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.
  -----Model A----- -----Model B-----
  Param. Param. Param. P aram.
Parameter coupling value coupling value
C = $\rm 1.07 \times O$ =0.28 = $\rm 1.07 \times O$ 0.40
N = $\rm 3.14 \times O$ =0.82 = $\rm 3.14 \times O$ 1.18
O   0.26   0.37
Ne   3.15   3.97
S   =0.0   =0.0
Mg   =1.0   0.65
Si   =1.0   0.13
Fe   0.26   0.24
$\log{T_1}$   =6.3   =6.3
$\log{T_2}$   =6.5   =6.5
$\log{T_3}$   =7.3   =7.3
$\log{{\it EM}_1}$   52.64   52.53
$\log{{\it EM}_2}$ $2.35 \times {\it EM}_1$ =53.01 $2.35 \times {\it EM}_1$ =52.90
$\log{{\it EM}_3}$ $0.59 \times {\it EM}_1$ =52.41   52.53
$\chi^2_{\rm red}$ (d.o.f.) 2.79 (233) 2.61 (232)


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