Thank you Sir for your response, but it's still not working. The graph I am getting is attached:
rm = (( 1 + 2 \[Nu] ) Rg)/2;
bc = Sqrt[rm^2 (1 - Rg/rm)^(1 - 2 \[Nu])];
\!\(\*OverscriptBox[
StyleBox["a",
FontSize->12], \(_\)]\) = Sqrt[(2 rm)/((5 - 2 \[Nu]) Rg)];
\!\(\*OverscriptBox[\(b\), \(_\)]\) =
Sqrt[(2 rm )/(
Rg (5 - 2 \[Nu]) )] (
Log[(16 rm (5 - 2 \[Nu])^2)/((-1 + 2 \[Nu]) Rg) ((4 - 2 \[Nu]) -
Sqrt[(3 - 2 \[Nu]) (5 - 2 \[Nu])])^2]) - \[Pi];
Rg = 2 M;
\[Theta] = bc/\[ScriptCapitalD]LS (1 + E^((
\!\(\*OverscriptBox[\(b\), \(_\)]\) - \[Pi] + \[Beta])/
\!\(\*OverscriptBox[
StyleBox["a",
FontSize->12], \(_\)]\))) (180*3600)/\[Pi]*10^6;
\[Beta]s = Rs/\[ScriptCapitalD]LS;
Rs = 6.96*10^8; \[Beta]0 = 0 \[Beta]s; M =
10 (1476); \[ScriptCapitalD]OS = 1.496*10^11; \[ScriptCapitalD]LS =
3.08567758*10^14 + 1.496*10^11;
\[ScriptCapitalD]OL = 3.08567758*10^14; \[Nu] = 1;
k = Plot[Log[10, \[Theta]], {\[Beta], -10, 10}, PlotRange -> All,
Frame -> True, Axes -> False, PlotStyle -> {Red}]