Table 2: Best-fit parameters for the EPIC spectra of the four sources in Table 1. Note that the fit to $\sigma $ Ori E refers to the global (quiescent+flare) spectrum. Errors are 90% confidence ranges for one interesting parameter.
  MOS1 MOS2 PN                  MOS1 MOS2 PN
  $\sigma $ Ori AB   $\sigma $ Ori E
T1 (keV) $\rm0.13_{-0.05}^{+0.07}$ $\rm0.13_{-0.05}^{+0.09}$ $\rm0.17_{-0.07}^{+0.31}$   $\rm0.75_{-0.20}^{+0.11}$ $\rm0.55_{-0.13}^{+0.23}$ $\rm0.41_{-0.04}^{+0.05}$
T2 (keV) $\rm0.35_{-0.02}^{+0.04}$ $\rm0.32_{-0.02}^{+0.02}$ $\rm0.33_{-0.02}^{+0.10}$   $\rm 2.96_{-0.31}^{+0.36}$ $\rm 3.83_{-0.84}^{+2.54}$ $\rm 3.24_{-0.20}^{+0.23}$
EM1 (1053 cm-3) $\rm 15.7_{-7.3}^{+5.9}$ $\rm 21.5_{-8.4}^{+7.1}$ $\rm 19.4_{-2.2}^{+27.1}$   $\rm 2.52_{-1.02}^{+2.15}$ $\rm 11.2_{-8.2}^{+11.8}$ $\rm 2.76_{-0.59}^{+0.81}$
EM2 (1053 cm-3) $\rm 18.7_{-10.2}^{+10.7}$ $\rm 41.8_{-13.0}^{+13.8}$ $\rm 39.9_{-23.8}^{+11.7}$   $\rm 14.5_{-2.4}^{+2.4}$ $\rm 16.2_{-4.6}^{+2.5}$ $\rm 15.9_{-1.3}^{+1.3}$
O $\rm0.76_{-0.33}^{+1.18}$ $\rm0.33_{-0.13}^{+0.23}$ $\rm0.34_{-0.10}^{+0.14}$   $\rm 1.56_{-0.84}^{+1.24}$ $\rm0.13_{-0.13}^{+0.48}$ $\rm0.75_{-0.26}^{+0.34}$
Ne $\rm0.99_{-0.38}^{+1.31}$ $\rm0.48_{-0.16}^{+0.28}$ $\rm0.51_{-0.11}^{+0.15}$   $\rm 2.11_{-1.15}^{+1.61}$ $\rm0.76_{-0.40}^{+1.42}$ $\rm 2.71_{-0.64}^{+0.80}$
Mg $\rm0.88_{-0.38}^{+1.24}$ $\rm0.53_{-0.21}^{+0.35}$ $\rm0.46_{-0.12}^{+0.17}$   $\rm0.21_{-0.21}^{+0.93}$ $\rm0.16_{-0.16}^{+0.54}$ $\rm 1.74_{-0.74}^{+0.90}$
Si $\rm 1.72_{-0.80}^{+2.37}$ $\rm 1.01_{-0.45}^{+0.73}$ $\rm0.84_{-0.26}^{+0.32}$   $\rm0.68_{-0.57}^{+0.76}$ $\rm0.24_{-0.24}^{+0.53}$ $\rm0.60_{-0.48}^{+0.55}$
S =1 =1 =1   $\rm0.10_{-0.10}^{+0.78}$ $\rm0.35_{-0.35}^{+1.07}$ $\rm0.00_{\dots}^{+0.50}$
Fe $\rm0.70_{-0.24}^{+0.87}$ $\rm0.39_{-0.13}^{+0.21}$ $\rm0.40_{-0.08}^{+0.10}$   $\rm0.36_{-0.18}^{+0.23}$ $\rm0.07_{-0.05}^{+0.24}$ $\rm0.44_{-0.12}^{+0.13}$
$\chi_r^2$/d.o.f. 1.78/55 1.50/56 1.15/174   0.54/97 0.87/104 0.67/288
Fx a (10-12 erg cm-2 s-1) 4.35 5.26 5.12   1.44 1.71 1.59
Lx a (1031 erg s-1) 6.45 7.80 7.59   2.14 2.54 2.36
  Source 3   Source 4
