Dear all,

I am wondering about what range should be chosen in Athena? Some

Wei, On Sun, Sep 18, 2011 at 9:10 AM, Wei Li wrote: literature

says from 1 to the end; some says from 0.5 to the end.

What literature says this? Do you mean to imply that someone is saying it should be 0.5 or 1.0, and *not* some other value? In principle, the background should start at k=0, and one should use k-weight=1, as Integral_E=E0^E=infinity chi(E) dE = 0 Integral_k=0^k=infinity chi(k) * k * dk = 0 In practice, that is nearly useless beyond the suggestion that the integral (which is to say, the DC component), *should* be zero. Using kmin between 0 and 1 and k-weight between 0 and 2 usually "work best", especially in the sense of "stable". In my experience, the value of E0 is much more important than kmin, and it is hard to predict whether k-weight = 1 or 2 works better. My advice is to not over-think or spend too much time worrying about background subtraction. --Matt