UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B

Lopez, Laura A.; Castro, Daniel; Pearson, Sarah; Ramirez-Ruiz, Enrico; Yamaguchi, Hiroya; Slane, Patrick O.

doi:10.1088/0004-637X/777/2/145

Title: UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B

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Abstract

Recent observations have shown several supernova remnants (SNRs) have overionized plasmas, where ions are stripped of more electrons than they would be if in equilibrium with the electron temperature. Rapid electron cooling is necessary to produce this situation, yet the physical origin of that cooling remains uncertain. To assess the cooling scenario responsible for overionization, in this paper we identify and map the overionized plasma in the Galactic SNR W49B based on a 220 ks Chandra Advanced CCD Imaging Spectrometer observation. We performed a spatially resolved spectroscopic analysis, measuring the electron temperature by modeling the continuum and comparing it to the temperature given by the flux ratio of the He-like and H-like lines of sulfur and argon. Using these results, we find that W49B is overionized in the west, with a gradient of overionization increasing from east to west. As the ejecta expansion is impeded by molecular material in the east but not in the west, our overionization maps suggest the dominant cooling mechanism is adiabatic expansion of the hot plasma.

Authors:

Lopez, Laura A.; Castro, Daniel ^[1]; Pearson, Sarah ^[2]; Ramirez-Ruiz, Enrico ^[3]; Yamaguchi, Hiroya; Slane, Patrick O.

MIT-Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-664H, Cambridge, MA 02139 (United States)
Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen (Denmark)
Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95060 (United States)

Publication Date:: Sun Nov 10 00:00:00 EST 2013

OSTI Identifier:: 22270566

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 777; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ARGON IONS; ASTROPHYSICS; CHARGE-COUPLED DEVICES; COMPARATIVE EVALUATIONS; ELECTRON COOLING; ELECTRON TEMPERATURE; ELECTRONS; HOT PLASMA; PLASMA EXPANSION; SULFUR IONS; SUPERNOVA REMNANTS; SUPERNOVAE; X RADIATION

Citation Formats


                    Lopez, Laura A., Castro, Daniel, Pearson, Sarah, Ramirez-Ruiz, Enrico, Yamaguchi, Hiroya, Slane, Patrick O., and Smith, Randall K., E-mail: lopez@space.mit.edu. UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B.  United States: N. p., 2013. 
        Web.  doi:10.1088/0004-637X/777/2/145.

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                    Lopez, Laura A., Castro, Daniel, Pearson, Sarah, Ramirez-Ruiz, Enrico, Yamaguchi, Hiroya, Slane, Patrick O., & Smith, Randall K., E-mail: lopez@space.mit.edu. UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B.  United States.  https://doi.org/10.1088/0004-637X/777/2/145

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                    Lopez, Laura A., Castro, Daniel, Pearson, Sarah, Ramirez-Ruiz, Enrico, Yamaguchi, Hiroya, Slane, Patrick O., and Smith, Randall K., E-mail: lopez@space.mit.edu. 2013.  
        "UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B".  United States.  https://doi.org/10.1088/0004-637X/777/2/145.

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@article{osti_22270566,

  title        = {UNRAVELING THE ORIGIN OF OVERIONIZED PLASMA IN THE GALACTIC SUPERNOVA REMNANT W49B},

  author       = {Lopez, Laura A. and Castro, Daniel and Pearson, Sarah and Ramirez-Ruiz, Enrico and Yamaguchi, Hiroya and Slane, Patrick O. and Smith, Randall K., E-mail: lopez@space.mit.edu},

  abstractNote = {Recent observations have shown several supernova remnants (SNRs) have overionized plasmas, where ions are stripped of more electrons than they would be if in equilibrium with the electron temperature. Rapid electron cooling is necessary to produce this situation, yet the physical origin of that cooling remains uncertain. To assess the cooling scenario responsible for overionization, in this paper we identify and map the overionized plasma in the Galactic SNR W49B based on a 220 ks Chandra Advanced CCD Imaging Spectrometer observation. We performed a spatially resolved spectroscopic analysis, measuring the electron temperature by modeling the continuum and comparing it to the temperature given by the flux ratio of the He-like and H-like lines of sulfur and argon. Using these results, we find that W49B is overionized in the west, with a gradient of overionization increasing from east to west. As the ejecta expansion is impeded by molecular material in the east but not in the west, our overionization maps suggest the dominant cooling mechanism is adiabatic expansion of the hot plasma.},

  doi          = {10.1088/0004-637X/777/2/145},

  url          = {https://www.osti.gov/biblio/22270566},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 2,

  volume       = 777,

  place        = {United States},

  year         = {Sun Nov 10 00:00:00 EST 2013},

  month        = {Sun Nov 10 00:00:00 EST 2013}

}

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