Astronomy & Astrophysics

Table 1: Observing log for the XMM-Newton observation of TW Hya on July 9, 2001. "Start'' and "Stop'' refer to start and end of exposures.
Table 2: Spectral lines identified in the first order XMM-Newton RGS spectrum of TW Hya. left - Observed line center, width, number of counts, and photon flux. Uncertainties include statistical 1 $\sigma$ error plus a systematic error stemming from the uncertainty of the local background level (see text for details). right - Line identifications from Mewe85.1, Mewe95.1, and Phillips99.1. For line blends we list the most likely contributors according to X-ray observations of other stars.
Table 3: Best fit parameters for the X-ray spectrum of TW Hya described by a multi-temperature thermal model (VMEKAL) including photo-absorption ( $N_{\rm H} = 2 \times 10^{20}~{\rm cm^{-2}}$ ). The electron density was fixed to $5 \times 10^{12}~{\rm cm^{-3}}$ . Elements not listed below are irrelevant in this spectrum, and their individual abundances were held fixed at the solar value. The temperatures and the coupling between some parameters were pre-determined by the analysis of the emission lines seen in the RGS spectrum. Values for the abundances are given with respect to the solar photosphere, $\log{T}$ is in K, and $\log{{\it EM}}$ in ${\rm cm^{-3}}$ . (A) - Best fit 3-T model to the EPIC MOS spectrum in the range $\lambda = 5{-}40$ Å. (B) - Same as (A) with free Mg and Si abundances.