroscopy and photopolarimetry, as well as ASCA X-ray observations, of the recently discovered intermediate polar 1WGA J1958.2+3232. Through the first detection of an optical beat frequency, we confirm the previously tentative suggestion that the spin period of the white dwarf is twice the X-ray and optical pulsation period, which we also confirm in each case. We detect an orbital modulation in each of the U, B, V, R and I bands for the first time, and suggest that the true orbital period is the -1d alias of that previously suggested. We also confirm the presence of circular polarization in this system, detecting a variable polarization which has opposite signs in each of the B and R bands. The double peaked pulse profile and oppositely signed polarization pulses suggest that 1WGA J1958.2+3232 accretes onto both magnetic poles via a disc which is truncated relatively close to the white dwarf.

Key words: novae, cataclysmic variables -- stars: magnetic fields -- stars: individual -- 1WGA J1958.2+3232

Offprint request: A. J. Norton, A.J.Norton@open.ac.uk

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