\begin{table}%T7
\caption{Main characteristics of the X-ray sources with no candidate optical counterpart and $\log(f_{\rm X}/f_{\rm opt})\protect \ga 2$.}\label{candidates}
\small%\centerline
{
\begin{tabular}{cccccccc}
 \hline\hline
(1)	&	(2)			&	(3)				&	(4)		&	(5)		&	(6)		&	(7)		&	(8)		\\
OBS	&	SRC			&	DETECTION BANDS			&	$kT_{\rm br}$	&	$kT_{\rm bb}$	&	$\Gamma$	&	Flux		& 	$f_{\rm X}/f_{\rm opt}$	\\
	&				&	(keV)				&	(keV)		&	(keV)		&			& (10$^{-14}$ cgs)	& 	(log)		\\ 
	\hline
2	&	XMMU J061807.6-331237	&	0.5--1 				&	$\le$5		&	0.2		&	$\ge$1	&	2.28	$\pm$ 1.23	&	1.73	$\pm$ 0.31	\\ \hline
3	&	XMMU J061429.8-333225	&	0.5--2; 0.5--1; 1--2 		&	$\ge$2		&	0.5		&	1--2.5	&	12.92	$\pm$ 3.67	&	2.48	$\pm$ 0.24	\\
3	&	XMMU J061450.2-331501	&	0.5--2; 1--2 			&	2--5		&	$>$0.2		&	1.5--2	&	5.14	$\pm$ 2.21	&	2.08	$\pm $ 0.27	\\
3	&	XMMU J061526.1-331724	&	0.5--2; 1--2 			&	$\ge$2		&	$>$0.2		&	1--2	&	3.22	$\pm$ 1.12	&	1.88	$\pm$ 0.25	\\
3	&	XMMU J061546.9-333347	&	1--2 				&	$\ge$1		&	$\ge$0.2	&	$\le$2.5	&	1.93	$\pm$1.03	&	1.66	$\pm$ 0.31	\\ 
\hline
4	&	XMMU J061507.9-330026	&	0.5--2; 2--10; 1--2; 2--4.5		&	$>$5		&	$>$0.5		&	$\le$1	&	3.67	$\pm$ 1.18	&	1.93	$\pm$ 0.24	\\
4	&	XMMU J061557.2-324635	&	0.5--2; 1--2 			&	0.5--5		&	0.2--0.5	&	2--2.5	&	2.95	$\pm$ 1.47	&	1.84	$\pm$ 0.29	\\
4	&	XMMU J061504.5-330533	&	0.5--2 				&	$\le$5		&	$>$0.2	&	$\ge$1.5	&	2.06	$\pm$	1.41	&	1.68	$\pm$ 0.36	\\ 
\hline
8	&	XMMU J124642.5-832212	&	2--10 				&	$>$5		&	$>$0.5		&	$<$1	&	3.62	$\pm$ 1.69	&	1.77	$\pm$ 0.20	\\ \hline
\end{tabular}}
\smallskip
Key to Table -- Col.~(1):  {\it  EPIC} field sequential reference number.
Column~(2):  Source identification.   Column~(3): Source  Detection Bands,
i.e.   the energy  ranges $j$  where the  probability $P(j)$  that the
source counts  are due  to a background  fluctuation is lower  than $2
\times  10^{-4}$ (see text).   Column~(4):  Estimated range  of possible
$kT_{\rm br}$   temperatures  for   a   thermal  bremsstrahlung   spectrum
(i.e. XSPEC {\it wabs bremss} model) compatible with the measured {\it 
HRs}.  Col.  (5): Estimated  range of possible  $kT_{\rm bb}$ temperatures
for a thermal  blackbody spectrum (i.e. XSPEC {\it  wabs bbody} model)
compatible with the measured {\it   HRs}.  Column~(6): Estimated range of
photon index $\Gamma$ values for a power law spectrum (i.e. XSPEC {\it
wabs pow} model) compatible with the measured {\it  HRs}. In all cases,
we  assumed  the  galactic  $N_{\rm  H}$  estimated  in  the  pointing
direction  (Table~\ref{observations}).  The wide  range of  values for
the spectral  parameters $kT_{\rm  br}$, $kT_{\rm  bb}$ and $\Gamma$  are due to
the low  count statistics and to  the large error bars  on the derived
source {\it  HRs}.  Column~(7): Estimated source flux in the energy range
0.3$-$10~keV, assuming a power law spectrum with $\Gamma = 1.7$ and the
galactic $N_{\rm H}$ in the pointing direction.  Column~(8): Lower limit
(in logarithmic units) of  the X-ray-to-optical ratio, assuming the
X-ray flux of Col.~(6) and the derived optical flux upper limits.
\end{table}