1. Coherent Dedispersion Pulsar Timing Machines Matthew Bailes + Swinburne, Caltech, ATNF, CASPER

2. Magnetic Field - Period Diagram Crab pulsar Pulsars go this way “Noisy” “Smooth”

3. Timing Procedure: “Fold” data at apparent Period (up to ~million pulses)  Use pulsar ephemeris, site position Calculate shift Calculate Site Arrival Time (SAT) Correct for Clocks (UT, UT1, etc) Transform to Solar System Barycentre (SSB)  Barycentric arrival time (BAT/TOA) Subtract pulsar model Fit for pulsar parameters

4. Pulsar Timing Count the Pulses!

5. PSR J1600-3053 Form a Profile Cross Correlate Get time of arrival

6. Time of Arrival (TOA) error width Signal to noise ratio Gaininformation PSR flux Temperature

7. Pulse Dispersion FFT x Filter -1 FFT -1 No Dispersion!

8. Pulsar (in)Coherent Dedispersion Uses computers/FPGAs and digitizers to remove dispersion almost “perfectly” Rules:  Don’t distort profiles  Have high dynamic range  Attain Polarisation Purity  Remove Dispersion changes  Don’t change any equipment  Tension!

9. Radioastronomy in Software No hard definition Pulsar “backend” written in software, not hardware Requires:  Digitizer  IO system to computers  Software Advantages:  Bandwidth follows Moore’s law

10. Radio Astronomy in Software Finite amount of information:  ~B N tel N p (voltages/second) ~ giga-samples/sec To make spectra for a Single dish:  ~N p 5 log 2 N FFT B PKS 512 MHz, 1024 channels, 2 polns  2x50x512x10 6 ~50 GFlops!  Mpt FFTs ~500 Gflops  Gpt FFTs ~ Teraflops

11. Example: Chart Recorder (power monitor):

12. RFI detector (not real code - contains bug!)

13. S2TCI Model (van Straten + Wiedtfeld?) York A/D Processors 8 Video Tapes 8 Video Tapes CPU 2 x 16 MHz 128 Mb s -1 Mark I Switch

14. Issues Error rate ~10 -5 Required two custom devices (@70K each) 1000s of video tapes required Limited BW Playback < real time Months until result

15. CPSR1 Model (Anderson/van Straten) Caltech A/D Processors COTS Disk COTS DLT Tapes COTS 2 x 20 MHz 160 Mb s -1 SUN COTS DLT Tapes COTS Switch COTS

16. CPSR1 Issues Error rate ~10 -5 -> Zero 1000s of DLT tapes required (5K/day) No custom playback unit required Still Limited BW Playback < real time Weeks until result

17. Processors Custom A/D RAM Dell CPSR2 Model (Bailes/Ord/ van Straten/Hotan) 2 x 2 x 64 MHz 1024 Mb s -1 Real time +5 mins Caltech A/D RAM DellSwitch

18. CPSR2 Real time RFI excision (< hour to implement) 5 minute delay until profiles cf weeks-months Much greater sensitivity (~20 MSPs) 2bit device (worse residuals on 0437!) Running since Aug 2002-now Gb/s VLBI recorder CGSR unreliable (COTS too cheap)

19. Best Results?? Typically few to ~100 ns RMS 0437-4715  van Straten et al. (130 ns) 3 years 1713+0747  Nice et al. (200 ns) (Arecibo)  Verbiest et al. (2009) 200 ns (Parkes) 0437-4715  Verbiest et al. (2008) 200ns 9.9 years 1909-3744  Verbiest et al. (2009) 166 ns ~6 years

20. Pulsar Profiles with Zero Smearing PSR J0437-4715 timing Joris Verbiest PhD 5.75 ms

21. Verbiest et al. (2008) Incoherent S2 CPSR2 CPSR1

22. Pulsar Parameters

23. PSR J0437-4715 Changing inclination angle  di/dt (10,000 sigma!) Annual “orbital” parallax  i=137.58(6) deg!  GR “test” van Straten et al. (2001) Mass of a white dwarf  Mc=0.25(1) dP b /dt= 200 sigma 100,000 sigma 5,000,000 sigma

24. PSR J0437-4715 (Deller et al. 2008B) Parallax works! D=156.3(1.3) pc D Pb =156 (2) pc (G/G) < 2x10 -12 yr -1.

25. 0437 Results (Deller et al 2008) No anomalous accelerations Three different distance measures accurate to 1-2%  Parallax works! d G /d t < 2x10 -12 G No unseen “Jupiters” within 226 AU No black holes/neutron stars approaching No extreme gravitational wave background

26. PSR J1909-3744 40  s wide!!

28. Shapiro Delay

29. Astrophysics: e = 1.3(2) x 10 -7 a = 569,397.318 km (a-b) = 5  M 2 = 0.212(4) Mo D = 1260 pc

31. Giant Pulses (Knight et al. 2006) Unresolved on us timescales From young or millisecond pulsars Power-law distribution of energies MWA  Bhat et al. (2007) < 2  s wide!

32. DFB3 DFB3 (Manchester/Hampson/Brown) APSR (Bailes/van Straten/Jameson) CABB A/D 2 x 16 x 64 MHz 8096 Mb s -1 8 Gb s -1 PFB PFB -1 Switch Processors APSR

33. APSR Issues/Features 10 seconds until profile 1 GHz BW @ 2 bits coherent dedispersion 512 MHz BW @ 4 bits coherent dedispersion 256 GHz BW @ 8 bits coherent dedispersion Adaptive RFI cancellation mode (Kesteven & Manchester) Coherent filterbank & fold for >= 20 pulsars at once! Single pulse mode, RT calibration Very robust, jetisons to disk if required 64 MHz/Server real time ! BUT… PFB “staining”

36. DFB3 + lightening

37. APSR + lightening

38. DM = 120, 3 ms MSP with APSR

40. Key Software PSRDADA  Open source ring buffers and resends DSPSR  Open source coherent dedisperser  Links to ring buffer or disk files  Writes psrchive files  Nehalem 128 MHz, real time coherent dedispersion! PSRCHIVE  Open source pulsar profile manipulator

41. A/D RAM CPU Processors CASPSR Model (van Straten/Jameson) 2 x 400 MHz (8 bit) No PFB stains RAM 12,800 Mb s -1 12.8 Gb s -1 Switch CPU

42. CASPSR/TerryBOB Issues/Features FFTs become enormous Expect ~1 minute delay until profiles seen NO PFB issues!!! On edge for Clovertown @ 2 servers Very extendable  N servers if required Moore’s law on our side

45. Future: ROACHPSR?  800(1024) MHz BW x 2 x 8 bits  24 port 10 Gb Switch  4-6 Data streamers (Nehalems with 48 GB RAM)  8-12 Processors (Supermicros with 2xGPUs) 2-3 x CASPSR  RFI excision/removal 13xCASPSR beam spectrometer?  200 MHz out of 400 MHz, 2 bits

46. Parkes 13 beam x 400 MHz  Pulsars  Spectroscopy 10cm spectroscopy  1024 MHz, 8192 channels 13cm spectroscopy  512 MHz 10/50cm timing  3 GHZ @ 1024 MHz  700 MHz @ 64 MHz VLBI