Astronomy & Astrophysics

Table 1: Log of our XMM-Newton observations of $\gamma ^2$ Vel. For a definition of the phase see text of Sect. 2.
Table 2: Measured line fluxes (in 10^-13 erg cm^-2 s^-1) at Earth with 1 $\sigma$ errors in parenthesis.
Table 3: Fixed and fitted elemental abundances of the X-ray emitting material in $\gamma ^2$ Vel. The abundances are given relative to He in units of the solar ratio. The solar abundances are from Anders & Grevesse (1989), or from Grevesse & Sauval (1998, 1999) for Fe. Abundances given in italics were allowed to vary in the fit and the others were kept fixed.
Table 4: Best 4 component fit for combined XMM spectra of $\gamma ^2$ Vel at the two phases. Components 1 to 3 are collisionally ionized and component 4 is photo-ionized. $L_{\rm xi}$ is the unabsorbed X-ray luminosity in the range 0.4-10 keV for each component. 1 $\sigma$ uncertainties are given in parentheses. The Hipparcos distance to $\gamma ^2$ Vel of d = 258 pc is adopted. For comparison, a two-component fit to similar data for $\zeta$ Ori (O9.7Ib) is given.
Table 5: Best-fit model line fluxes at Earth in units of 10^-13 erg cm^-2 s^-1 for the high state ( upper section) and low state ( lower section) of $\gamma ^2$ Vel. A comparison with observations, and the relative contributions from the three CIE components (1, 2, 3) and the photo-ionized component (4) are also listed.