Evidence for a Black Hole Spin-Orbit Misalignment in the X-Ray Binary Cyg X-1




Zdziarski Andrzej A., Veledina Alexandra, Szanecki Michał, Green David A., Bright Joe S., Williams David R. A.

PublisherIOP Publishing Ltd

2023

Astrophysical Journal Letters

ASTROPHYSICAL JOURNAL LETTERS

ASTROPHYS J LETT

L45

951

2

8

2041-8205

2041-8213

DOIhttps://doi.org/10.3847/2041-8213/ace2c9

https://doi.org/10.3847/2041-8213/ace2c9

https://research.utu.fi/converis/portal/detail/Publication/180462039



Recently, the accretion geometry of the black hole X-ray binary Cyg X-1 was probed with the X-ray polarization. The position angle of the X-ray-emitting flow was found to be aligned with the position angle of the radio jet in the plane of the sky. At the same time, the observed high polarization degree could be obtained only for a high inclination of the X-ray-emitting flow, indicating a misalignment between the binary axis and the black hole spin. The jet, in turn, is believed to be directed by the spin axis; hence, a similar misalignment is expected between the jet and binary axes. We test this hypothesis using very long (up to about 26 yr) multiband radio observations. We find a misalignment of 20°–30°. However, contrary to the earlier expectations, the jet and binary viewing angles are found to be similar, while the misalignment is seen between the position angles of the jet and the binary axis on the plane of the sky. Furthermore, the presence of the misalignment calls into question our understanding of the evolution of this binary system.


Last updated on 2024-26-11 at 12:36