English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Accreting black hole sources show a wide variety of rapid time variability,including the manifestation of time lags during X-ray transients, in which adelay (phase shift) is observed between the Fourier components of the hard andsoft spectra. Despite a large body of observational evidence for time lags, nofundamental physical explanation for the origin of this phenomenon has beenpresented. We develop a new theoretical model for the production of X-ray timelags based on an exact analytical solution for the Fourier transform describingthe diffusion and Comptonization of seed photons propagating through aspherical corona. The resulting Green's function can be convolved with anysource distribution to compute the associated Fourier transform and time lags,hence allowing us to explore a wide variety of injection scenarios. We showthat thermal Comptonization is able to self-consistently explain both the X-raytime lags and the steady-state (quiescent) X-ray spectrum observed in thelow-hard state of Cyg X-1. The reprocessing of bremsstrahlung seed photonsproduces X-ray time lags that diminish with increasing Fourier frequency, inagreement with the observations for a wide range of sources.

A Fourier Transformed Bremsstrahlung Flash Model for the Production of X-Ray Time Lags in Accreting Black Hole Sources