T. Wilkinson | Searcharxiv

arXiv2017

Theory Plug-in for Rodin 3.x

The Theory plug-in enables modellers to extend the mathematical modelling notation for Event-B, with accompanying support for reasoning about the extended language. Previous version of the Theory plug-in has been implemented based on Rodin 2.x. This presentation outline the main improvements to the The- ory plug-in, to be compatible with Rodin 3.x, in terms of both reliability and us- ability. We will also present the changes that were needed in the Rodin core to accommodate the Theory plug-in. Finally, we identify future enhancements and research directions for the Theory plug-in.

cs.SE↗

arXiv2011

The causal connection between disc and power-law variability in hard state black hole X-ray binaries

We use the XMM-Newton EPIC-pn instrument in timing mode to extend spectral time-lag studies of hard state black hole X-ray binaries into the soft X-ray band. We show that variations of the disc blackbody emission substantially lead variations in the power-law emission, by tenths of a second on variability time-scales of seconds or longer. The large lags cannot be explained by Compton scattering but are consistent with time-delays due to viscous propagation of mass accretion fluctuations in the disc. However, on time-scales less than a second the disc lags the power-law variations by a few ms, consistent with the disc variations being dominated by X-ray heating by the power-law, with the short lag corresponding to the light-travel time between the power-law emitting region and the disc. Our results indicate that instabilities in the accretion disc are responsible for continuum variability on time-scales of seconds or longer and probably also on shorter time-scales.

astro-ph.HE↗