Upper limits on gravitational wave emission from 78 radio pulsars

We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO 600 gravitational wave detectors. The data from both runs have been combined coherently to maximize sensitivity. For the first time, pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor of 10. For example, our tightest upper limit on the gravitational strain is $2.6\times {10}^{-25}$ for PSR $\mathrm{J}1603-7202$, and the equatorial ellipticity of PSR $\mathrm{J}2124–3358$ is less than ${10}^{-6}$. Furthermore, our strain upper limit for the Crab pulsar is only 2.2 times greater than the fiducial spin-down limit.

Figure 1

Median strain amplitude spectral density curves for the LIGO and GEO 600 interferometers during the S4 run.

Figure 2

The marginalized posterior pdfs for the four unknown pulsar parameters $h_0$, ${\varphi }_0$, $\cos \iota$, and $\psi$, for PSR $\mathrm{J}0024-7204\mathrm{C}$ using the joint data from the three LIGO detectors over S3 and S4.

Figure 3

The values of ${\Delta }_8$ for our selection of pulsars with measured $\ddot{\nu }$.

Figure 4

Histograms of the log of amplitude, ellipticity, and ratio of spin-down to gravitational wave upper limits for the combined LIGO S3 and S4 run.

Figure 5

The combined S3 and S4 upper limit results on the amplitude of gravitational waves for 76 pulsars using LIGO data compared to the joint sensitivity curve.

Figure 6

The moment of inertia–ellipticity plane for the Crab pulsar over the S2, S3, and S4 runs. The areas to the right of the diagonal lines are the experimentally excluded regions. The horizontal lines represent theoretical upper and lower limits on the moment of inertia as mentioned in Sec. 6b. Theoretical upper limits on the ellipticity are much more uncertain, the highest being a few times ${10}^{-4}$.

Figure 7

The pdfs of $h_0$ and ${\varphi }_0$ for 10 isolated pulsar injections into the LIGO detectors during S3. The anomaly seen in Pulsar7 is discussed in the text.

Figure 8

The pdfs of $h_0$ and ${\varphi }_0$ for 10 isolated and 2 binary pulsar injections into the LIGO detectors during S4.