A quasi-periodic modulation of the iron line centroid energy in the black hole binary H1743−322

Abstract

Accreting stellar-mass black holes often show a 'Type-C' quasi-periodic oscillation (QPO) in their X-ray flux, and an iron emission line in their X-ray spectrum. The iron line is generated through continuum photons reflecting off the accretion disk, and its shape is distorted by relativistic motion of the orbiting plasma and the gravitational pull of the black hole. 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 flow to precess as the spinning black hole twists up the surrounding space-time. This predicts a characteristic rocking of the iron line between red and blue shift as the receding and approaching sides of the disk are respectively illuminated. Here we report on XMM-Newton and NuSTAR observations of the black hole binary H 1743-322 in which the line energy varies systematically over the ∼ 4 s QPO cycle (3.70σ significance), as predicted. This provides strong evidence that the QPO is produced by Lense-Thirring precession, constituting the first detection of this effect in the strong gravitation regime. There are however elements of our results harder to explain, with one section of data behaving differently to all the others. Our result enables the future application of tomographic techniques to map the inner regions of black hole accretion disks.

Discovery of a soft X-ray 8 mHz QPO from the accreting millisecond pulsar IGR J00291+5934

“…3), we investigated the dependence of the energy distribution of the source X-ray emission as a function of the QPO phase. We follow the procedure outlined by Ingram & van der Klis (2015) and Ingram et al (2016). A key ingredient in this method is the average phase lag of the source signal at the QPO frequency, compared to a reference band.…”

Modelling the energy dependence of black hole binary flows

“…The correlated QPO can also be produced from the same geometry if the entire hot flow undergoes LenseThirring precession due to its misalignment with the black hole spin axis (Fragile & Meier 2009;Ingram, Done & Fragile 2009;Liska et al 2017). These propagating fluctuation/Lense-Thirring precession models have quantitatively fit the data from XTE J1550−584 during its spectral transition, with the inner radius of the thin disc changing from ∼60 to 12R g (ID11; Ingram & Done 2012a, hereafter ID12a), while also correctly predicting the modulation of the iron line energy on the QPO period (Ingram & Done 2012b;Ingram et al 2016).…”

A tilted and warped inner accretion disc around a spinning black hole: an analytical solution

“…This could be explained assuming the LT precession of a tilted thin accretion disc, which can act as the reflector to give rise to the observed Fe line (e.g., see sections 6.1 and 6.3 of Ingram et al 2017). Therefore, the discovery of Ingram et al (2016) suggests a tilted inner disc.…”

“…Although, Bardeen and Petterson (1975) predicted that the inner accretion disc should be in the equatorial plane with respect to the black hole spin axis, a recent Xray observation has suggested a tilted disc (Ingram et al 2016). Before discussing this, let us provide a brief background on two relevant X-ray features.…”

“…At least some of these timing features are believed to originate from various natural disc oscillations, including the LT precession, from the inner part of the accretion disc (Belloni and Stella (2014) and references therein). Ingram et al (2016) has recently reported that the broad relativistic Fe line energy from the accreting black hole H1743-322 systematically varies with the phase of a QPO. This could be explained assuming the LT precession of a tilted thin accretion disc, which can act as the reflector to give rise to the observed Fe line (e.g., see sections 6.1 and 6.3 of Ingram et al 2017).…”