\documentclass[twocolumn]{aastex631}
\usepackage{multirow}
\usepackage[normalem]{ulem}
\usepackage{array}
\useunder{\uline}{\ul}{}
\newcommand{\vdag}{(v)^\dagger}
\newcommand\aastex{AAS\TeX}
\newcommand\latex{La\TeX}
\graphicspath{{./}{images/}}
\begin{document}
\begin{deluxetable*}{cccccCCCCC}
\tablenum{1}
\tablecaption{Observation log for {\it XMM-Newton} data \label{tab1}}
\tablewidth{0pt}
\tablehead{
\colhead{Source} & \colhead{Obs Date} & \colhead{Obs ID} & \colhead{Window} &
\colhead{Pile-up} & \colhead{Exposure} & \colhead{Bin Size} &\multicolumn3C{ \mathrm{$ \mu $(counts/s)} }\\
}
\decimalcolnumbers
\startdata
\enddata
\end{deluxetable*}
\begin{deluxetable*}{cCCCcCCcCCC}
\tablenum{2}
\tablecaption{F Variance of HBL Objects\label{tab2}}
\tablewidth{0pt}
\tablehead{
\colhead{Source} & \colhead{Obs ID} & \multicolumn9C{F$_{var}$} \\
}
\decimalcolnumbers
\startdata
\enddata
\end{deluxetable*}
\begin{deluxetable*}{cCcccccc}
\tablenum{3}
\tablecaption{Parameters of the power law fit in soft, hard and total bands\label{tab3}}
\tablewidth{0pt}
\tablehead{
\colhead{Source} & \colhead{Obs ID} & \multicolumn2c{Soft(0.3$-$2.0 keV)} &\multicolumn2c{Hard(2.0$-$10.0 keV)} & \multicolumn2c{Total(0.3$-$10.0 keV)} \\
}
\decimalcolnumbers
\startdata
\enddata
\end{deluxetable*}
Reference for table1 is\autoref{tab1}
Reference for table2 is\autoref{tab2}
Reference for table3 is\autoref{tab3}\\
Reference for table1 is\ref{tab1}
Reference for table2 is\ref{tab2}
Reference for table3 is\ref{tab3}
\end{document}