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S.P. Reynolds, K.J. Borkowski, B.J. Williams (NC State U.), W.P. Blair, P. Ghavamian, R. Sankrit (JHU), S.P. Hendrick (Millersville U.), K.S. Long (STScI), J.A. Morse (ASU), J.C. Raymond (CfA), R.C. Smith, S. Points (CTIO), P.F. Winkler (Middlebury)
We present Spitzer Space Telescope imaging and spectroscopic observations of the combination shell/pulsar-wind nebula (PWN) supernova remnant 0540-693 in the Large Magellanic Cloud. The broadband images show the PWN clearly; measured fluxes at 24 \mum (MIPS) and between 3.6 and 8 \mum (IRAC) fall precisely on simple power-law extrapolations up from radio frequencies and down from optical frequencies, respectively. Emission from the shell cannot be clearly separated from extensive surrounding emission. For the PWN, a spectral break from the radio power-law index value of --0.3 to the optical index of --1.1 occurs fairly suddenly between the MIPS and IRAC wavelengths. Our IRS spectrum covers this break, and also shows spectral lines of [Ar II], [Ar III], [Ne II], [Ne III], [S III], [S IV], [Fe II], and [FeIII]. The brighter lines show clear, asymmetric Doppler broadening. We discuss the consequences of these results for the understanding of the PWN of 0540-693. We also present global spectral models for PWNe with energy-loss breaks and describe the physical requirements that the break observed for 0540-693 could be due to synchrotron losses.
We acknowledge support from NASA for this work.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.