Next: Binary Pulsar Diversity and Up: Restrictions on the Scenario Previous: Phenomenological Kick Velocity
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Дата изменения: Wed Feb 26 15:09:31 1997 Дата индексирования: Tue Oct 2 14:46:02 2012 Кодировка: |
Next: Binary
Pulsar Diversity and Up: Restrictions
on the Scenario Previous: Phenomenological
Kick Velocity
Let us consider what fraction of different types of binary radiopulsars
can be obtained within the framework of the modern evolutionary scenario
of binary stars if a phenomenological kick velocity
caused by the collapse anisotropy is added. Several
attempts of this kind have been made over the last 10 years (Kornilov and
Lipunov, 1984[87]; Tutukov et
al., 1984[198]; Dewey and Cordes,
1987[45]; Bailes, 1989[7]).
The observational data existing at that time convincingly pointed to the
presence of a small kick velocity of about 70-100 km s
. However, the statistics of binary radiopulsars at that time was very
poor. Of course, all such studies are restricted considering the evolution
of an ensemble of stars that initially originated from binaries and were
not tidally captured, as occurs in globular clusters;
so the numerous binary pulsars observed in globular
clusters and whose evolution is not yet fully understood must be excluded
from consideration.
Here, we focus on the ratio of binary to single pulsars as a function of the kick velocity; use of the binary pulsar type fraction among single pulsars allows us to get rid of many poorly known pulsar parameters (such as the characteristic time of magnetic field decay). We stress that especially for binary NS the results are fully independent the decay time.
Mass loss and kick velocity are the processes leading
to binary system disruption; however, there are a number of processes connected
with the orbital momentum losses tending to bound the binary (e.g. gravitational
radiation, magnetic stellar wind).
For massive binaries (with primary mass 
), which produce the vast majority of NS in binaries, a more important
and effective process is the orbital angular momentum loss during the CE
stage. As already mentioned, a flat distribution by semi-major axes of
the binaries makes the uncertainty in 
rather insignificant. Below we put 
.
We compare the calculated (``C'') and observed (``O'') numbers of binary radiopulsars with NS (PSR+NS), WD (PSR+WD), planets (PSR+PL), and normal OB-stars (PSR+OB). The observed numbers of the binary pulsars in the galactic disk and their assumed scenario origin are presented in Table 6.
