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Astron. Astrophys. 319, 894-908 (1997)

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Phase-resolved high-resolution spectrophotometry of the eclipsing polar HU Aquarii

Axel D. Schwope * 1, Karl-Heinz Mantel * 2 and Keith Horne 3

1 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany (ASchwope@aip.de)
2 Universitätssternwarte München, Scheinerstrasse 1, D-81679 München, Germany
3 Univ. of St. Andrews, School of Physics and Astronomy, North Haugh, St. Andrews, Fife KY16 9SS, Scotland, UK

Received 29 April 1996 / Accepted 27 August 1996


We present phase-resolved spectroscopy of the bright, eclipsing polar HU Aqr obtained with high time ([FORMULA] 30 sec) and spectral (1.6Å) resolution when the system was in a high accretion state. The trailed spectrograms reveal clearly the presence of three different line components with different width and radial velocity variation. By means of Doppler tomography their origin could be located unequivocally (a) on the secondary star, (b) the ballistic part of the accretion stream (horizontal stream), and (c) the magnetically funnelled part of the stream (vertical stream). For the first time we were able to derive a (near-)complete map of the stream in a polar. We propose to use Doppler tomography of AM Herculis stars as a new tool for the mass determination of these binaries. This method, however, still needs to be calibrated by an independent method. The asymmetric light curve of the narrow emission line originating on the mass-donating companion star reveals evidence for significant shielding of 60% of the leading hemisphere by the gas between the two stars.

Key words: accretion – cataclysmic variables – stars: HU Aqr (= RX J2107.9 – 0518) – binaries: eclipsing

* Visiting astronomer, German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy.

Send offprint requests to: Axel D. Schwope

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998