6.3 Going further
The most important future observations include:
- Routine increase of the statistics of binary pulsars, especially with low radio luminosity. This
will allow one to put stronger constraints on the NS + NS merger rate as directly inferred from
the binary pulsars statistics. More indirectly, a larger sample of NS parameters in binary pulsars
would be useful for constraining the range of parameters of scenarios of formation for double
NSs and, hence, a better understanding their origin (see, for example, a recent attempt of such
an analysis in ).
- Discovery of a possible NS + BH binary. Measurements of its parameters would be crucial for
models of formation and evolution of BHs in binary systems in general. Current estimates of
the number of such binaries in the Galaxy, obtained by the population synthesis method, range
from one per several thousand ordinary pulsars [230, 222] to much smaller values of about
0.1 – 1% of the number of double NSs in the Galactic disk .
- Search for unusual observational manifestations of relativistic binaries (e.g., among some new
radio transient sources like GCRT J1745–3009, firm identifications with
some GRBs, etc.)
- Improving the estimates of binary merger rate limits from data taken by GW detectors.
The most important theoretical issues include:
- Stellar physics: post-helium burning evolution of massive stars, supernova explosion mechanism,
masses of compact stars formed in the collapse, mechanism(s) of kick velocity imparted to
nascent compact remnants (neutron stars and black holes), stellar winds from hydrogen- and
- Binary evolution: treatment of the common envelope stage, magnetic braking for low-mass
binaries, observational constraints on the initial distributions of orbital parameters of binary
stars (masses, semimajor axes, eccentricities).
- Last but not least, it is very important to improve our knowledge of such “traditional” topics
of stellar astronomy as the fraction of binary stars among the total population, distributions
of binary stars over separations of components, and their mass ratios.