detect brown dwarfs if they have an X-ray to bolometric flux ratio of $10^{-3}$.

The remaining 55 X-ray sources with no cluster counterpart are listed in Table \[nocounterparts\]. In an exposure of this length it is quite probable that many of these sources are extragalactic and there may also be a number of magnetically active field stars unassociated with the cluster. However, we have not listed possible correlations with the full optical catalogues of Naylor et al. (2002) and Jeffries et al. (2004) because the expected number of spurious correlations down to the limits of these catalogues (which would still have plausible X-ray-to-optical flux ratios for extragalactic sources) is of order 50 and many have several counterparts. These X-ray sources will not be discussed further in this paper.

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   No.           Name                RA           Dec       $\Delta$        ML                                       HR (pn)                                 
                                                arcsec                 (0.3-3.0)keV       (0.3-1.0)keV            (1.0-3.0)keV                               
   (1)            (2)               (3)           (4)         (5)          (6)                 (7)                     (8)                     (9)                  (10)
    3    XMMU J081012.9-491408   8 10 12.90   -49 14 08.6     1.22       2896.14      5.62E-02$\pm$2.33E-03   3.46E-02$\pm$1.84E-03   2.16E-02$\pm$1.43E-03   -0.231$\pm$0.040
    4    XMMU J080947.2-491305   8 09 47.25   -49 13 05.1     1.23       2607.62      5.40E-02$\pm$4.29E-03   4.15E-02$\pm$3.73E-03   1.25E-02$\pm$2.12E-03   -0.536$\pm$0.068
  ----- ----------------------- ------------ ------------- ---------- -------------- ----------------------- ----------------------- ----------------------- ------------------

  