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S.M. Ransom (Harvard University)
We have developed two new methods for finding binary pulsars that search complementary portions of parameter space. Both techniques examine small regions of the Fourier transform of a time series and identify the distinctive but very low signal-to-noise patterns produced by binary pulsars. The first technique is a Fourier-domain version of traditional ``acceleration'' searches which can coherently detect a binary pulsar if the orbital period is much longer (approximately 10 times or more) than the observation time. Based on Fourier-domain matched filtering, it provides sensitivities similar to time-domain versions, but with great computational advantages (i.e. greatly decreased memory usage, increased speed, and an inherently parallel nature) when the time series is many hundreds of millions of points long. The second technique is a computationally ``cheap'' but incoherent search for binary pulsars where the orbital period is less than the observation duration. This search detects periodic sidebands created by orbital phase modulation of a binary pulsar's signal using a two-stage Fourier analysis. Sideband searches have the potential to detect very interesting exotic pulsar systems in ultra-compact binaries that would be impossible to detect using traditional techniques. We have implemented both searches along with many other advanced Fourier ``tricks'' into a suite of pulsar search software called PRESTO. Using this software we have discovered a very interesting 3 ms binary pulsar with a 102 m orbital period and a ~10 MJupiter companion in the globular cluster NGC6544, a most-likely isolated 4.71 ms pulsar in the globular cluster Terzan5, and have confirmed the new 65.6 ms X-ray pulsar discovered in the supernova remnant 3C58.
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