We present high time-resolution multicolour observations of the quiescent soft Xray transient V404Cyg obtained with ULTRACAM . Superimposed on the secondary star’s ellipsoidal modulation are large flares on timescales of a few hours, as well as several distinct rapid flares on timescales of tens of mins. The rapid flares, most of which show further variability and unresolved peaks, cover shorte...

The large digital frame camera UltraCamX was introduced in 2006 by Vexcel Imaging (a Microsoft Company). This paper will give a short technical overview about the concept of the camera and more information on the radiometric quality of the UltraCamX. The focus in this paper is set on the radiometric quality of the sensors. Already recorded image data are analyzed in detail for their radiometric...

We have measured the X-ray/optical cross-correlation functions (CCFs) of the two black hole binary systems SWIFT J1753.5−0127 and GX 339−4 using ULTRACAM and RXTE. We find each one is unique and different from the one such measurement in the literature, for XTE J1118+480. Our CCFs are inconsistent with reprocessing, and suggest a mechanism which regulates emission between the different spectral...

We present ULTRACAM photometry of ES Cet, an ultracompact binary with a 620-s orbital period. The mass transfer in systems such as this one is thought to be driven by gravitational radiation, which causes the binary to evolve to longer periods since the semidegenerate donor star expands in size as it loses mass. We supplement these ULTRACAM+William Herschel Telescope (WHT) data with observation...