Emission lines between 1 and 2 keV in Cometary X-ray Spectra. (arXiv:1212.0624v1 [astro-ph.EP])

Emission lines between 1 and 2 keV in Cometary X-ray Spectra. (arXiv:1212.0624v1 [astro-ph.EP]):
We present the detection of new cometary X-ray emission lines in the 1.0 to
2.0 keV range using a sample of comets observed with the Chandra X-ray
observatory and ACIS spectrometer. We have selected 5 comets from the Chandra
sample with good signal-to-noise spectra. The surveyed comets are: C/1999 S4
(LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003
(Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended
version of our solar wind charge exchange (SWCX) emission model (Bodewits et
al. 2007). Above 1 keV, we find Ikeya-Zhang to have strong emission lines at
1340 and 1850 eV that we identify as being created by solar wind charge
exchange lines of Mg XI and Si XIII, respectively, and weaker emission lines at
1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV,
respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a
significant level for the other comets in our sample (LS4, MH, Encke, 8P), and
these lines promise additional diagnostics to be included in SWCX models. The
silicon lines in the 1700 to 2000 eV range are detected for all comets, but
with the rising background and decreasing cometary emission, we caution these
detections need further confirmation with higher resolution instruments.