D. Perrodin

West Virginia University, Morgantown, West Virginia, United States

Are you D. Perrodin?

Claim your profile

Publications (6)6.73 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We analyze timing noise from five years of Arecibo and Green Bank observations of the seventeen millisecond pulsars of the North-American Nanohertz Observatory for Gravitational Waves (NANOGrav) pulsar timing array. The weighted autocovariance of the timing residuals was computed for each pulsar and compared against two possible models for the underlying noise process. The first model includes red noise and predicts the autocovariance to be a decaying exponential as a function of time lag. The second model is Gaussian white noise whose autocovariance would be a delta function. We also perform a ``nearest-neighbor" correlation analysis. We find that the exponential process does not accurately describe the data. Two pulsars, J1643-1224 and J1910+1256, exhibit weak red noise, but the rest are well described as white noise. The overall lack of evidence for red noise implies that sensitivity to a (red) gravitational wave background signal is limited by statistical rather than systematic uncertainty. In all pulsars, the ratio of non-white noise to white noise is low, so that we can increase the cadence or integration times of our observations and still expect the root-mean-square of timing residual averages to decrease by the square-root of observation time, which is key to improving the sensitivity of the pulsar timing array.
    11/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present an analysis of high-precision pulsar timing data taken as part of the North American Nanohertz Observatory for Gravitational waves (NANOGrav) project. We have observed 17 pulsars for a span of roughly five years using the Green Bank and Arecibo radio telescopes. We analyze these data using standard pulsar timing models, with the addition of time-variable dispersion measure and frequency-variable pulse shape terms. Sub-microsecond timing residuals are obtained in nearly all cases, and the best root-mean-square timing residuals in this set are ~30-50 ns. We present methods for analyzing post-fit timing residuals for the presence of a gravitational wave signal with a specified spectral shape. These optimally take into account the timing fluctuation power removed by the model fit, and can be applied to either data from a single pulsar, or to a set of pulsars to detect a correlated signal. We apply these methods to our dataset to set an upper limit on the strength of the nHz-frequency stochastic supermassive black hole gravitational wave background of h_c (1 yr^-1) < 7x10^-15 (95%). This result is dominated by the timing of the two best pulsars in the set, PSRs J1713+0747 and J1909-3744.
    The Astrophysical Journal 01/2012; 762(2). · 6.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The NANOGrav collaboration seeks to detect gravitational waves from distant supermassive black hole sources using a pulsar timing array. In order to search for gravitational waves, it is necessary to have a good characterization of the timing noise for each pulsar of the pulsar timing array. Red noise is common in millisecond pulsars, and we need to quantify how much red noise is present for each pulsar. This can be done by looking at the power spectra of the pulsar timing residuals. However because the pulsar data are non-uniformly sampled, one cannot simply do a Fourier analysis. Also, commonly used least-square fitting methods such as the Lomb-Scargle analysis are not adequate for steep red spectra. Instead, we compute the power spectra of NANOGrav pulsar timing residuals using the Cholesky transformation, which eliminates spectral leakage. This is done with the help of the TEMPO2 ``SpectralModel" plugin developed by William Coles and George Hobbs.
    01/2012;
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is currently an international effort to detect gravitational waves using radio pulsar timing techniques. The detection will involve the analysis of signals observed from a large number of radio pulsars by many different observatories. We have developed an on-line web tool known as the International Pulsar Timing Array workBENCH (IPTA-BENCH) that will allow researchers to determine the effectiveness of different observing strategies for the detection of gravitational wave signals. This poster describes the current and future capabilities of IPTA-BENCH.
    01/2012;
  • D. Perrodin, A. Lommen
    [Show abstract] [Hide abstract]
    ABSTRACT: Astro 101 students have deep-seated pre-conceptions regarding such topics as the cause of moon phases or the seasons. Beyond exploring the topics in a learner-centered fashion, the "learning by teaching" philosophy enables students to truly master concepts. In order to make students teach the cause of moon phases, we created a multimedia project where groups of students taught other students and filmed the session. They were to produce a 10-minute final movie highlighting their teaching techniques and showing students in the process of learning the concepts. This "experiment" turned out to be a great success for a few reasons. First, students gained experience explaining conceptually-challenging topics, making them learn the material better. Additionally, they learned to apply learner-centered techniques, most likely learning to teach for the first time. Finally, this project provided the students a connection between the classroom and the rest of the college, making them responsible for applying and sharing their knowledge with their peers.
    09/2011;
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the spring of 2010, five undergraduates from Franklin & Marshall College conducted visits at J. P. McCaskey High School in Lancaster, Pennsylvania, under the umbrella of the Mid-Atlantic Relativistic Initiative in Education (MARIE). They introduced high school students to advanced topics in astronomy, such as dark matter, gravitational lensing, and cosmology. Not only did the outreach program benefit the high school students who were introduced to "sexy topics" in astronomy, but the undergraduates also gained teaching experience in a high school setting, learning to create lesson plans and to implement teaching techniques that engage students as active learners. They acted as role models for the high school students who were just a few years younger. They learned useful skills such as presenting information clearly and confidently, and with the use of journals they reflected on their teaching practice and shared reflections with the group throughout the semester, learning to become confident and reflective teachers.
    09/2011;