The Extreme Dimension: Time-Variability and The Smallest ISM Scales

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 linear grayscale logarithmic grayscale

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

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

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

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

17. Cumulative Delay - Arclets

18. Kolmogorov: time delays scale as

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 incident plane wave () V y D Conjugate time axis (heuristic) d

23. conjugate freq axis D Conjugate frequency axis (heuristic) 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. where do the arclets come from ?” 1d “image” on the sky Walker et al. 2004 Where do the “arclets” (inverted parabolas) come from?

27. Some ObservationalHighlights ...

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 fn = h ft2

33. PSR 1133+16 s=0 s=1 proper motion (2d) fn = h ft2

36. Can We Improve High-accuracyPulsar Timing?

37. Detection of Gravitational Waves (NASA GSFC) • Prediction of general relativity and other theories of gravity • Generated by acceleration of massive object(s) • 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 R. N. Manchester (ATNF) (K. Thorne, T. Carnahan, LISA Gallery)

38. Timing residuals for PSR B1855+09 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. 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. Dan Stinebring Oberlin College dan.stinebring@oberlin.edu 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!!

43. Detection of Gravitational Waves (NASA GSFC) • Prediction of general relativity and other theories of gravity • Generated by acceleration of massive object(s) • 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 R. N. Manchester (ATNF) (K. Thorne, T. Carnahan, LISA Gallery)

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 Want to achieve < 1 us residuals for 10 pulsars for 5 years Timing residuals for PSR B1855+09 R. N. Manchester (ATNF)

45. R. N. Manchester Sept 2006

46. data: R. N. Manchester

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

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 spectrummovie

50. 1133+16 dyn & sec D. Hemberger