CYG X-3: A galactic double black hole or black-hole-neutron-star progenitor

Krzysztof Belczynski, Tomasz Bulik, Ilya Mandel, B. S. Sathyaprakash, Andrzej A. Zdziarski, Joanna Mikołajewska

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There are no known stellar-origin double black hole (BH-BH) or black-hole-neutron-star (BH-NS) systems. We argue that Cyg X-3 is a very likely BH-BH or BH-NS progenitor. This Galactic X-ray binary consists of a compact object, wind-fed by a Wolf-Rayet (W-R) type companion. Based on a comprehensive analysis of observational data, it was recently argued that Cyg X-3 harbors a 2-4.5 M black hole (BH) and a 7.5-14.2 M W-R companion. We find that the fate of such a binary leads to the prompt (≲ 1 Myr) formation of a close BH-BH system for the high end of the allowed W-R mass (M W-R ≳ 13 M ). For the low- to mid-mass range of the W-R star (M W-R ∼ 7-10 M ) Cyg X-3 is most likely (probability 70%) disrupted when W-R ends up as a supernova. However, with smaller probability, it may form a wide (15%) or a close (15%) BH-NS system. The advanced LIGO/VIRGO detection rate for mergers of BH-BH systems from the Cyg X-3 formation channel is ∼10 yr -1 , while it drops down to ∼0.1 yr -1 for BH-NS systems. If Cyg X-3 in fact hosts a low-mass black hole and massive W-R star, it lends additional support for the existence of BH-BH/BH-NS systems.

Original languageEnglish
Article number96
Pages (from-to)1-7
Number of pages7
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 10 Feb 2013
Externally publishedYes


  • binaries: general
  • stars: neutron
  • X-rays: binaries

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