\begin{table}%t2
 \caption{Integrated strength of the PAH emission features.\label{tab_obs_2}}
%\centerline
{\begin{tabular}{lllllllll}
\hline
\hline
Object & 3.3       & 6.2    & "7.7'' & 8.6 & 11.2(3) & 12.7 & 16.4 & Ref.\\
       & $[\mu \rm m]$ & $[\mu \rm m]$ & $[\mu\rm  m]$ & $[\mu\rm  m]$ & $[\mu\rm  m]$ & $[\mu\rm  m]$ & $[\mu\rm  m]$ \\
\hline
AB Aur    &  $<$1$^a$   & 4.4(0.3)   & 4.2(0.6) & 2(0.2)   &  2(0.6) &-- &-- & (1)\\%& 0.23 & 1 & 2\\  
HD 100546 &  2.5(0.5)  & 14.3(0.4)  & 19.2(0.8)  & 4.6(0.5)   & --$^b$&-- &--  & (1) \\%& 0.18 & 0.74 & --\\  
HD 142527 &  1(0.6)   &$<$1.5    &  --  & --&  $<$0.5&-- &-- & (1) \\%&$>$1.4 & -- &--\\  
HD 179218 &  1.7(0.2)  &8.1(0.4)    &14.4(0.6) & 1.6(0.4)   & -- &-- &--  & (1)       \\%& 0.2 & 0.56 & 
HD 100453 &  1.3(0.2)  & 2.6(0.5)   &--&--    & 1.2(0.3)&-- &--  & (1)\\%& 0.5 & -- &-- \\  
HD 135344 &  $<$0.5         & $<$1.5         & ?& -- & $<$1&-- &-- & (2)\\
HD 139614 &  $<$0.5         &$<$1.5          & -- &-- & $<$0.5&-- &-- & (2)\\
HD 169142 &  1(0.2)   & 2.8(0.3)   &  -- &-- &  2.3(0.5)&-- &-- & (1) \\%& 0.36 & -- &--\\  
HD 104237&  $<$0.5         & $<$1.5          & -- &-- & --&-- &-- & (2)\\
HD 142666 &   0.3(0.2)  & 2.6(0.3)   & -- &--  & -- &-- &-- & (1)  \\%& 0.11&--&--\\  
HD 144432&  $<$0.5         & $<$1.5          & -- &-- & --&-- &-- & (2)\\
HD 150193 & $<0.08$$^a$    & $<$1.5          & -- &-- & --&-- &-- & (2)\\
HD 163296 &$<$0.2$^a$    &  $<$1.5   &  --    &   --  &  --  &-- &-- & (2)  \\
\hline
HD 97048  &    1.3(0.3) &  6.9(0.8)  & 11.8(1.3) & 2.4(0.6)  &  3.4(0.4)& 1(0.2) &-- & (2)  \\%& 0.19 &0.6 & 3.5\\  
Elias 1   &   0.5$^c$(0.1)  & 6.1(0.6)   &  9.4(0.1)  & 2.3(0.1) & --$^d$ &-- &-- & (2)   \\%& 0.1 & 0.65 & -\\ 
\hline
Lk H$\alpha$ 25 & 0.076(0.006)   &           &  & &&&& (3) \\ 
HK Ori          &0.087(0.045)   &           &  & &&&& (3) \\ 
HD 245185       &0.035(0.018)  &           &  & &&&& (3) \\ 
Lk H$\alpha$ 198& $<$0.15 &           &  & & &&& (3)\\ 
BD+61$^{\circ}$154 & $<$0.09 &           &  & &&&& (3) \\ 
T Ori           &$<$0.15  &           &  & & & &&(3)\\ 
V380 Ori        &$<$0.1  &           &  & & &&& (3)\\ 
HD 250550       &$<$0.12  &           &  & &&&& (3) \\ 
Lk H$\alpha$ 208&$<$0.03  &           &  & &&&& (3) \\ 
VV Ser          &$<$0.05  &           &  & &&&& (3) \\ 
WW Vul          &$<$0.09  &           &  & &&&& (3) \\ 
BD+46$^{\circ}$3471&$<$0.1  &           &  & &&&& (3) \\ 
Lk H$\alpha$ 233 &$<$0.04 &           &  & &&&& (3) \\ 
\hline
WL 16 & 0.17(0.03) &  & & & 5(0.4)&& & (4)\\
\hline
\end{tabular}}
\par
\smallskip
{\small Integrated fluxes (after continuum substraction) and uncertainty (in between brackets) are in units of 10$^{-14}$ W/m$^2$.
For non-detections, we give for the 3.3, 6.2 and 11.3~$\mu$m feature 5$\sigma$ limits 
estimated from the spectrum of \cite{meeus2001} and assuming constant feature widths
taken from \cite{li2001a}. We have not included the 11.2(3)~$\mu$m band
for the sources with strong silicate emission. \\
$^a$ From \cite{brooke93}. \\
$^{b}$ In the spectrum of HD~100546 a 11.2(3)~$\mu$m PAH feature is present
but may be blended with the crystalline olivine band at 11.3~$\mu$m \cite[]{malfait98}.\\
$^c$ Measured in ground-based spectrum \cite[]{geballe97}. \\
$^{d}$ \cite{hanner94} report the presence of an 11.2~$\mu$m feature in their UKIRT spectrum.
They attribute this feature to the presence of crystalline silicate but it could also be a PAH band.\\
References: (1) \cite{vankerckhoven2002}; (2) \cite{meeus2001}; (3) \cite{brooke93};
(4) From the spectrum of \cite{tokunaga91} and \cite{hanner92} for the 3.3 and 11.3~$\mu$m feature, respectively.}
\end{table}