A5060988369- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Electronic Packaging and Soldering Technologies
- Mechanics and Biomechanics Studies
- High-pressure geophysics and materials
- Superconducting Materials and Applications
- Physics of Superconductivity and Magnetism
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Metallurgical and Alloy Processes
- Induction Heating and Inverter Technology
Durham University
2016-2022
The nature and geometry of the hard state in black hole binaries is controversial. broad-band continuum spectrum fast variability properties can be explained a model where inner disc evaporates into geometrically thick, hot flow. However, these models are challenged by persistent detection an extremely broad iron line, which requires that extends down to last stable orbit high-spin hole. This line width considerably reduced if Comptonization multicomponent rather than single temperature, but...
We develop new techniques to deconvolve the radial structure of X-ray emission region in bright low/hard state black hole Cygnus X-1 using both spectral and timing data 3-35~keV range. The spectrum at these energies is dominated by Comptonisation rather than disc, but there a complex pattern time lags between different energy bands differences normalisation shape power spectra bands, which clearly shows that not produced from single, homogeneous region. use physically based model density...
We build a full spectral-timing model for the low/hard state of black hole binaries assuming that spectrum X-ray hot flow can be produced by two Comptonization zones. Slow fluctuations generated at largest radii/softest spectral region propagate down to modulate faster in spectrally harder close hole. The observed and variability are summing over all regions flow, including its emission reflected from truncated disc. This produces energy-dependent Fourier lags qualitatively similar those...
Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like log-normal distribution flux and linear rms-flux relation, which indicate the underlying process is stochastic in nature. It also thought be intrinsic accretion. This has been modelled as inward propagating fluctuations mass accretion rate, although physical driving...
All large superconducting applications require electrical connections between superconductors or and other metallic parts of the systems. Such are essential components for these usually made by melting solder (or soft soldering). In general, point, resistivity, mechanical wetting properties, toxicity all important criteria when choosing best a specific application. If itself is under operating conditions application, then there also possibility extremely low resistance joints. this work, we...
Recent monitoring campaigns designed to map the accretion regime in AGN show major discrepancies with models where optical/ultraviolet (UV) is produced by X-ray-illuminated, optically thick disc material within a few hundred gravitational radii. However, these only monitored X-rays below $10$ keV, whereas bolometric luminosity for most of peaks above $50$ keV. We use data from recent multiwavelength campaign \cite{E17} on NGC 4151 - bright enough be at higher energies \textit{Swift} BAT....
ABSTRACT We explore the accretion geometry in Arakelian 120 using intensive UV and X-ray monitoring from Swift. The hard X-rays (1–10 keV) show large amplitude, fast (few-day) variability, so we expect reverberation disc to produce variability varying illumination. model spectral energy distribution (SED) including an outer standard (optical), intermediate warm-Comptonization region (UV soft X-ray), a hot corona (hard X-rays). Unlike lower Eddington fraction AGN (NGC 4151 NGC 5548 at L/LEdd...