تقرير
Physical Conditions of Accreting Gas in T Tauri Star Systems
| العنوان: | Physical Conditions of Accreting Gas in T Tauri Star Systems |
|---|---|
| المؤلفون: | Bary, Jeffrey S., Matt, Sean P., Skrutskie, Michael F., Wilson, John C., Peterson, Dawn E., Nelson, Matthew J. |
| سنة النشر: | 2008 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics |
| الوصف: | We present results from a low resolution (R~300) near-infrared spectroscopic variability survey of actively accreting T Tauri stars (TTS) in the Taurus-Auriga star forming region. Paschen and Brackett series H I recombination lines were detected in 73 spectra of 15 classical T Tauri systems. The values of the Pan/PaB, Brn/BrG, and BrG/Pan H I line ratios for all observations exhibit a scatter of < 20% about the weighted mean, not only from source to source, but also for epoch-to-epoch variations in the same source. A representative or `global' value was determined for each ratio in both the Paschen and Brackett series as well as the BrG/Pan line ratios. A comparison of observed line ratio values was made to those predicted by the temperature and electron density dependent models of Case B hydrogen recombination line theory. The measured line ratios are statistically well-fit by a tightly constrained range of temperatures (T < 2000 K) and electron densities 1e9 < n_e < 1e10 cm^-3. A comparison of the observed line ratio values to the values predicted by the optically thick and thin local thermodynamic equilibrium cases rules out these conditions for the emitting H I gas. Therefore, the emission is consistent with having an origin in a non-LTE recombining gas. While the range of electron densities is consistent with the gas densities predicted by existing magnetospheric accretion models, the temperature range constrained by the Case B comparison is considerably lower than that expected for accreting gas. The cooler gas temperatures will require a non-thermal excitation process (e.g., coronal/accretion-related X-rays and UV photons) to power the observed line emission. Comment: 12 pages, emulateapj format, Accepted for publication in ApJ |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1086/591487 |
| URL الوصول: | http://arxiv.org/abs/0807.1727 |
| رقم الأكسشن: | edsarx.0807.1727 |
| قاعدة البيانات: | arXiv |
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