English

Clumpy wind accretion in Cygnus X-1

High Energy Astrophysical Phenomena 2020-11-20 v1

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.

Keywords

Cite

@article{arxiv.2009.09121,
  title  = {Clumpy wind accretion in Cygnus X-1},
  author = {Ishika Palit and Agnieszka Janiuk and Bozena Czerny},
  journal= {arXiv preprint arXiv:2009.09121},
  year   = {2020}
}

Comments

16 pages, 10 figures, 2 tables, accepted for publication in ApJ

R2 v1 2026-06-23T18:39:25.165Z