1. Detecting the Gravitational Wave background using Millisecond Pulsars Fredrick A. Jenet Center for Gravitational Wave Astronomy University of Texas at Brownsville

2. Collaborators Dick Manchester ATNF/CSIRO Australia George Hobbs ATNF/CSIRO Australia KJ Lee Peking U. China Andrea Lommen Franklin & Marshall USA Shane L. Larson Penn State USA Linqing Wen AEI Germany Teviet Creighton Caltech USA John Armstrong JPL USA

3. What can we do with an array of pulsars and the G-wave background? 1.Make a definitive detection of G-waves. 2.Measure the polarization properties of G-waves. 3.Place limits on the graviton mass. 4.Study the properties of the G- wave source.

4. The most likely source of G-waves will be a stochastic background generated by super-massive binary black holes distributed throughout the universe! Jaffe & Backer (2002) Wyithe & Lobe (2002) Enoki, Inoue, Nagashima, Sugiyama (2004) Like the cosmic micro-wave background, the G-wave background is an incoherent sum of G-waves. h c = A f -   = 2/3 A = 10 -15 to 10 -14 yrs -2/3

5. Detecting G-waves The presence of G-waves will cause the rate of arrival a individual pulses to fluctuate.

6. kk  Photon Path G-wave Pulsar Earth

7. Important Points

8. The timing residuals for a stochastic background This is the same for all pulsars. This depends on the pulsar. The induced residuals for different pulsars will be correlated.

9. Two-point correlation Two basic techniques Spherical Harmonic Decomposition Hellings & Downs 1983 Jenet, Hobbs, Lee, & Manchester 2005 Hellings 1990 Jaffe & Backer 2002

10. Single Pulsar Limit (1  s, 7 years) Expected Regime For a background of SMBH binaries: h c = A f -2/3

11. Single Pulsar Limit (1  s, 7 years) 1  s, 1 year (Current ability) Expected Regime For a background of SMBH binaries: h c = A f -2/3

12. Single Pulsar Limit (1  s, 7 years) 1  s, 1 year (Current ability) Expected Regime.1  s 5 years For a background of SMBH binaries: h c = A f -2/3

13. Single Pulsar Limit (1  s, 7 years) 1  s, 1 year (Current ability) Expected Regime.1  s 5 years.1  s 10 years For a background of SMBH binaries: h c = A f -2/3

14. Single Pulsar Limit (1  s, 7 years) 1  s, 1 year (Current ability) Expected Regime.1  s 5 years.1  s 10 years SKA 10 ns 5 years 40 pulsars For a background of SMBH binaries: h c = A f -2/3

15. Single Pulsar Limit (20 ns, 2 years) 1  s, 1 year (Current ability) Expected Regime.1  s 5 years.1  s 10 years SKA 10 ns 5 years 40 pulsars For a background of SMBH binaries: h c = A f -2/3

16. G-wave polarization properties

17. Graviton Mass Current solar system limits place m g < 4.4 10 - 22 eV  2 = k 2 + (2  m g /h) 2 < 1/ (4 months) Detecting 5 year period G-wave reduces the upper bound of the graviton mass by a factor of 15.