T1(keV) $\rm0.73_{-0.42}^{+0.10}$ $\rm0.76_{-0.17}^{+0.15}$ $\rm0.74_{-0.17}^{+0.08}$   $\rm0.46_{-0.09}^{+0.33}$ $\rm0.42_{-0.09}^{+0.25}$ $\rm0.48_{-0.08}^{+0.18}$
T2(keV) $\rm 2.07_{-0.35}^{+0.16}$ $\rm 2.58_{-0.55}^{+1.46}$ $\rm 2.29_{-0.44}^{+0.28}$   $\rm 2.86_{-0.63}^{+0.84}$ $\rm 2.29_{-0.37}^{+0.40}$ $\rm 2.55_{-0.23}^{+0.24}$
EM1(1053 cm-3) $\rm 3.68_{-1.44}^{+2.57}$ $\rm 7.00_{-3.74}^{+5.44}$ $\rm 4.54_{-1.09}^{+3.81}$   $\rm 1.71_{-1.05}^{+8.20}$ $\rm 3.63_{-1.27}^{+3.98}$ $\rm 1.51_{-0.43}^{+0.80}$
EM2(1053 cm-3) $\rm 9.21_{-1.36}^{+3.47}$ $\rm 6.61_{-1.41}^{+2.30}$ $\rm 7.49_{-1.56}^{+1.57}$   $\rm 5.65_{-1.71}^{+1.81}$ $\rm 8.72_{-1.53}^{+1.93}$ $\rm 6.79_{-0.87}^{+0.98}$
O $\rm0.58_{-0.51}^{+0.76}$ $\rm0.49_{-0.39}^{+0.84}$ $\rm0.54_{-0.36}^{+0.17}$   $\rm0.70_{-0.57}^{+1.09}$ $\rm0.14_{-0.14}^{+0.39}$ $\rm0.83_{-0.39}^{+0.73}$
Ne $\rm0.84_{-0.64}^{+0.81}$ $\rm0.96_{-0.53}^{+0.99}$ $\rm 1.26_{-0.55}^{+0.67}$   $\rm 2.41_{-1.50}^{+2.35}$ $\rm 1.10_{-0.58}^{+1.02}$ $\rm 2.55_{-0.85}^{+1.08}$
Mg =0.20 $\rm0.16_{-0.16}^{+0.50}$ $\rm0.23_{-0.23}^{+0.29}$   $\rm 1.27_{-1.01}^{+1.86}$ $\rm0.40_{-0.40}^{+0.72}$ $\rm0.68_{-0.61}^{+0.79}$
Si $\rm0.09_{-0.09}^{+0.31}$ $\rm0.35_{-0.29}^{+0.49}$ $\rm0.06_{-0.06}^{+0.21}$   $\rm 1.56_{-1.08}^{+1.54}$ $\rm0.53_{-0.50}^{+0.57}$ $\rm0.14_{-0.14}^{+0.47}$
S $\rm0.30_{-0.30}^{+0.36}$ $\rm0.87_{-0.67}^{+0.89}$ $\rm0.18_{-0.18}^{+0.37}$   $\rm0.80_{-0.80}^{+1.50}$ $\rm0.00_{\dots}^{+0.31}$ $\rm0.00_{\dots}^{+0.42}$
Fe $\rm0.17_{-0.11}^{+0.10}$ $\rm0.09_{-0.05}^{+0.14}$ $\rm0.15_{-0.08}^{+0.10}$   $\rm0.28_{-0.20}^{+0.33}$ $\rm0.10_{-0.07}^{+0.14}$ $\rm0.34_{-0.14}^{+0.16}$
$\chi_r^2$/d.o.f. 0.69/69 0.55/57 0.64/202   0.61/55 0.73/61 0.62/191
Fx a (10-13 erg cm-2 s-1) 9.64 9.60 8.83   6.20 7.86 7.06
Lx a (1031 erg s-1) 1.43 1.42 1.31   0.92 1.17 1.05
a Unabsorbed flux and luminosity in the ROSAT (0.1-2.4 keV) band. Lx has been computed assuming d=352 pc for all sources. Note that the luminosity of $\sigma $ Ori E might be higher by a factor of 3.3 if its distance is 640 pc, see Sect. 4.2.

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