6 Summary and Future Prospects 

The main aim of this article was to review, from an observational perspective, some of the many astrophysical applications provided by the present sample of binary and millisecond radio pulsars. In writing this article I hope that many of the broad-ranging results in this field were covered and that it will be of use as a starting point for those wishing to explore the vast body of literature that presently exists.

Through an understanding of the Galactic population of radio pulsars summarised in § 3, it is possible to predict the detection statistics of terrestrial gravitational wave detectors to nearby rapidly spinning neutron stars (§ 3.3), as well as coalescing binary neutron stars at cosmic distances (§ 3.4). I look forward to the continued improvements in gravitational wave detector sensitivities. These should result in a number of interesting developments and contributions in this area. These developments and contributions might include the detection of presently known radio pulsars, as well as a population of coalescing binary systems which have not yet been detected as radio pulsars.

The phenomenal timing stability of radio pulsars leads naturally to a large number of applications, including their use as laboratories for relativistic gravity (§ 4.3) and as natural detectors of gravitational radiation (§ 5). Long-term timing experiments of the present sample of millisecond and binary pulsars currently underway appear to have tremendous potential to dig more deeply in these areas and perhaps detect the gravitational wave background (if it exists) in the next 5-10 years.

These and other applications will benefit greatly from the continued discovery of new systems by the present generation of radio pulsar searches. These searches continue to probe new areas of parameter space. Based on the results presented in § 3.3, it is clear that we are aware of only about 1% of the total active pulsar population in our Galaxy. Thus, in terms of the exotic systems that exist, we have almost certainly not seen all of the pulsar zoo. I look forward to the discovery of a number of unexpected systems in the coming years....perhaps a dual-line binary pulsar, a neutron star with a black hole companion, as well as the exciting possibility of sub-millisecond pulsars.

Binary and Millisecond Pulsars D. R. Lorimer (dunc@mpifr-bonn.mpg.de) http://www.livingreviews.org/lrr-1998-10 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de