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.

We present the first high time resolution light curves for six eclipses of the magnetic cataclysmic variable EP Dra, taken using the superconducting tunnel junction imager S-Cam2. The system shows a varying eclipse profile between consecutive eclipses over the two nights of observation. We attribute the variable stream eclipse after accretion region ingress to a variation in the amount and location of bright material in the accretion stream. This material creates an accretion curtain as it is threaded by many field lines along the accretion stream trajectory. We identify this as the cause of absorption evident in the light curves when the system is in a high accretion state. We do not see direct evidence in the light curves for an accretion spot on the white dwarf; however, the variation of the stream brightness with the brightness of the rapid decline in flux at eclipse ingress indicates the presence of some form of accretion region. This accretion region is most likely located at high colatitude on the white dwarf surface, forming an arc shape at the foot points of the many field lines channelling the accretion curtain.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA riser fatigue monitoring strategy and implementation on a deepwater Gulf of Mexico Spar top tensioned riser is presented. The paper explains why a fatigue monitoring program is considered necessary to provide the operator with assurance of the riser system performance and integrity in service, the considerations that led to the selection of an appropriate monitoring system and describes in detail the standalone motion logger system adopted.The principles and methods of measurements that permit the monitoring of motions at discrete locations on the riser are presented along with the methods of processing this data such that fatigue damage along the riser can be interpreted.The paper describes how a standalone logger monitoring system has been successfully installed entirely using a ROV, eliminating the need to run the monitoring system during critical path riser installation activities.

Abstract. We present high time-resolution optical energy-resolved photometry of the eclipsing cataclysmic variable V2301 Oph made using the ESA S-Cam detector, an array of photon counting super-conducting tunnel junction (STJ) devices with intrinsic energy resolution. Three eclipses were observed, revealing considerable variation in the eclipse shape, particularly during ingress. The eclipse shape is shown to be understood in terms of AM Her accretion via a bright stream, with very little contribution from the white dwarf photosphere and/or hotspot. About two thirds of the eclipsed light arises in the threading region. Variation in the extent of the threading region can account for most of the variations observed between cycles. Spectral fits to the data reveal a 10 000 K blackbody continuum with strong, time-varying emission lines of hydrogen and helium. This is the first time that stellar emission lines have been detected in the optical band using a non-dispersive photon-counting system.

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