Bayesian estimation of pulsar parameters from gravitational wave data

We present a method of searching for, and parameterizing, signals from known radio pulsars in data from interferometric gravitational wave detectors. This method has been applied to data from the LIGO and GEO 600 detectors to set upper limits on the gravitational wave emission from several radio pulsars. Here we discuss the nature of the signal and the performance of the technique on simulated data. We show how to perform a coherent multiple detector analysis and give some insight in the covariance between the signal parameters.Comment: 9 pages, 6 figures. Accepted to Phys. Rev. D. A few small changes from previous versio

Targeted searches for gravitational waves from radio pulsars

An overview of the searches for gravitational waves from radio pulsars with LIGO and GEO is given. We give a brief description of the algorithm used in these targeted searches and provide end-to-end validation of the technique through hardware injections. We report on some aspects of the recent S3/S4 LIGO and GEO search for signals from several pulsars. The gaussianity of narrow frequency bands of S3/S4 LIGO data, where pulsar signals are expected, is assessed with Kolmogorov-Smirnov tests. Preliminary results from the S3 run with a network of four detectors are given for pulsar J1939+2134

A Metropolis-Hastings algorithm for extracting periodic gravitational wave signals from laser interferometric detector data

The Markov chain Monte Carlo methods offer practical procedures for detecting signals characterized by a large number of parameters and under conditions of low signal-to-noise ratio. We present a Metropolis-Hastings algorithm capable of inferring the spin and orientation parameters of a neutron star from its periodic gravitational wave signature seen by laser interferometric detector

Bayesian searches for gravitational waves from pulsars

Methods for searching for periodic gravitational wave signals from triaxial pulsars using interferometric gravitational wave detectors have been developed. Since the gravitational wave signals from pulsars are expected to be weak, long stretches of data must be used for any detection. Over the course of a day, and a year, these periodic signals are Doppler shifted due to the motion of the Earth. The response of the interferometers to each polarisation of gravitational waves will also give rise to an amplitude modulation of the periodic signal. These effects are taken into account and an end-to-end Bayesian scheme for making inferences from the data is presented. Several software tests have been performed to validate the core routines, such as barycentring, using independent software. The GEO 600 and LIGO interferometers had their first scientific data run (S1) for 17 days between 23 August and 9 September 2002. An analysis was carried out to search for gravitational wave signals from pulsar B1937+21. While no signals were detected, a 95% upper limit of h0 < 1.4 x 10-22 was determined using S1 data where h0 is the amplitude of the gravitational waves. Given that pulsar B1937+21 is at a distance of 3.6 kpc, and assuming a moment of inertia of 1038kg m2, the corresponding upper limit on the equatorial ellipticity was determined to be = 2.9 x 10-4. The upper limit on gravitational waves from pulsar B1937+21 using S1 data was over an order of magnitude lower than the previous best limit at the time. Data from LIGO's second science run (S2) in the spring of 2003 was analysed with the sensitivity of each detector in the network being roughly an order of magnitude better than in S1 across a large range of frequencies. Upper limits were placed on a total of 28 isolated pulsars using the S2 data. The analysis procedure for S2 was more robust to interfering spectral lines and took advantage of the longer stationarity of the S2 data. Two hardware injections of hypothetical pulsars were injected in the LIGO interferometers during S2. The successful extraction of these signals from the LIGO S2 data significantly increased our confidence in the the overall data analysis pipeline. For four of the closest pulsars their equatorial ellipticities were constrained to less than = 10-5 with 95% confidence. These limits are beginning to reach interesting ellipticities which some exotic theories suggest could be supported in neutron stars. The third science run (S3) in which GEO 600 and LIGO participated took place from late October 2003 to early January 2004. Again, the improvement in sensitivity compared to the previous run (S2) was significant. Preliminary multi-detector results were determined for the same previous 28 pulsars using S3 data. The equatorial ellipticities for 11 of these pulsars are constrained to less = 10-5 with 95% confidence. With the S3 data, the upper limit on the gravitational wave emission from the Crab pulsar was only approximately a factor of four from the upper limits inferred from the spindown of the pulsar. When this barrier is overcome the prospects of detecting gravitational waves from the Crab pulsar will become more plausible. Future work based on these implementations will examine a larger set of missing known pulsars including binary systems. Studies in Markov Chain Monte Carlo techniques may also allow the expansion this method to a larger parameter space

Detecting gravitational radiation from neutron stars using a six-parameter adaptive MCMC method

We present a Markov chain Monte Carlo technique for detecting gravitational radiation from a neutron star in laser interferometer data. The algorithm can estimate up to six unknown parameters of the target, including the rotation frequency and frequency derivative, using reparametrization, delayed rejection and simulated annealing. We highlight how a simple extension of the method, distributed over multiple computer processors, will allow for a search over a narrow frequency band. The ultimate goal of this research is to search for sources at a known locations, but uncertain spin parameters, such as may be found in SN1987A.Comment: Submitted to Classical and Quantum Gravity for GWDAW-8 proceeding