Low Frequency Observations of the ISM and Pulsar Timing
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Low Frequency Observations of the ISM
and Pulsar Timing
Joris Verbiest
Xiaopeng You (Southwest University, China)
William Coles (UCSD)
George Hobbs (ATNF)
PPTA team
Swinburne University & ATNF, Australia
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Outline
• Brief intro to PPTA
• DM variations
and the turbulent ISM
• PSR J0437-4715’s
DM Structure Function
• TOA-intensity correlation
• Summary
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Australia Telescope National Facility, CSIRO, SydneyDick 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, MelbourneMatthew Bailes, Willem van Straten, Joris Verbiest, Ramesh Bhat, Sarah Burke, Andrew Jameson
University of Texas, BrownsvilleRick Jenet
University of California, San DiegoBill Coles
Franklin & Marshall College, Lancaster PAAndrea Lommen
University of Sydney, SydneyDaniel Yardley
National Observatories of China, BeijingJohnny Wen
Peking University, BeijingKejia Lee
Southwest University, ChongqingXiaopeng You
Curtin University, PerthAidan Hotan
PPTA Team Members
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Pulsar Timing Arrays
• Main goal: Detect gravitational waves
• Secondary goals:Investigate time standardsInvestigate Solar SystemInvestigate ISM…
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DM Variations in Timing
50cm
20cm
10cm
20cm
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PPTA DM VariationsYou et al.,
MNRAS, 2007
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DM Structure Function
• Measure of turbulent power at different scales
• Expected to be exponential with spectral index α = 5/3 for Kolmogorov model
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Typical SF
You
et
al.,
MN
RA
S,
20
07
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Kolmogorov Slope
(1000 days ≈ 7.8 AU) You
et
al.,
MN
RA
S,
200
7
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Large Inner Scale
(10 days ≈ 0.4 AU) You
et
al.,
MN
RA
S,
20
07
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PSR J0437-4715 SF
1000 days ≈ 61 AU
You et al., MNRAS, 2007
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0437 DM Variations
~500 days ≈ 30 AU
2004 2008
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Scintillation & TOAs• PSR J0437-4715
• 685 MHz
• 2 hours, 8sec integrations
TOA residual Signal-to-Noise-1
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Scintillation/TOA - Simulations
Cole
s et
al.,
in p
repara
tion
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Grad DM - Simulations
Coles et al., in preparation
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Correlation - Real Data
Cole
s et
al.,
in p
repara
tion
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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…