  In this paper we describe some analytical properties of the R^{1/m} law
proposed by Sersic to categorize the photometric profiles of elliptical
galaxies. In particular, we present the full asymptotic expansion for the
dimensionless scale factor b(m) that is introduced when referring the profile
to the standard effective radius. Surprisingly, our asymptotic analysis turns
out to be useful even for values of m as low as unity, thus providing a unified
analytical tool for observational and theoretical investigations based on the
R^{1/m} law for the entire range of interesting photometric profiles, from
spiral to elliptical galaxies.
