1. The Extreme Dimension: Time-Variability and The Smallest ISM Scales Dan Stinebring Oberlin College

2. Some key collaborators Jim Cordes Barney Rickett, Bill Coles (UCSD) Maura McLaughlin (discovery paper) Oberlin college students...

3. Lorimer&Kramer (LK) Fig. 4.2 Sketch showing inhomogeneities in the ISM that result in observed scattering and scintillation effects.

4. 1133+16 dyn & sec logarithmic grayscale linear grayscale

5. 1133+16 dyn & sec logarithmic grayscale linear grayscale dynamic (or primary) spectrum secondary spectrum

6. Coherent radiation scatters off electron inhomogeneities ~ 1 kpc ~ 10 mas

7. Multi-path interference causes a random diffraction pattern

8. Relative transverse velocities produce a dynamic spectrum time

9. Scattering in a thin screen plus a simple core/halo model can explain the basics of scintillation arcs

10. Time variability of scintillation arcs will allow probing of the ISM on AU size scales

11. Kolmogorov vs. Gaussian PSF How to produce a “core/halo” psf? A Gaussian psf will NOT work: No halo.

12. Kolmogorov vs. Gaussian PSF Kolmogorov turbulence DOES work It produces a psf with broad wings

13. The substructure persists and MOVES! Arecibo observations January 2005

14. Hill, A.S., Stinebring, D.R., et al. 2005, ApJ,619, L171 This is the angular velocity of the pulsar across the sky! 51 ± 2 mas/yr

15. Brisken dyn + secondary 1.2 Walter Brisken (NRAO) et al. “Small Ionized and Neutral Structures,” Socorro, NM, 2006 May 23

16. B1737+13 movie Ira asked about the anisotropy of the turbulence...

17. Cumulative Delay - Arclets

18. time delays scale as Kolmogorov:

19. Arecibo is the best! Raw sensitivity is essential Excellent instrumentation Some bands (e.g. 327 MHz) have low RFI (small, focused projects are the key...)

20. A new result... 6 months of ~ weekly Arecibo observations of a moderate DM pulsar (B1737+13) 4 x 50 MHz bands near 21 cm Investigate time variability of ScintArc structure and its effect on pulsar timing

21. How Does this Work?

22. conjugate time axis Conjugate time axis (heuristic) d D y V incident plane wave ( )

23. conjugate freq axis Conjugate frequency axis (heuristic) D incident plane wave ( )

24. where do the parabolas come from ?” Where do the parabolas come from?

25. parabola eqn on data plot B2021+25

26. Walker et al. 2004 1d “image” on the sky where do the arclets come from ?” Where do the “arclets” (inverted parabolas) come from?

27. Some Observational Highlights...

28. The Earth Orbits the Sun !!

29. Effective Velocity Cordes and Rickett 1998, ApJ, 507, 846

30. 1929+10 velocity plot

31. Multiple Arcs —> Multiple “Screens”

32. “Screen” Locations f =  f t 2

33. PSR 1133+16 proper motion (2d) s=0s=1 f =  f t 2

36. Can We Improve High-accuracy Pulsar Timing?

37. Detection of Gravitational Waves Prediction of general relativity and other theories of gravity Generated by acceleration of massive object(s) (K. Thorne, T. Carnahan, LISA Gallery) Astrophysical sources:  Inflation era  Cosmic strings  Galaxy formation  Binary black holes in galaxies  Neutron-star formation in supernovae  Coalescing neutron-star binaries  Compact X-ray binaries (NASA GSFC) R. N. Manchester (ATNF)

38. Detecting Gravitational Waves with Pulsars Observe the arrival times of pulsars with sub-microsecond precision. Correct for known effects (spin-down, position, proper motion,...) through a multi-parameter Model Fit. Look at the residuals (Observed - Model) for evidence of correlated timing noise between pulsars in different parts of the sky. Timing residuals for PSR B1855+09 R. N. Manchester (ATNF)

39. Cumulative Delay - No Arclets

40. 1133+16 dyn & sec D. Hemberger

41. B1737+13 tau_ss + errors (36 epochs) D. Hemberger

42. Summary Interstellar scattering allows us to probe the ISM on AU-size scales. Much of the scattering appears to be localized in thin “screens” along the line of sight. We don’t know what these screens are. There is evidence for compact (~ AU), dense (~ 100 cm -3 ) structures of unknown origin. Scattering effects are time variable and need to be corrected for in highest precision pulsar timing. LOFAR is an excellent telescope with which to pursue these studies!! Dan Stinebring Oberlin College dan.stinebring@oberlin.edu

43. Detection of Gravitational Waves Prediction of general relativity and other theories of gravity Generated by acceleration of massive object(s) (K. Thorne, T. Carnahan, LISA Gallery) Astrophysical sources:  Inflation era  Cosmic strings  Galaxy formation  Binary black holes in galaxies  Neutron-star formation in supernovae  Coalescing neutron-star binaries  Compact X-ray binaries (NASA GSFC) R. N. Manchester (ATNF)

44. Detecting Gravitational Waves with Pulsars Observed pulse periods affected by presence of gravitational waves in Galaxy (psr at time of emission; Earth at time of reception) For stochastic GW background, effects at pulsar and Earth are uncorrelated Use an array of pulsars to search for the GW background that is correlated because of its effect on the Earth (at time of reception) Best limits are obtained for GW frequencies ~ 1/T where T is length of data span Timing residuals for PSR B1855+09 R. N. Manchester (ATNF) Want to achieve < 1 us residuals for 10 pulsars for 5 years

45. R. N. Manchester Sept 2006

46. data: R. N. Manchester

47. What we measure... ISM impulse response function ISM the autocorrelation of the impulse response At the moment, we use the centroid of

48. A new result... 6 months of ~ weekly Arecibo observations of a moderate DM pulsar (B1737+13) 4 x 50 MHz bands near 21 cm Investigate time variability of ScintArc structure and its effect on pulsar timing

49. B1737+13 secondary spectrum movie

50. 1133+16 dyn & sec D. Hemberger

51. 1133+16 dyn & sec D. Hemberger

52. Timing Residuals (Observed – Model) for PSR B1855+09

53. Summary Pulsars are ideal probes of the ionized ISM New phenomena to explore and learn to interpret Pulsars may detect gravitational waves before the expensive detectors! Larger more sensitive telescopes will provide breakthroughs! LOFAR, SKA... Thanks to: Sterrewacht Leiden & NWO

54. Scintillation Arcs Underlie Other Scintillation Patterns

55. Tilted 0355a Roger Foster, GB 140 ft

56. Tilted 0355b Roger Foster, GB 140 ft

57. Tilted 0919a

58. Tilted 0919b

59. The Gravitational Wave Spectrum R. N. Manchester (ATNF)

60. Sky Distribution of Millisecond Pulsars P < 20 ms and not in globular clusters R. N. Manchester (ATNF)

61. Black slide