  We analyze the low frequency absorption cross section of minimally coupled
massless scalar fields by different kinds of charged static black holes in
string theory, namely the D1-D5 system in d=5 and a four dimensional dyonic
four-charged black hole. In each case we show that this cross section always
has the form of some parameter of the solution divided by the black hole
Hawking temperature. We also verify in each case that, despite its explicit
temperature dependence, such quotient is finite in the extremal limit, giving a
well defined cross section. We show that this precise explicit temperature
dependence also arises in the same cross section for black holes with string
alpha' corrections: it is actually induced by them.
