Tomographic mapping of accreting black holes using X-ray quasi-periodic oscillations
Abstract
Accreting stellar-mass black holes often show a quasi-periodic oscillation (QPO) in their X-ray flux with a period that slowly drifts from 10s to 0.05s. The physical origin of the QPO has long been debated, but is often attributed to Lense-Thirring precession, a General Relativistic effect causing the inner accretion flow to precess as the spinning black hole twists up the surrounding space-time. A distinctive prediction of the precession model is that the iron fluorescence line, produced as part of a `reflection' spectrum by disk irradiation, should rock between red- and blue-shifted as the receding and approaching sides of the disk are respectively illuminated by the precessing inner accretion flow. Our recent XMM-Newton and NuSTAR observations in which the centroid energy of the iron line in H 1743-322 varies systematically over the _4 s QPO cycle, confirm this prediction and thus provide strong evidence in favour of the precession model. Here I will focus on the tomographic mapping techniques that this result has enabled. This entails developing a physical model for the QPO phase-dependent reflection spectrum and fitting to the observed QPO phase-resolved spectra. I will present results for our campaign on H 1743-322 and also for NICER observations of the recently discovered source, MAXI J1535-571. I will present results of modelling that additionally takes into account thermal reprocessing, which exploits the very high count rates achieved by NICER in the soft X-ray band.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1551I