VKOMPTH: a spectral-timing model for Comptonisation

FEDERICO GARCÍA

Atenas

Conferencia; COSPAR ASSEMBLY 2022; 2022

COSPAR Commitee on Space Research

Given the strength of the X-ray variability associated to X-ray binaries, the modelling of the spectral-timing properties of these sources has become essential to study the physical and geometrical properties of accretion flows in these systems. The power density spectra of these sources offently present narrow components, the so-called quasi-periodic oscillations (QPOs) which encode not only dynamical, but also radiative properties of these sources. In particular, it has been shown that the fractional variability amplitude of these QPOs tends to increase with energy, reaching variabilities of 10-20\% at 10-100 keV, where emission due to inverse-Compton scattering dominates the spectrum. In this talk, I will present the VKOMPTH model developed by our group, which simultaneously fits the energy-dependent complex-variability spectra, encoded in the fractional rms and phase lags of these QPOs, together with the time-averaged or steady spectrum of the source, by considering oscillations in the properties of the corona attached to the source of soft-photons for Comptonisation. We have already applied VKOMPTH to both high-frequency kHz QPOs in neutron star systems and low-frequency Hz QPOs in black hole binaries. During this talk, I will also summarize the main results obtained with this model.