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arXiv · 2009.09121

Clumpy wind accretion in Cygnus X-1

Ishika Palit·Agnieszka Janiuk·Bozena Czerny
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Abstract

Cygnus X-1 is one of the brightest X-ray sources observed and shows the X-ray intensity variations on time scales from milliseconds to months in both the soft and hard X-rays. The accretion onto the black hole is believed to be wind fed due to focused stellar wind from the binary companion HDE-226868. We aim to understand the physical mechanism responsible for the short timescale X-ray variability ($<$100 s) of the source in its Hard/Low state. We compute the 2D relativistic hydrodynamic simulation of the low angular momentum accretion flow with a time dependent outer boundary condition that reflects the focused, clumpy wind from the super-giant in this X-ray binary system. We follow the dynamical evolution of our model for about 100 s and present the results showing an oscillatory shock, being a potential explanation of variability observed in hard X-rays. The simulated model with shock solutions is in good agreement with the observed power density spectra of the source.

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Ishika Palit, Agnieszka Janiuk, Bozena Czerny. 2020-09-18. Clumpy wind accretion in Cygnus X-1. https://doi.org/10.3847/1538-4357%2Fabba1b

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