%0 Journal Article
%T Hot Gas Lines in T Tauri Stars
%A David R. Ardila
%A Gregory J. Herczeg
%A Scott G. Gregory
%A Laura Ingleby
%A Kevin France
%A Alexander Brown
%A Suzan Edwards
%A Christopher Johns-Krull
%A Jeffrey L. Linsky
%A Hao Yang
%A Jeff A. Valenti
%A Herv¨¦ Abgrall
%A Richard D. Alexander
%A Edwin Bergin
%A Thomas Bethell
%A Joanna M. Brown
%A Nuria Calvet
%A Catherine Espaillat
%A Lynne A. Hillenbrand
%A Gaitee Hussain
%A Evelyne Roueff
%A Eric R Schindhelm
%A Frederick M. Walter
%J Physics
%D 2013
%I arXiv
%R 10.1088/0067-0049/207/1/1
%X For Classical T Tauri Stars (CTTSs), the resonance lines of N V, Si IV, and C IV, as well as the He II 1640 A line, act as diagnostics of the accretion process. Here we assemble a large high-resolution dataset of these lines in CTTSs and Weak T Tauri Stars (WTTSs). We present data for 35 stars: one Herbig Ae star, 28 CTTSs, and 6 WTTSs. We decompose the C IV and He II lines into broad and narrow Gaussian components (BC & NC). The most common (50 %) C IV line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. The velocity centroids of the BCs and NCs are such that V_BC > 4 * V_NC, consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He II CTTSs lines are generally symmetric and narrow, less redshifted than the CTTSs C IV lines, by ~10 km/sec. The flux in the BC of the He II line is small compared to that of the C IV line, consistent with models of the pre-shock column emission. The observations are consistent with the presence of multiple accretion columns with different densities or with accretion models that predict a slow-moving, low-density region in the periphery of the accretion column. For HN Tau A and RW Aur A, most of the C IV line is blueshifted suggesting that the C IV emission is produced by shocks within outflow jets. In our sample, the Herbig Ae star DX Cha is the only object for which we find a P-Cygni profile in the C IV line, which argues for the presence of a hot (10^5 K) wind. For the overall sample, the Si IV and N V line luminosities are correlated with the C IV line luminosities, although the relationship between Si IV and C IV shows large scatter about a linear relationship and suggests that TW Hya, V4046 Sgr, AA Tau, DF Tau, GM Aur, and V1190 Sco are silicon-poor.
%U http://arxiv.org/abs/1304.3746v1