STJ observations of the eclipsing polar HU Aqr

Authors :: Gavin Ramsay
Nicola Rando
J. H. J. de Bruijne
Fabio Favata
Anthony J. Peacock
Michael Perryman
C. M. Bridge
Mark Cropper
A. P. Reynolds
Source :: Monthly Notices of the Royal Astronomical Society. 336:1129-1138
Publication Year :: 2002
Publisher :: Oxford University Press (OUP), 2002.
Abstract: We apply an eclipse mapping technique to observations of the eclipsing magnetic cataclysmic variable HU Aqr. The observations were made with the S-Cam2 Superconducting Tunnel Junction detector at the WHT in October 2000, providing high signal-to-noise observations with simultaneous spectral and temporal resolution. HU Aqr was in a bright (high accretion) state (V=14.7) and the stream contributes as much to the overall system brightness as the accretion region on the white dwarf. The stream is modelled assuming accretion is occuring onto only one pole of the white dwarf. We find enhanced brightness towards the accretion region from irradiation and interpret enhanced brightness in the threading region, where the ballistic stream is redirected to follow the magnetic field lines of the white dwarf, as magnetic heating from the stream-field interaction, which is consistent with recent theoretical results. Changes in the stream eclipse profile over one orbital period indicate that the magnetic heating process is unstable.<br />Comment: Accepted for publication in MNRAS (11 pages)