STJ observations of the eclipsing polar HU Aqr

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 William Herschel Telescope in 2000 October, providing high signal‐to‐noise ratio 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 occurring on to 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.

Temperature determination via STJ optical spectroscopy

“…the orbital plane. We therefore observe more of the heated face of the stream than in HU Aqr or EP Dra where there is evidence for accretion at only one region on the white dwarf (Bridge et al 2002a(Bridge et al , 2002b. Material is still probably heated in HU Aqr at the threading region, as found by Vrielmann & Schwope (2001) and Harrop-Allin (1999) previously, and this also probably occurs in EP Dra.…”

“…ESA has developed two prototype cameras based on an array of STJ devices, and high time-resolution spectrallyresolved observations of rapidly variable sources such as cataclysmic variables and optical pulsars have been reported (Perryman et al 1999, Bridge et al 2002a, Steeghs et al 2002, Bridge et al 2002b). In addition, we have now demonstrated that we can measure quasar redshifts directly with a precision of ∼ 1% (de Bruijne et al 2002).…”

Detection of a planetary system orbiting the eclipsing polar HU Aqr

“…• 0) (e.g. Bridge et al 2002), they should be giant planets. From our best fit, HU Aqr (AB)b is moving around the polar in circular orbit, whereas HU Aqr (AB)c is in an elliptical orbit with eccentricity of 0.51.…”

High-speed, energy-resolved STJ observations of the AM Her system V2301 Oph

“…Technical descriptions of the instrument may be found in Rando et al (1998Rando et al ( , 2000, while the data acquisition and reduction methods are outlined in Perryman et al (1999Perryman et al ( , 2001. In our previous studies of CVs (Perryman et al 2001;Bridge et al 2002Bridge et al , 2003Steeghs et al 2003) our main tool for Table 1. Observations of V2301 Oph obtained using S-Cam2.…”