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Low Frequency Observations of the ISM and Pulsar Timing

Low Frequency Observations of the ISM and Pulsar Timing. Joris Verbiest. Swinburne University & ATNF, Australia. Xiaopeng You (Southwest University, China) William Coles (UCSD) George Hobbs (ATNF) PPTA team. Outline. Brief intro to PPTA DM variations and the turbulent ISM

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Low Frequency Observations of the ISM and Pulsar Timing

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  1. Low Frequency Observations of the ISM and Pulsar Timing Joris Verbiest Swinburne University & ATNF, Australia Xiaopeng You (Southwest University, China) William Coles (UCSD) George Hobbs (ATNF) PPTA team

  2. Outline • Brief intro to PPTA • DM variations and the turbulent ISM • PSR J0437-4715’s DM Structure Function • TOA-intensity correlation • Summary

  3. PPTA Team Members • Australia Telescope National Facility, CSIRO, Sydney Dick Manchester, George Hobbs, David Champion, John Sarkissian, John Reynolds, Mike Kesteven, Warwick Wilson, Grant Hampson, Andrew Brown, David Smith, Jonathan Khoo, (Russell Edwards) • Swinburne University of Technology, Melbourne Matthew Bailes, Willem van Straten, Joris Verbiest, Ramesh Bhat, Sarah Burke, Andrew Jameson • University of Texas, Brownsville Rick Jenet • University of California, San Diego Bill Coles • Franklin & Marshall College, Lancaster PA Andrea Lommen • University of Sydney, Sydney Daniel Yardley • National Observatories of China, Beijing Johnny Wen • Peking University, Beijing Kejia Lee • Southwest University, Chongqing Xiaopeng You • Curtin University, Perth Aidan Hotan

  4. Pulsar Timing Arrays • Main goal: Detect gravitational waves • Secondary goals: Investigate time standards Investigate Solar System Investigate ISM …

  5. DM Variations in Timing 50cm 20cm 10cm 20cm

  6. PPTA DM Variations You et al., MNRAS, 2007

  7. DM Structure Function • Measure of turbulent power at different scales • Expected to be exponential with spectral index α = 5/3 for Kolmogorov model

  8. Typical SF You et al., MNRAS, 2007

  9. (1000 days ≈ 7.8 AU) Kolmogorov Slope You et al., MNRAS, 2007

  10. Large Inner Scale You et al., MNRAS, 2007 (10 days ≈ 0.4 AU)

  11. PSR J0437-4715 SF You et al., MNRAS, 2007 1000 days ≈ 61 AU

  12. 0437 DM Variations ~500 days ≈ 30 AU 2004 2008

  13. Scintillation & TOAs • PSR J0437-4715 • 685 MHz • 2 hours, 8sec integrations TOA residual Signal-to-Noise-1

  14. Scintillation/TOA - Simulations Coles et al., in preparation

  15. Grad DM - Simulations Coles et al., in preparation

  16. Correlation - Real Data Coles et al., in preparation

  17. Conclusions PTAs need high timing precision.  ISM effects need to be corrected  Most easily measured at low frequencies  ISM: an interesting place that keeps surprising…

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