A&A 384, 532-544 (2002)

DOI: 10.1051/0004-6361:20020052

## Searching for pulsars in close circular binary systems

**S. Jouteux**

^{1}, R. Ramachandran^{1, 2}, B. W. Stappers^{2}, P. G. Jonker^{1}and M. van der Klis^{1}^{1}Sterrenkundig Instituut "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands

^{2}Stichting ASTRON, Postbus 2, 7990 AA Dwingeloo, The Netherlands

(Received 4 September 2001 / Accepted 10 January 2002)

** Abstract **

We present a detailed mathematical analysis of the
Fourier response of binary pulsar signals whose frequencies are
modulated by circular orbital motion. The fluctuation power spectrum of
such signals is found to be
-periodic over a compact
frequency range, where
denotes orbital frequency.
Subsequently, we consider a wide range of binary systems with circular
orbits and short orbital periods, and present a Partial Coherence
Recovery Technique for searching for binary millisecond X-ray and radio
pulsars. We use numerical simulations to investigate the detectability
of pulsars in such systems with
hours, using
this technique and three widely used pulsar search methods. These
simulations demonstrate that the Partial Coherence Recovery Technique is
on average several times more sensitive at detecting pulsars in close
binary systems when the data span is more than 2 orbital periods. The
systems one may find using such a method can be used to improve the
constraints on the coalescence rate of compact objects and they also
represent those systems most likely to be detected with gravitational
wave detectors such as LISA.

**Key words:**methods: data analysis

**--**methods: numerical

**--**stars: neutron

**--**pulsars: general

Offprint request: R. Ramachandran, ramach@astro.uva.nl

SIMBAD Objects

**©**

*ESO 2002*