Computer Science
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006hrxs.confe..24n&link_type=abstract
High Resolution X-ray Spectroscopy: towards XEUS and Con-X, Proceedings of the international workshop held at the Mullard Space
Computer Science
Scientific paper
Classical T Tauri Stars (cTTS) are young stars still possessing an accretion disk. cTTS are found to produce strong X-ray emission and the origin of the observed X-rays can be attributed either to a dynamo-induced corona, the stars being very young and rotating very fast, or to an accretion shock. If the latter has a significant effect over the former, one expects to see different spectral signatures in high-resolution spectra of cTTS compared to stellar coronae without accretion disks. The most prominent and X-ray strongest cTTS is TW Hya, and Chandra HETGS observations showed that the He-like f/i-ratios are the lowest measured in all stellar coronae, suggesting an accretion shock as the origin of the observed X-ray emission. However, He-like triplets are affected by UV emission that can produce low f/i-ratios in the absence of any high densities. Schmitt & Ness (2005) presented an additional indicator for high densities, the ratio FeXVII λλ 17.10/17.05, which is, once more, the lowest among all stellar coronae. In this paper we present a careful examination of all measurements providing density diagnostics of cTTS in an effort to determine to what extent X-ray emission from an accretion shock influences the overall X-ray emission from cTTS. We conclude that progress can be made only with a lot more sensitive instruments with at least the same high spectral resolution as provided by Chandra and XMM-Newton gratings in order to assess a larger sample of suitable stars.
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