\begin{table}%t4
\par
\caption{\label{table:model}Type-I X-ray burst-ignition conditions$^{a}$.} 
%\centerline
 {\begin{tabular}{llllllllllll}
\hline \hline 
\noalign{\smallskip}
Model & $\dot m^b$ & $Z_{\rm CNO}$ & $X_0^c$ & $Q_{\rm b}$ & $y_{{\rm
    ign},9}$ & $T_{{\rm ign},8}$ & $\langle X\rangle$ & $X_{\rm b}$ & $Q_{\rm
    nuc}$ & $E_{40}$ & $\Delta t$ \\ 
 & $(\%~\dot m_{\rm Edd})$ &  & & & & & & & & & (days)\\
\hline 
\multicolumn{12}{c}{Pure helium accretion$^{d}$}\\
1 & 2.2 & 0.02 & 0 & 0.5 & 1.8 & 1.4 & 0 & 0 & 1.6 & 3.4 & 6.5\\
2 & 2.2 & 0.02 & 0 & 0.3 & 7.4 & 1.2 & 0 & 0 & 1.6 & 14 & 27\\
3 & 2.2 & 0.02 & 0 & 0.7 & 0.84 & 1.5 & 0 & 0 & 1.6 & 1.6 & 3.1\\
\hline
\multicolumn{12}{c}{Accretion hydrogen-rich material}\\
4 & 2.2 & 0.02 & 0.7 & 0.5 & 0.13 & 2.0 & 0.38 & 0.07 & 3.1 & 0.49 & 0.48\\
5 & 0.69 & 0.02 & 0.7 & 0.5 & 1.6 & 1.4 & 0.01 & 0 & 1.64 & 3.2 & 19\\
6 & 2.2 & 0.001 & 0.7 & 0.1 & 0.67 & 1.7 & 0.62 & 0.54 & 4.1 & 3.3 & 2.5\\
7 & 2.2 & 0.001 & 0.7 & 0.5 & 0.53 & 1.8 & 0.63 & 0.43 & 4.1 & 2.7 & 2.0\\
\hline
\end{tabular}}
\par
\smallskip
$^{a}$ Models 1, 5, and 6 provide a good match to the
  observed burst energy of $3.5\times 10^{40}\ {\rm erg}$. In
  addition, models 1 and 6 have an accretion rate that matches the
  value inferred from the persistent luminosity;
$^{b}$ we define $\dot m_{\rm Edd}=1.8\times 10^5\ {\rm
    g\ cm^{-2}\ s^{-1}}$, the local accretion rate onto a
  $1.4\ M_\odot$, $R=11.2\ {\rm km}$ neutron star, which infers an
  accretion luminosity equal to the empirically-derived Eddington
  luminosity $3.8\times 10^{38}\ {\rm erg\ s^{-1}}$ from
  \citet{kul03};  
$^{c}$ the hydrogen mass fractions are: in the accreted material $X_0$,
  at the base of the layer at ignition $X_{\rm b}$, and the mass-weighted
  mean value in the layer at ignition $\langle X\rangle$;
$^{d}$ note that the ignition conditions for pure helium accretion do
  not depend on the choice of $Z_{\rm CNO}$. 
\end{table}