Using fit in TGraph

I created a function using TF1 and then subsequently called Fit on a TGraph object. While the parameters are output to stdout, how can I get access to the values internally?

Example:
tfit = new TF1(“mine”,“pol1”,0.0, 1.0);
bg->Fit(tfit,"","",0.48e-3, 1.0e-3);

bg is a TGraph object. I then try to gain access to the fit data parameters
tfit->GetParameter(1), which only give the starting value.

Any clues?

Chris

bg->GetFunction("mine")->GetParameter(1);
Rene