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Issue A&A Volume 437, Number 2, July II 2005 Page(s) 637 - 639 Section Stellar structure and evolution DOI 10.1051/0004-6361:20052780

A&A 437, 637-639 (2005)
DOI: 10.1051/0004-6361:20052780

The K-band spectrum of the cataclysmic variable RXJ 0502.8+1624 (Tau 4)

S. P. Littlefair¹, V. S. Dhillon¹ and E. L. Martín<sup>2, 3

1</sup>  Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
    e-mail: S.Littlefair@sheffield.ac.uk
²  Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
³  University of Central Florida, Department of Physics, PO Box 162385, Orlando, FL 32816-2385, USA

(Received 28 January 2005 / Accepted 24 March 2005 )

Abstract
We present the K-band spectrum of the cataclysmic variable RXJ 0502.8+1624 (Tau 4). The spectrum shows a broad, smooth hump, with no absorption lines from the secondary star visible. This result indicates that the infrared light of this system is dominated by cyclotron emission, and, in combination with the optical spectrum and X-ray properties, suggests that Tau 4 is a polar-type cataclysmic variable (CV).

The system was chosen for study because the broadband JHK colours of Tau 4 are consistent with an L-type dwarf, suggesting that this system might harbour an elusive sub-stellar secondary star. The result presented here, along with the recent discovery of cyclotron emission in the cataclysmic variable EF Eri, suggests that care must be taken when using the broadband JHK colours of CVs when targeting searches for sub-stellar secondary stars.

Key words: binaries: spectroscopic -- stars: individual: Tau 4 -- novae, cataclysmic variables -- infrared: stars -- stars: low-mass, brown dwarfs

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© ESO 2005

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