Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1

Abstract

Cygnus X-1 is a well-studied persistent black hole X-ray binary. Recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass $M$, the orbital inclination $i$ and the source distance $D$, have been updated. In this work we redetermine the spin parameter using the continuum-fitting technique for those updated parameter values. Based on the assumption that the spin axis of the black hole is aligned with the orbital plane, we fit the thermal disk component to a fully relativistic thin accretion disk model. The error in the spin estimate arising from the combined observational uncertainties is obtained via Monte Carlo (MC) simulations. We demonstrate that, without considering the counteracting torque effect, the new spin parameter is constrained to be a${}_{\ast }>0.9985$ (3$\sigma$), which confirms that the spin of the black hole in Cygnus X-1 is extreme.

ApJ published

References in corpus (8)

• Constraining Black Hole Spin Via X-ray Spectroscopy
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• A Determination of the Spin of the Black Hole Primary in LMC X-1
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• Hypercritical Accretion for Black Hole High Spin in Cygnus X-1
• AstroSat and MAXI view of Cygnus X-1: Signature of an `extreme' soft nature
• The spectral-timing analysis of Cygnus X-1 with Insight-HXMT
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