Multi-wavelength spectrophotometry of EX Hydrae

Free access article

Issue		A&A Volume 382, Number 3, February II 2002


Page(s)		984 - 998
Section		Formation, structure and evolution of stars
DOI		http://dx.doi.org/10.1051/0004-6361:20011655

A&A 382, 984-998 (2002)
DOI: 10.1051/0004-6361:20011655

Multi-wavelength spectrophotometry of EX Hydrae

S. Eisenbart, K. Beuermann, K. Reinsch and B. T. Gänsicke

Universitäts-Sternwarte, Geismarlandstr. 11, 37083 Göttingen, Germany

(Received 1 October 2001 / Accepted 16 November 2001)

Abstract
We present phase-resolved infrared and optical spectrophotometry of the intermediate polar EX Hya supplemented by archival ultraviolet data. The spin-modulated emission from the accretion funnel and the emission from the accretion disk or ring contain substantial optically thin components. The white dwarf dominates the unmodulated flux in the ultraviolet and is identified by numerous absorption lines. Metal absorption in the accretion curtain may add to the observed spectral features. The secondary star is of spectral type M4 $\pm~1$ and is detected by its ellipsoidal modulation. We derive a distance of $65\pm11\,$ pc which makes EX Hydrae one of the closest cataclysmic variables with a known distance. The luminosity derived from the integrated overall spectral energy distribution is ${3}\times 10^{32}\,$ erg s ^-1. The accretion rate of ${3}\times 10^{15}\,$ g s ^-1 (for an 0.6 $M_{\odot}$ white dwarf) is in reasonable agreement with the rates expected from angular momentum loss by gravitational radiation and from the observed spin-up of the white dwarf.

Key words: stars: individual: EX Hydrae -- cataclysmic variables -- accretion

Offprint request: K. Beuermann, beuermann@uni-sw.gwdg.de

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