EDP Sciences
Free access
Volume 440, Number 2, September III 2005
Page(s) 701 - 709
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20053141

A&A 440, 701-709 (2005)
DOI: 10.1051/0004-6361:20053141

HS 0943+1404 , a true intermediate polar

P. Rodríguez-Gil1, 2, B. T. Gänsicke1, H.-J. Hagen3, D. Nogami4, M. A. P. Torres5, H. Lehto6, 7, A. Aungwerojwit1, S. Littlefair8, S. Araujo-Betancor9 and D. Engels3

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 )

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 $P_\mathrm{orb} \simeq 250$ min and $\mbox{$P_\mathrm{spin}$ }= 69.171 \pm 0.001$ min, respectively. The combination of a large ratio $\mbox{$P_\mathrm{spin}$ }/\mbox{$P_\mathrm{orb}$ }\simeq0.3$ 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 $\mu_1\sim10^{34}\,\mathrm{G\,cm^{3}}$, 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 N$\rm _{II}$$\lambda$5680, which is likely to reflect enhanced nitrogen abundances in the envelope of the secondary.

Key words: accretion, accretion disc -- stars: binaries: close -- stars: novae, cataclysmic variables

SIMBAD Objects

© ESO 2005