NANOGrav Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries in Circular Orbits

Arzoumanian, Z. and Brazier, A. and Burke-Spolaor, S. and Chamberlin, S. J. and Chatterjee, S. and Cordes, J. M. and Demorest, P. B. and Deng, X. and Dolch, T. and Ellis, J. A. and Ferdman, R. D. and Garver-Daniels, N. and Jenet, F. and Jones, G. and Kaspi, V. M. and Koop, M. and Lam, M. T. and Lazio, T. J. W. and Lommen, A. N. and Lorimer, D. R. and Luo, J. and Lynch, R. S. and Madison, D. R. and McLaughlin, M. A. and McWilliams, S. T. and Nice, D. J. and Palliyaguru, N. and Pennucci, Timothy Thomas and Ransom, S. M. and Sesana, A. (2014) NANOGrav Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries in Circular Orbits. ASTROPHYSICAL JOURNAL, 794 (2). ISSN 1538-4357

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Abstract

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project currently observes 43 pulsars using the Green Bank and Arecibo radio telescopes. In this work we use a subset of 17 pulsars timed for a span of roughly five years (2005–2010). We analyze these data using standard pulsar timing models, with the addition of time-variable dispersion measure and frequency-variable pulse shape terms. Within the timing data, we perform a search for continuous gravitational waves from individual supermassive black hole binaries in circular orbits using robust frequentist and Bayesian techniques. We find that there is no evidence for the presence of a detectable continuous gravitational wave; however, we can use these data to place the most constraining upper limits to date on the strength of such gravitational waves. Using the full 17 pulsar dataset we place a 95% upper limit on the sky-averaged strain amplitude of h0 . 3.8 × 10−14 at a frequency of 10 nHz. Furthermore, we place 95% all sky lower limits on the luminosity distance to such gravitational wave sources finding that the dL & 425 Mpc for sources at a frequency of 10 nHz and chirp mass 1010M . We find that for gravitational wave sources near our best timed pulsars in the sky, the sensitivity of the pulsar timing array is increased by a factor of ∼4 over the sky-averaged sensitivity. Finally we place limits on the coalescence rate of the most massive supermassive black hole binaries.

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