Multistate observations of the Galactic black hole XTE J1752-223: Evidence for an intermediate black hole spin

Caetano Reis e Sousa, J. M. Miller, A. C. Fabian, Edward M Cackett, D. Maitra, C. S. Reynolds, M. Rupen, D. T H Steeghs, Rudy A D Wijnands

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Abstract

The Galactic black hole candidate XTE J1752-223 was observed during the decay of its 2009 outburst with the Suzaku and XMM-Newton observatories. The observed spectra are consistent with the source being in the 'intermediate' and 'low-hard' states, respectively. The presence of a strong, relativistic iron emission line is clearly detected in both observations and the line profiles are found to be remarkably consistent and robust to a variety of continuum models. This strongly points to the compact object in XTE J1752-223 being a stellar mass black hole accretor and not a neutron star. Physically motivated and self-consistent reflection models for the Fe Kα emission-line profile and disc reflection spectrum rule out either a non-rotating, Schwarzschild black hole or a maximally rotating, Kerr black hole at greater than 3σ level of confidence. Using a fully relativistic line function in which the black hole spin parameter is a variable, we have formally constrained the spin parameter to be 0.52 ± 0.11(1σ). Furthermore, we show that the source in the low-hard state still requires an optically thick disc component having a luminosity which is consistent with the L∝T4 relation expected for a thin disc extending down to the innermost stable circular orbit. Our result is in contrast to the prevailing paradigm that the disc is truncated in the low-hard state.

Original languageEnglish
Pages (from-to)2497-2505
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume410
Issue number4
DOIs
Publication statusPublished - Feb 2011
Externally publishedYes

Keywords

  • Accretion, accretion discs
  • Black hole physics
  • Line: profiles
  • Relativistic processes
  • X-rays: binaries
  • X-rays: individual: XTE J1752-223

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