1. Finding Fast Pulsars Today andTomorrow Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Jason Hessels McGill University Pulsar Group www.physics.mcgill.ca/~pulsar Montreal, Quebec, Canada

2. Outline Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 1. What kind of pulsars do we need? 2. What is the current known population? 3. What are the best pulsars currently? 4. What selection effects are there? 5. What surveys are completed, ongoing, or planned? 6. Conclusion: What can we hope to find in the next few years?

3. 1. What kind of pulsars do we need? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Fast millisecond pulsars (P ~ 1-10ms) Bright (> a few mJy at 1400 MHz) Independently get position via VLBI? Narrow pulse profile cf. J1909-3744: duty cycle 43us!!! Extremely stable rotation (ideally over a long timescale) Proximity to Earth Measure parallax

4. 1. What kind of pulsars do we need? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Outside globular cluster? GC pulsars are generally far (therefore faint) and the GC potential affects observed period derivative. These pulsars would ideally be distributed isotropically on the sky.

5. 2. What is the current known population? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Pulsars with P < 10ms: 42 known in the Galactic field > 80 in globular clusters Of the field MSPs, only 17 have S400 > 10mJy / S1400 > 1mJy Arecibo Sky (0 o <dec<40 o ): 16 inc. B1937+21 Parkes Sky (dec < 0 o ): 24 inc. J0437- 4715 Green Bank Sky (dec > 40 o ): 2 J0218+4232, J1012+5307

6. 3. What are the best pulsars currently? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 J0437-4715: P = 5.76ms DM=2.6 pc cm-3 D~140pc S400 = 550mJy S1400 = 137mJy Binary J1713+0747: P = 4.57ms DM=16.0 pc cm-3 D~1.1kpc S400 = 36mJy S1400 = 3mJy Binary B1855+09: P = 5.36ms DM=13.3 pc cm-3 D~910pc S400 = 31mJy S1400 = 4mJy Binary J1909-3744: P = 2.95ms DM=10.4 pc cm-3 D~820pc S400 = ? S1400 = ~3mJy Binary B1937+21: P = 1.56ms DM=71.0 pc cm-3 D~3.6kpc S400 = 240mJy S1400 = 16mJy Isolated

7. 4. What selection effects are there against finding these? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 2/3 of MSPs are in binary systems An orbit causes power to be spread over numerous bins in the Fourier domain. There are techniques that search orbital parameter space to partially recuperate the lost signal strength.

8. 4. What selection effects are there against finding these? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Dispersion smearing: Given some observing bandwidth, the pulse will arrive at higher frequencies before it arrives at lower frequencies. This effect is most severe at low frequency.

9. 4. What selection effects are there against finding these? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Scattering: Multi-path propagation through irregularities in the ISM gives an intrisincally narrow pulse an exponential tail. Effect is most severe at high DM and low frequency. Pulse Width: Yikes! Sweet!(thin screen)

10. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Parkes Southern Pulsar Survey (436 MHz): (Manchester et al. 1996, Lyne et al. 1998) Entire southern hemisphere covered 17 MSPs found Smin ~ 35/6 mJy on/off the Galactic plane for a 3-ms pulsar at zero DM. Jodrell 70-cm Survey (411 MHz): (Nicastro et al. 1995) Covered dec > 35 o Survey dogged by interference One pulsar found

11. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Green Bank 140-ft Survey for Fast Pulsars (370 MHz): (Sayer, Nice & Taylor 1997) 77% of northern hemisphere covered Based on this survey, it is unlikely that there is a northern equivalent to J0437-4715 2nd Cambridge Survey (81.5 MHz): (Shrauner et al. 1995) Covered most of the sky at dec > -20 o “If pulsars like J0437-4715 were scattered all over the northern hemisphere, we would have detected more than half of them”

12. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Parkes Multibeam Galactic Plane Survey (1374 MHz): (Manchester et al., Faulkner et al. 2004) Within +/-5 o of the Galactic plane, -100 o < l < 50 o About a dozen MSPs with P < 10ms found. Swinburne Mid & High Latitude Surveys (1374 MHz): Mid-lat. (Edwards et al. 2001): 5 o < |b| < 15 o, -100 o < l < 50 o Discovered 8 recycled pulsars High-lat. (Jacoby et al. 2004): 15 o < |b| < 30 o, -100 o < l < 50 o Discovered 7 recycled pulsars

13. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Arecibo L-band Feed Array Surveys (1400 MHz): (Cordes et al. 2005, submitted) 7-beam receiver. Start with Galactic plane, but higher-latitude surveys are planned. Detailed simulations indicate that a plane survey (-5 o < b < 5 o ) will discover 30-50 MSPs. This part of the survey has already begun and should be complete in 5-7 years.

14. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Arecibo L-band Feed Array Surveys (1400 MHz): (Cordes et al. 2005, submitted) Future surveys extending the coverage to 15 o above and below the plane should discover another 20-30 MSPs. Such a mid-latitude survey was proposed for at the last Arecibo proposal deadline, and could begin later this year.

15. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 350-MHz Surveys at the GBT: (Swindburne, McGill/NRAO) GBT beam at 350 MHz is ~0.6 o 50 MHz of clean bandwidth at 350 MHz Pilot surveys, using the SPIGOT card and the CGSR coherent machine have begun at low and high Galactic latitudes at dec > 35 o This portion of the sky has not been well surveyed, and may still contain a number of relatively bright MSPs.

16. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005

17. 5. What surveys have been recently completed, are ongoing, or are planned? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 W = 0.08 alpha = -1.6 DMs =20,50 & 100

18. 6. Conclusion: What can we hope to find in the next few years? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 Very bright MSPs: J0437-4715 is unique. It is unlikely that we will find another very bright MSP at such a low DM. Previous all-sky surveys may have missed bright (S1400 > 5mJy) MSPs with DM > 80 pc cm -3 Ongoing surveys with better spectral resolution are more sensitive to MSPs with 80 pc cm -3 < DM < 150 pc cm -3.

19. 6. Conclusion: What can we hope to find in the next few years? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 MSPs in the Arecibo sky: There is the possibility of finding as many as 80 MSPs in the Arecibo sky in the next 5+ years using the Arecibo L-band Feed Array (ALFA). MSPs in the GBT sky: Low-frequency surveys covering large areas of the GBT sky will likely greatly increase the number of MSPs known above 40 o declination (currently only 2 are known with P < 10ms).

20. 6. Conclusion: What can we hope to find in the next few years? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 MSPs in the southern sky: Most of the sky above 30 o from the Galactic plane has not been surveyed to the sensitivity achieved by other Parkes multibeam surveys. Although the Parkes multibeam Galactic plane survey found an unprecedented number of pulsars, it lacked the spectral resolution to find MSPs at high DM.

21. 6. Conclusion: What can we hope to find in the next few years? Pulsar Timing Array - A Nanohertz Gravitational Wave Telescope July 21-23, 2005 MSPs in the southern sky: Discussion in Canada about building a 200- m SKA prototype, the “Canadian Large Adaptive Reflector” (CLAR). 350-MHz survey planned with the Giant Meter-Wave Radio Telescope (GMRT) in India, which has a collecting area comparable to Arecibo. For info on SKA, see Jim Corde’s talk!