Clumpy Wind Accretion in Cygnus X-1
Abstract
Cygnus X-1 is one of the brightest X-ray sources observed and shows the X-ray intensity variations on timescales 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 supergiant 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2020
- DOI:
- 10.3847/1538-4357/abba1b
- arXiv:
- arXiv:2009.09121
- Bibcode:
- 2020ApJ...904...21P
- Keywords:
-
- High mass x-ray binary stars;
- Accretion;
- black hole physics;
- Stellar winds;
- General relativity;
- Gravitation;
- Hydrodynamical simulations;
- X-ray transient sources;
- 733;
- 14;
- 159;
- 1636;
- 641;
- 661;
- 767;
- 1852;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 16 pages, 10 figures, 2 tables, accepted for publication in ApJ