A quasi-periodic modulation of the iron line centroid energy in the black hole binary H1743−322
Adam Ingram1,★, Michiel van der Klis1, Matthew Middleton2, Chris Done3, Diego Altamirano4, Lucy Heil1, Phil Uttley1 and Magnus Axelsson5
1Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam, the Netherlands
2Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA, UK
3Center for Extragalactic Astronomy, Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK
4Department of Physics & Astronomy, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
5Department of Physics, Tokyo Metropolitan University, Minami Osawa 1-1, Hachioji, Tokyo 192-0397, Japan
Accepted 2016 May 19. Received 2016 May 19. In original form 2016 April 15. First published online May 25, 2016.
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 disc, 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 blueshift as the receding and approaching sides of the disc are respectively illuminated. Here we report on XMM–Newton andNuSTAR observations of the black hole binary H1743−322 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 than all the others. Our result enables the future application of tomographic techniques to map the inner regions of black hole accretion discs.
Key words accretion, accretion discs black hole physics relativistic processes X-rays: individual: H1743−322
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
FREE PDF GRATIS: MNRAS