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T. J. Gaetz (Harvard-Smithsonian CfA), P. Ghavamian, R. Sankrit (Johns Hopkins University), M. Sasaki, P. P. Plucinsky (Harvard-Smithsonian CfA), R. K. Smith (GSFC/Johns Hopkins University), R. C. Raymond (Harvard-Smithsonian CfA), W. P. Blair (Johns Hopkins University)
In the Northeastern Cygnus Loop, 180-350 km/s shocks are propagating into low density (n ~ 1 cm-3), partially neutral material. Radiative cooling in these shocks is negligible (they are nonradiative), and their optical spectra are dominated by collisionally excited Balmer-line emission. The shapes of these Balmer lines provide a constraint on the shock velocity and the degree of electron-ion temperature equilibration at the shock front. We have imaged some of these shocks with the Chandra X-ray Observatory. The softness of the emission makes the analysis sensitive to the low energy calibration. We present analyses making use of the recent improvements in understanding this low energy response, and particularly the spatially dependent absorption by the contamination layer on the ACIS optical blocking filter. The the O VII, O VIII, and Ne IX X-ray line emission systematically varies with distance behind the shock, allowing comparison with the predictions of shock models, and also with existing FUSE observations of O VI variation behind these shocks.
This work was supported by NASA grants G02-3092A and NAG5-9978, and by NASA contract NAS8-03060.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.