Dispersion Measure Variations in the NANOGrav Nine-Year Data Set

ORAL

Abstract

The North American Nanohertz Observatory for Gravitational waves (NANOGrav) is a collaboration of scientists working to detect gravitational waves using pulsar timing. Dispersion, a frequency-dependent time delay caused by free electrons along the line of sight, needs to be corrected for in the pulsar data in order to achieve the necessary sensitivity required to detect gravitational radiation. We analyze the dispersion measure (DM) variations of 37 milliseconds pulsars in the nine-year NANOGrav data release and constrain the sources of these variations. Variations in the DM over time can be caused by a variety of factors, including an increasing or decreasing distance between the pulsar and the Earth, inhomogeneities in the ISM, and solar effects. We fit for these types of trends in the DM measurements with time to measure the scale and periodicity, if any, of the variations. We present the structure functions of these pulsars and compare them to that expected for a Kolmogorov medium.

–

Authors

  • Megan Jones

    West Virginia University

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division