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Table 4.

Local (z ∼ 0) merger rate densities [Gpc−3 yr−1] for different BH-BH formation scenarios.

No. BH-BH formation scenario M480.B M481.B M380.B
1. MT1(1/2/4/5-1/4)/MT2(7-4) BH1 MT2(14-2/4/5/7/8) BH2 83.1 0.4 0.3
2. MT1(1/2/4-1) BH1 MT2(14-2/4) SW CE2(14-4/5:14-7/8/14) BH2 0.4 12.5 0.0
3. MT1(1/2/4-1) BH1 CE2(14-4/5:14-7/8/14) BH2 2.1 2.0 51.2
4. MT1(1/2/4-1) BH1 MT2(14-2/4) CE2(14-4/5:14-7/8/14) BH2 1.1 1.0 1.6
5. MT1(4-2/4) MT2(4/5/7/8-4) CE12(4/5/8-4:14-7) BH1 BH2 1.4 1.4 2.0
6. Other scenarios 0.3 0.6 6.6
Total 88.4 17.9 61.7

Notes. The main formation scenario for given model is marked in bold. MT1-stable RLOF, donor is initially more massive star; MT2-stable RLOF, donor is initially less massive star; BH1-formation of black hole by initially more massive star; BH2-formation of black hole by initially less massive star; CE1-common envelope initiated by initially more massive star; CE2-common envelope initiated by initially less massive star; CE12-double common envelope initiated by two giants; SW – switch from TTMT to CE based on the revised condition (see Sects. 3.2 and 5). The numeric types are consistent with Hurley et al. (2002): 0 – main sequence star with M ≤ 0.7 Msun (deeply or fully convective) 1 – main sequence star with M >  0.7 Msun 2 – Hertzsprung gap star 3 – first giant branch star 4 – core helium burning star 5 – early asymptotic giant branch star 6 – thermally pulsing asymptotic giant branch star 7 – main sequence naked helium star 8 – Hertzsprung gap naked helium star 9 – giant branch naked helium star 10 – helium white dwarf 11 – carbon or oxygen white dwarf 12 – oxygen or neon white dwarf 13 – neutron star 14 – black hole 15 – massless remnant. The values in the brackets (e.g., 1/2/4) refer to different possible variants of the evolutionary types of binary components during given phase. The type of an initially more massive component is given first and the type that is initially less massive component comes second (after the dash). In the case of a CE phase type, those at the onset are given as first, the next types after envelope ejection (after the colon).

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