Journal Article

The spin of the black hole microquasar XTE J1550−564 via the continuum-fitting and Fe-line methods

James F. Steiner, Rubens C. Reis, Jeffrey E. McClintock, Ramesh Narayan, Ronald A. Remillard, Jerome A. Orosz, Lijun Gou, Andrew C. Fabian and Manuel A. P. Torres

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 2, pages 941-958
Published in print September 2011 | ISSN: 0035-8711
Published online September 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19089.x
The spin of the black hole microquasar XTE J1550−564 via the continuum-fitting and Fe-line methods

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We measure the spin of XTE J1550−564 using the two leading methods: (i) modelling the thermal continuum spectrum of the accretion disc; and (ii) modelling the broad red wing of the reflection fluorescence Fe Kα line. We find that these two independent measurements of spin are in agreement. For the continuum-fitting analysis, we use a data sample consisting of several dozen Rossi X-ray Timing Explorer spectra, and for the Fe Kα analysis, we use a pair of ASCA spectra from a single epoch. Our spin estimate for the black hole primary using the continuum-fitting method is −0.11 < a* < 0.71 (90 per cent confidence), with a most likely spin of a*= 0.34. In obtaining this result, we have thoroughly explored the dependence of the spin value on a wide range of model-dependent systematic errors and observational errors; our precision is limited by uncertainties in the distance and orbital inclination of the system. For the Fe-line method, our estimate of spin is a*= 0.55+0.15− 0.22. Combining these results, we conclude that the spin of this black hole is moderate, a*= 0.49+0.13− 0.20, which suggests that the jet activity of this microquasar is powered largely by its accretion disc rather than by the spin energy of the black hole.

Keywords: accretion, accretion discs; black hole physics; stars: individual: XTE J1550−564; X-rays: binaries

Journal Article.  15402 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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