On the formation and evolution of the first Be star in a black hole binary MWC 656

Grudzinska, M.; Belczynski, K.; Casares, J.; de Mink, S. E.; Ziolkowski, J.; Negueruela, I.; Ribó, M.; Ribas, I.; Paredes, J. M.; Herrero, A.; Benacquista, M.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 452, Issue 3, p.2773-2787

Advertised on:
9
2015
Number of authors
11
IAC number of authors
2
Citations
31
Refereed citations
26
Description
We find that the formation of MWC 656 (the first Be binary containing a black hole) involves a common envelope phase and a supernova explosion. This result supports the idea that a rapidly rotating Be star can emerge out of a common envelope phase, which is very intriguing because this evolutionary stage is thought to be too fast to lead to significant accretion and spin up of the B star. We predict ˜10-100 of B-BH binaries to currently reside in the Galactic disc, among which around 1/3 contain a Be star, but there is only a small chance to observe a system with parameters resembling MWC 656. If MWC 656 is representative of intrinsic Galactic Be-BH binary population, it may indicate that standard evolutionary theory needs to be revised. This would pose another evolutionary problem in understanding black hole (BH) binaries, with BH X-ray novae formation issue being the prime example. Future evolution of MWC 656 with an ˜5 M⊙ BH and with an ˜13 M⊙ main-sequence companion on an ˜60 d orbit may lead to the formation of a coalescing BH-NS (neutron star) system. The estimated Advanced LIGO/Virgo detection rate of such systems is up to ˜0.2 yr-1. This empirical estimate is a lower limit as it is obtained with only one particular evolutionary scenario, the MWC 656 binary. This is only a third such estimate available (after Cyg X-1 and Cyg X-3), and it lends additional support to the existence of so far undetected BH-NS binaries.
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