\documentclass[tikz,border=0.1in]{standalone}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage{amssymb, amsmath, amsthm}

\usepackage{pgfplots}
\usepackage{pgfplotstable}

\begin{document}

\begin{tikzpicture}
\begin{axis} [
  ylabel=$\mathrm{ln}(T)$,
  xlabel=$\mathrm{ln}(d)$,
  xmin=-6.45, xmax=-5.95,
  ymin=1.85, ymax=2.65,
  legend pos = outer north east,
]
  \addplot+ [mark=none,domain=-7:-5] {-1.897*x - 9.4668};
  \addlegendentry {$-1.9x - 9.5$};
  \addplot+ [only marks,mark=*,color=blue,mark options={fill=blue}] table [col sep=comma, x index=2, y index=3] {data/var_d.csv};
\end{axis}
\end{tikzpicture}

\end{document}