1997/11/18 by E. Ergma, Ene Ergma, Ergma, Ene +2 · 1 citation
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Mechanics and Biomechanics Studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9711197
8 pages, Latex, 2 figures, uses psfig.sty, to appear in Astronomy and Astrophysics
arxiv created 1997/11/18 · openalex publication_date 1997/11/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
By means of population synthesis we find that the expected Galactic number of black holes with massive helium star companions is ∼ 100 and depends on an assumed threshold for Mpre-BH. The overwhelming majority of these systems has orbital periods in excess of 10 hr, with a maximum at ∼ 100 hr, while under the Illarionov & Sunyaev (1975) disk formation criteria for accretion from the strong stellar wind of Wolf-Rayet star disk accretion is possible only for orbital periods below ∼ 10 hr. However, the number of such short-period systems is vanishingly small. If the accretor in Cyg X-3 is a 10 Msun black hole, then the accretion rate will be super-Eddington. Super-Eddington accretion may be responsible for the formation of jets in Cyg X-3 and may also support an X-ray luminosity as high as ∼ 1039 erg/s. From the orbital period distribution for neutron stars with massive helium companions we find that if during the common envelope phase a neutron star accretes at Eddington rate and spins-up to the equilibrium period, then in most systems it acts as a ``propeller'' and accretion from the WR star wind is impossible. For the model with two massive helium stars as an immediate progenitor of Cyg X-3, requirement of accomodation of two WR stars in the post-common-envelope orbit combined with severe mass loss by them prevents formation of BH+WR systems with orbital periods less than several days.