Formation and dynamics of an electromagnetic bubble during the NS binary inspiral: theory and observational signatures

ORAL

Abstract

We consider a merging binary system of either two magnetized neutron stars or magnetars, or a neutron star -- black hole binary during the last year days of its evolution. Both compact companions possess magnetic moments and hence are sources of low-frequency electromagnetic (EM) waves, whose frequency is the inverse orbital period and, hence, does not exceed a few kHz. Such EM waves are evanescent: they do not propagate in ambient ISM plasmas because the wave frequency is below the plasma frequency. As the EM energy is continuously pumped into the system by the binary, there forms a cavity (or a bubble) filled with EM radiation. The bubble pushes on the surrounding plasma and can drive a shock wave through the ISM. The shock dynamics is different from the Sedov blast wave solution describing a freely expanding shock from a point-like explosion. Instead, the shock in the system at hand is continuously driven by the ever-increasing pressure inside the bubble. Here we explain the dynamics and evolution of the bubble and the driven shock. We predict that such shocks can be observed just before the merger. These sources become brighter and spectrally harder as the binary evolves toward the final merger. After the merger, the shock should ultimately settle onto the Sedov solution.

–

Authors

  • M.V. Medvedev

    U. Kansas

  • Jatinder Kumar

    Harvard U., Baker University, Bejing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Northrop Grumman, Baltimore, MD, University of Kansas Dept. of Physics \& Astronomy, Kansas State University, Department of Chemistry, College of Materials Science \& Engineering, Sichuan University, China, Illinois State University, Mullard Space Science Laboratory, University College of London, Holmbury St. Mary, United Kingdom, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, United States, Weizmann Institute of Science, Rehovot, Israel, Monmouth College, Missouri State University, Birla Institute of Technology and Science, University of Illinois at Urbana Champaign, Ames Laboratory. Department of Physics and Astronomy, Iowa State University, Siena College, \'Ecole Polytechnique F\'ed\'erale de Lausanne, Switzerland, Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Kansas State University, Purdue University, Princeton University, Oklahoma State University, University of Chicago, University of Iowa, University of Kansas, University of Kansas and University of Iowa