Home Publications Research Grants Inventions & Patents Awards Additional Research Activities Faculties & Institutions Research Areas

Joint spectral-timing modelling of the hard lags in GX 339-4: constraints on reflection models

Cassatella P, Uttley P, Wilms J, Poutanen J (2012)

---

Publication Status: Published

Publication Type: Journal article

Publication year: 2012

Journal

Publisher: WILEY-BLACKWELL

Book Volume: 422

Pages Range: 2407-2416

Journal Issue: 3

DOI: 10.1111/j.1365-2966.2012.20792.x

Abstract

The X-ray variations of hard state black hole X-ray binaries above 2 keV show hard lags, in that the variations at harder energies follow variations at softer energies, with a time lag t depending on frequency ? approximately as t??-0.7. Several models have so far been proposed to explain this time delay, including fluctuations propagating through an accretion flow, spectral variations during coronal flares, Comptonization in the extended hot corona or a jet, or time delays due to large-scale reflection from the accretion disc. In principle, these models can be used to predict the shape of the energy spectrum as well as the frequency dependence of the time lags, through the construction of energy-dependent response functions which map the emission as a function of time delay in the system. Here we use this approach to test a simple reflection model for the frequency-dependent lags seen in the hard state of GX 339-4, by simultaneously fitting the model to the frequency-dependent lags and energy spectrum measured by XMMNewton in 2004 and 2009. Our model cannot simultaneously fit both the lag and spectral data, since the relatively large lags require an extremely flared disc which subtends a large solid angle to the continuum at large radii, in disagreement with the observed Fe Ka emission. Therefore, we consider it more likely that the lags >2 keV are caused by propagation effects in the accretion flow, possibly related to the accretion disc fluctuations which have been observed previously.

Authors with CRIS profile

Involved external institutions

How to cite

APA:

Cassatella, P., Uttley, P., Wilms, J., & Poutanen, J. (2012). Joint spectral-timing modelling of the hard lags in GX 339-4: constraints on reflection models. Monthly Notices of the Royal Astronomical Society, 422(3), 2407-2416. https://dx.doi.org/10.1111/j.1365-2966.2012.20792.x

MLA:

Cassatella, P., et al. "Joint spectral-timing modelling of the hard lags in GX 339-4: constraints on reflection models." Monthly Notices of the Royal Astronomical Society 422.3 (2012): 2407-2416.

BibTeX: Download