Spatial identification of the overionized plasma in W49B
Abstract
Recent Suzaku X-ray observations of the ejecta-dominated supernova remnant W49B have shown that in the global spectrum there is a clear indication for the presence of overionized plasma whose physical origin is still under debate. In order to ascertain the physical origin of such a rapidly cooling plasma, we focus on the study of its spatial localization within the X-ray emitting ejecta. We confirm the presence of a saw-edged excess (interpreted as a strong radiative recombination continuum) in the global spectrum above 8 keV, emerging above the ionization-equilibrium model. We produce a hardness ratio map to determine where the plasma is overionized and we perform a spectral analysis of the regions with and without strong overionization. We find that the overionized plasma is localized in the center of the remnant and in its western jet, while it is not detected in the bright eastern jet, where the expansion of the ejecta is hampered by their interaction with a dense interstellar cloud. The location of overionized plasma suggests that the inner ejecta are rapidly cooling by expansion, unlike the outer ejecta, for which expansion is hampered by interstellar clouds seen in H2
Keywords
Cite
@article{arxiv.1004.1604,
title = {Spatial identification of the overionized plasma in W49B},
author = {M. Miceli and F. Bocchino and A. Decourchelle and J. Ballet and F. Reale},
journal= {arXiv preprint arXiv:1004.1604},
year = {2015}
}
Comments
Accepted for publication as a Letter in Astronomy and Astrophysics.