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Highlights

Here we present some of the achievements of the PPTA projects.

Major scientific goals:

  • Characterising the nanohertz gravitational-wave universe:
    • Detecting and limiting the gravitational-wave background: Yardley et al. (2011) used the PPTA data sets to attempt to detect a gravitational wave background. Unfortunately no gravitational waves were found. Jenet et al. (2006) provided the first stringent upper bound on the gravitational wave background using the PPTA data sets. Shannon et al. (2013) presented a revised upper limit on the gravitational-wave background demonstrating the sensitivity of the PPTA datasets.
    • Single sources: Yardley et al. (2010) presented the first analysis of the sensitivity of an actual PTA to individual, continuous-wave sources of gravitational waves
    • Predicting GW signals: We have used the millennium simulations and accompanying semi-analytic models to predict the strength and non-Gaussianity of the gravitational wave background from massive black hole binaries (Ravi et al. 2012).
  • Improving the solar system ephemeris:
    • Combining PPTA data with other timing data sets, Champion et al. (2010) published the most precise estimate for the mass of the Jovian system.
  • Improving terrestrial time standards:
    • We have used the PPTA observations to develop the first major pulsar-based timescale (Hobbs et al. 2012).

Data sets:

  • Our first major data release was competed in 2012 and is presented as part of the PPTA overview paper (Manchester et al. 2013).
  • In collaboration with CSIRO IM&T and the Australia National Data Service, we have developed a data archive of pulsar observations from the Parkes telescope.
  • Verbiest et al. (2009) performed the first large-scale analysis of timing stability of millisecond pulsars, demonstrating the practical feasibility of a PTA detection of a gravitational-wave background.

Algorithms:

  • A new algorithm for correcting for dispersion measure variations (Keith et al. 2013).
  • Methodology for correcting for red noise in pulsar timing datasets (Coles et al. 2011).
  • Techniques for high-fidelity polarimety (van Straten 2013).
  • Jenet et al. (2005) described, for the first time, the number of pulsars, observation duration and timing precision required to detect the expected gravitational wave background.

Instrumentation and software development

  • Development of Tempo2:
    • Hobbs et al. (2006) and Edwards et al. (2006) described the new software package, tempo2, that had been developed for the PPTA project.
    • Hobbs et al. (2009) demonstrated how gravitational wave signals (individual sources or a background) can be simulated within the tempo2 software package.
    • We have continued to develop tempo2 with a variety of fitting methods and plugins to analyse arrival times.
  • Instrumentation:
    • We have developed a number of digital filterbank systems(PDFB1,2,3,4) and coherent dedispersion machines (APSR, CASPSR) that have been deployed at the Parkes Telescope.
    • Kesteven et al. (2005) developed a method for removing radio frequency interference from pulsar data sets using an adaptive filter algorithm.
    • We have developed techniques to make absolute time of arrival measurements.

Education and Public outreach:

  • We have deveoped the PULSE@Parkes that allows high school students to take part in the data acquisition for the PPTA project.
  • We organised the third IPTA School attended by 45 students (undergraduate to postdoctoral level) from Africa, Asia, Australia, Europe, and North America. The school was held in 2012 at the University of Sydney.
  • We organised the sixth IPTA Schooled attended by 30 students (undergraduate to postdoctoral level) from Africa, Asia, Australia, Europe, and North America. The school was held in 2015 at the Parkes Observatory.

Ancillary Science:

  • Pulse shape changes: Oslowski et al. (2011) studied PSR J0437-4715 in depth and discussed the fundamental limits of pulsar timing precision. Shannon et al. (2014) demonstrated that pulse shape variations contribute additional timing uncertainty in a number of pulsars.
  • Interstellar and interplanetary media: You et al. (2007b) used the PPTA data sets to study the interstellar medium through variations in the pulsar dispersion measures. You et al. (2007a, 2012) used the PPTA data sets to study the Solar wind. Yan et al. (2012) searched for rotation measure variations along the lines of sight to the PPTA pulsars.
  • Polarimetry of millisecond pulsars. Yan et al (2011) used the PPTA datasets to study the polarisation of millisecond pulsars in the 20cm band. Dai et al (2015) presented a multiwavelength study of the polarisation and pulse-profile evolution of the PPTA pulsars.