Power ^ syntax error

Hello,
what is wrong with this code? it throws a syntax error even if I use power. The error is at line DA =

Sub btnCalc_Click

Dim Temp As Int
Dim DA As Int
Dim T_S As Double
Dim T_act_K As Double

T_S = 273.15-(0.0019812*edtPA.Text -15)

If rdoTF = 1 Then
T_act_K = (273.15+((edtTemp.Text + 40) / 9 * 5) -40) ' using F°
Else
T_act_K = (273.15 + edtTemp.Text) ' using C°
End If

DA = edtPA.Text + (T_S/0.0019812) * (1-(T_S / T_act_K) ^ 0.2349690)

End Sub