HS 0943+1404, a true intermediate polar

¹ Department of Physics, University of Warwick, Coventry CV4 7AL, UK e-mail: prguez@iac.es
² Instituto de Astrofísica de Canarias, Vía Láctea, s/n, La Laguna, 38205 Santa Cruz de Tenerife, Spain
³ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁴ Hida Observatory, Kyoto University, Kamitakara, Gifu 506-1314, Japan
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
⁶ Tuorla Observatory, Turku University, Väisäläntie 20, 21500 Piikkiö, Finland
⁷ Department of Physics, 20014 University of Turku, Finland
⁸ School of Physics, University of Exeter, Exeter EX4 4QL, UK
⁹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

Received: 28 March 2005
Accepted: 1 June 2005

Abstract

We have identified a new intermediate polar, HS 0943+1404, as part of our ongoing search for cataclysmic variables in the Hamburg Quasar Survey. The orbital and white dwarf spin periods determined from time-resolved photometry and spectroscopy are min and min, respectively. The combination of a large ratio and a long orbital period is very unusual compared to the other known intermediate polars. The magnetic moment of the white dwarf is estimated to be , which is in the typical range of polars. Our extensive photometry shows that HS 0943+1404 enters into deep (~3 mag) low states, which are also a characteristic feature of polars. We therefore suggest that the system is a true “intermediate” polar that will eventually synchronise, that is, a transitional object between intermediate polars and polars. The optical spectrum of HS 0943+1404 also exhibits a number of unusual emission lines, most noticeably Nλ5680, which is likely to reflect enhanced nitrogen abundances in the envelope of the secondary.