HEAD 2000, November 2000
Session 42. Stars and Stellar Coronae
Display, Friday, November 10, 2000, 8:00am-6:00pm, Bora Bora Ballroom

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[42.22] Detection of Charge Exchange Emission From C/LINEAR 1999 S4

D. J. Christian (CSC/Space Telescope Science Institute), C. M. Lisse (Space Telescope Science Institute), K. Dennerl (Max-Planck-Institut fur extraterrestrische Physik), F. Marshall, R. F. Mushotsky, R. Petre, S. Snowden (NASA/GSFC), H. Weaver (Johns Hopkins University), B. Stoozas (University of California, Berkeley, CEA), S. Wolk (Chandra X-Ray Center, Harvard-Smithsonian CfA)

We present images, spectra, light curves, correlations with solar x-rays, and a comparison to models of cometary x-ray emission from our Chandra X-ray Observatory (CXO) and Extreme Ultraviolet Explorer (EUVE) observational campaign of Comet C/LINEAR 1999 S4. Our CXO observations spanned 2000 14 July 04:30 to 15 July 02:57 UT (pre-breakup, max signal) and 01 Aug to 02 Aug (post-breakup, min signal). The EUVE observations spanned from 2000 11 July 22:50 to 18 July 07:53 UT.

Pre-breakup, the comet was detected with a count rate in the ACIS S3 chip with 0.3 cps, a total integral flux of 8 x 10-13 erg/sec/cm2 from 0.2 - 0.7 keV, and a total x-ray luminosity of 6x1014 erg/sec. The emission morphology was found to be crescent shaped, similar to that found for previous comets, but with several discrete emission regions. Only a small segment of the EUVE data have been analyzed. The EUVE Lexan/B count rate at 04:57 July 14 UT was 0.06 cps in 5400 sec, for an equivalent luminosity of 1015 erg/sec at 0.16 keV. The ACIS-S spectrum shows the clear signatures of x-ray line emission due to charge exchange between cometary neutrals and solar wind minor ions; these include a strong line at 570 eV due to charge exchange to O6+, detected at greater than 10-sigma. Other lines are probably also present (e.g. N5+, N6+ at 300 - 500 eV), as the best fit to the preliminary spectrum is the Mewe et al. (MEKAL) multiple line emission spectrum using solar elemental abundances with enhanced oxygen and nitrogen abundances, and a plasma temperature of 0.17 keV.

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