Dear Mahendra, The background removal in Athena(/Ifeffit) uses a Fourier transform algorithm, and the k-weight in the Athena panel sets the k-weight for that background-subtraction FT, and so sets how much to weight the low- and high-k range of the data during the background subtraction. This k-weight does not need to be the same as you would normally use to display or fit the chi(k) data, and is one of the parameters that can have a big effect on the resulting chi(k) (the main parameter is Rbkg. The values for E0, kmin, kmax, and the spline clamps also have real impacts on the results). I recommend starting with a kweight of 1 or 2 -- one of those will probably be fine. A kweight of 0 is sometimes OK, but is often not so good, and I've never seen a case where kweight>3 was helpful for background removal. Athena gives a great way to play with these background parameters..... Hope that helps, --Matt