Determining the spin of two stellar-mass black holes from disc reflection signatures |
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Authors: | R. C. Reis A. C. Fabian R. R. Ross J. M. Miller |
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Affiliation: | Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA;Physics Department, College of the Holy Cross, Worcester, MA 01610, USA;Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109, USA |
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Abstract: | We present measurements of the dimensionless spin parameters and inner-disc inclination of two stellar-mass black holes. The spin parameter of SWIFT J1753.5−0127 and GRO J1655−40 is estimated by modelling the strong reflection signatures present in their XMM–Newton observations. Using a newly developed, self-consistent reflection model which includes the blackbody radiation of the disc as well as the effect of Comptonization, blurred with a relativistic line function, we infer the spin parameter of SWIFT J1753.5−0127 to be 0.76+0.11−0.15 . The inclination of this system is estimated at 55°+2−7 . For GRO J1655−40, we find that the disc is significantly misaligned to the orbital plane, with an innermost inclination of 30°+5−10 . Allowing the inclination to be a free parameter, we find a lower limit for the spin of 0.90, this value increases to that of a maximal rotating black hole when the inclination is set to that of the orbital plane of J1655−40. Our technique is independent of the black hole mass and distance, uncertainties in which are among the main contributors to the spin uncertainty in previous works. |
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Keywords: | accretion, accretion discs black hole physics X-rays: individual: J1753.5−0127, J1655−40 |
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