Modelling correlated variability in accreting black holes: The effect of high density and variable ionization on reverberation lags
Mastroserio G, Ingram A, Wang J, García JA, Van Der Klis M, Cavecchi Y, Connors R, Dauser T, Harrison F, Kara E, König O, Lucchini M (2021)
Publication Type: Journal article
Publication year: 2021
Journal
Book Volume: 507
Pages Range: 55-73
Journal Issue: 1
Abstract
We present a new release of the reltrans model to fit the complex cross-spectrum of accreting black holes as a function of energy. The model accounts for continuum lags and reverberation lags self-consistently in order to consider the widest possible range of X-ray variability time-scales. We introduce a more self-consistent treatment of the reverberation lags, accounting for how the time variations of the illuminating flux change the ionization level of the accretion disc. This process varies the shape of the reflection spectrum in time causing an additional source of lags besides the light crossing delay. We also consider electron densities in the accretion disc up to 1020 cm-3, which are found in most of the stellar mass black holes and in some active galactic nuclei. These high densities increase the amplitude of the reverberation lags below 1 keV since the reflection flux enhances in the same energy range. In addition, we investigate the properties of hard lags produced by variations in the power-law index of the continuum spectrum, which can be interpreted as due to roughly 3 per cent variability in the corona's optical depth and temperature. As a test case, we simultaneously fit the lag-energy spectra in a wide range of Fourier frequency for the black hole candidate MAXI J1820+0701820 observed with NICER. The best fit shows how the reverberation lags contribute even at the longer time-scales where the hard lags are important. This proves the importance of modelling these two lags together and self-consistently in order to constrain the parameters of the system.
Authors with CRIS profile
Thomas Dauser
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Ole König
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Involved external institutions
California Institute of Technology (Caltech)
United States (USA) (US)
University of Oxford
United Kingdom (GB)
Massachusetts Institute of Technology (MIT)
United States (USA) (US)
University of Amsterdam
Netherlands (NL)
National Autonomous University of Mexico / Universidad Nacional Autónoma de México (UNAM)
Mexico (MX)
United States (USA) (US)
University of Oxford
United Kingdom (GB)
Massachusetts Institute of Technology (MIT)
United States (USA) (US)
University of Amsterdam
Netherlands (NL)
National Autonomous University of Mexico / Universidad Nacional Autónoma de México (UNAM)
Mexico (MX)
How to cite
APA:
Mastroserio, G., Ingram, A., Wang, J., García, J.A., Van Der Klis, M., Cavecchi, Y.,... Lucchini, M. (2021). Modelling correlated variability in accreting black holes: The effect of high density and variable ionization on reverberation lags. Monthly Notices of the Royal Astronomical Society, 507(1), 55-73. https://doi.org/10.1093/mnras/stab2056
MLA:
Mastroserio, Guglielmo, et al. "Modelling correlated variability in accreting black holes: The effect of high density and variable ionization on reverberation lags." Monthly Notices of the Royal Astronomical Society 507.1 (2021): 55-73.
BibTeX: Download