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At present, the following facts are known about
double degenerate compact binaries in our Galaxy:
Table: BH Candidates (Cherepashchuk ).
Table: Binary PSR with NS secondaries (Nice et al. )
- A few binary radiopulsars are known to have the secondary NS
component (Table ).
- Three of these binary pulsars must coalesce
due to the orbital angular momentum removal by GW
on a time scale shorter than the age of the Universe (the
Hubble time yr).
- No binary pulsars with BH is known as yet (although
from evolutionary considerations one may expect one such
an object to be formed in the Galaxy per about 1000 single
pulsars, Lipunov et al. )
- No binary BH has been found so far.
- In contrast, 10 BH candidates are already known in
X-ray binary systems with normal companions . Their parameters
are listed in Table . Note that the mean BH mass
in these systems is
< M , i.e. BH formed in stellar evolution
are notably more massive than NS (with the typical mass
Fri Nov 28 17:12:56 MSK 1997