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Science 18 May 2001:
Vol. 292. no. 5520, pp. 1343 - 1348
DOI: 10.1126/science.292.5520.1343


Abstract
Full Text 		Charge Exchange-Induced X-Ray Emission from Comet C/1999 S4 (LINEAR)
C. M. Lisse, D. J. Christian, K. Dennerl, K. J. Meech, R. Petre, H. A. Weaver, S. J. Wolk

Supplementary Material

Supplemental Table 1. Model spectral fits to the CXO ACIS-S observations of C/LINEAR both pre-breakup (14 July 2000) and post-breakup (01 Aug 2000). Here, kT is the effective energy for the thermal bremsstrahlung continua in all models except for the power law models, where it is the index of the power-law. dof is the number of degrees of freedom of the fit, equivalent to the number of independent spectral channels in the Chandra observations. NH, the neutral hydrogen column density between Chandra and the comet, has been set to 1013 cm-2for the fits, as expected for the density of hydrogen in interplanetary space.
ModelkTtb(keV)Eline(keV)Eline(keV)Eline(keV)Eline(keV)c2/dofdofComments
2000 July 14
Power Law1.92 ± 0.0214.6104Index Free
Thermal Brem (TB)0.60 ± 0.0212.4104
TB + 4 lines0.41 ± 0.060.320.410.560.671.0382Line Centers, Widths Free
TB+ 6 Lines0.39 ± 0.020.320.400.49
0.60		0.56
0.67		0.9980Line Centers Free; Line Widths = Instrument Resolution
8 Lines...0.280.350.420.501.6175 No Continuum
0.570.610.670.75
2000 Aug 01
Power Law1.57 ± 0.051.8169Index Free
TB1.4 ± 0.21.6869
TB+ 3 Lines1.7 ± 0.50.320.410.56...0.9962Line Widths = Instrument Width

Supplemental Figure 1. (A) X-ray vs optical luminosity plot for the 15 detected EUVE/ROSAT comets and the Chandra/EUVE observations of C/LINEAR. Here Loptical is the comet's total 0.3 - 2.0 um scattered light emission, Lx is the total x-ray luminosity into 4p steradians, Afp is a measure of the comet's total dust production, and QH2O is a measure of the comet's total gas production (> 1/2 of a comet's emitted gas is water). The C/LINEAR S4 result falls near the maximum in the trend line for Lx. (B) Spatial extent of the emission versus the comet's outgassing rate. The observed extent for C/LINEAR is close to the predicted value, similar to the 105 km seen for other comets, and much larger than the expected bowshock position.


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Supplemental Figure 2. Spectral model fits to the emission : (A) thermal bremsstrahlung convolved with the ACIS-S instrument response, using best-fit kT = 0.60 keV ; (B) 4-line (variable width) model + thermal bremsstrahlung convolved with the ACIS-S instrument response (inset shows input model, as emitted by the comet); (C) same as (B), but using a 6-line instrumental width + thermal bremsstrahlung model (inset shows input model).


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