New asymptotic expansions are derived of the Kummer functions M(a, b, z) and U(a, b+1, z) for large positive values of a and b, with z fixed. For both functions we consider b/a <= 1 and b/a >= 1, with special attention for the case a ~ b. We use a uniform method to handle all cases of these parameters.

, ,
Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands

Temme, N.M. (2021). Asymptotic expansions of Kummer hypergeometric functions for large values of the parameters.