function [Mu,Th,Sig]=FitOUAR1(Y,tau)

T=size(Y,1);
dX = Y(2:end)-Y(1:end-1);
Xlag = [ones(T-1,1) Y(1:end-1)];

b1= Xlag\dX;
alfa = b1(1);
phi = 1 + b1(2);
sigma_e = var(dX-Xlag*b1);

Mu = alfa/(1-phi);
Th = - log(phi)/tau;
Sig = sigma_e*2*Th/(1-phi^2);