\begin{table}%t2
\caption{\label{results}Orbital parameters of Her~X-1 determined from the \textit{RXTE} 
observations during 35~d cycles Nos.~257, 269, 303, 313, 323, 351 and
from \textit{INTEGRAL} observations during cycles 351 and 373$^{1}$.}
%\centerline
{\begin{tabular}{l l l l l l }
\hline\hline\noalign{\smallskip}
35~d cycle No.$^{1}$  & $P_{\rm s}$~[s]  & $T_{\pi/2}$~[MJD (TDB)]  & $P_{\rm orb}$~[d]   & ${\rm d}P_{\rm s}/{\rm d}t~[{\rm s~s}^{-1}]$     & ${\rm d}P_{\rm s}/{\rm d}t/{\rm d}t~[{\rm s}^{-1}]$   \\
  \hline\noalign{\smallskip}
257                & 1.237739612(25)$^{2}$  & 50~290.659199(20)$^{2}$  & 1.700167399         & $-(2.8\pm1.0)~10^{-12}$     & 0.0  \\
269                   & 1.237729884(35)         & 50~703.799869(50)          & 1.700167379          & $-(6.8\pm2.5)~10^{-12}$      & 0.0  \\
303                   & 1.237769831(12)         & 51~895.617167(25)          & 1.700167321          & $+(1.54\pm0.17)~10^{-12}$  & 0.0  \\
313                   & 1.237767113(6)           & 52~242.451312(10)          & 1.700167304          & $-(5.7\pm1.5)~10^{-13}$       & 0.0  \\
323                   & 1.237761690(4)           & 52~599.486440(12)          & 1.700167287          & $+(2.8\pm0.2)~10^{-12}$      & $-(2.9\pm0.08)~10^{-17}$  \\
351                   & 1.237758409(8)           & 53~573.682256(35)          & 1.700167240          & $-(7.0\pm0.8)~10^{-13}$       & 0.0  \\  
373                   & 1.237744750(60)         & 54~345.558195(80)          & 1.700167202          & 0.0                                         & 0.0  \\ 
\hline
\end{tabular}}
\smallskip
\par
$^{1}$ The numbering of 35~d cycles follows \citet{Staubert_etal83}:  
``Pulse profile counting'' is applied, based on pulse profile shapes repeating with an average period of 34.98~d \citep{Staubert_etal09}.
$^{2}$ The uncertainties in parentheses are 1-sigma (68\%) ($\chi^2_{\rm min} + 1.0$) 
and refer to the last digit(s). 
\end{table}