\begin{table}%t1
 \caption{Values of different parameters used in Crifo \& Rodionov (1997)
equations. $T_{\rm g}$ is taken from Rodionov et~al. (2002); $\rho_{\rm d}$ from
Olsson-Steel (1987).}
\label{tab:para}
%\centering
\par
\begin{tabular}{ccc}
\hline \hline
Symbol & Name & Value \\
\hline
$\gamma$ & ratio of specific (water) heats & $\frac{4}{3}$      \\
$T_{\rm g}$   & temperature of gas    & $[100;175]$ K         \\
$m$     & mass of gas molecule  &  $18$ amu  \\
$A$     & geometric albedo of nucleus     &  $0.04$       \\
$c_{\odot}$     & solar constant        &  $1353~{\rm W~m}^{-2}$   \\
$\rho_{\rm d}$        & dust density    &  $2000~{\rm kg~m}^{-3}$  \\
$\alpha_{\rm s}$      & coefficient of sublimation    &  $1$  \\
$L_{\rm s}$   & latent heat of sublimation    &  $2833 \: 10^3 \: {\rm J~kg}^{-1}$ \\
$r_{\rm h}$   & heliocentric distance &  $q \le r_{\rm h} \le 3.0$~au  \\
$z$     & angle to subsolar point       &  $-90^\circ  \le z \le 90^\circ $     \\
$\epsilon$      & emissivity    &  $0.9$        \\
$T_{\rm i}$   & temperature of pure ice       &  $\simeq$$180$~K     \\
$a_\star$       & critical radius & a~few~$\mu$m \\
\hline
\end{tabular}
\end{table}