Fejér-type positive operator based on Takenaka-Malmquist system on unit circle

Let φ={φk}k=−∞∞ denote the extended Takenaka–Malmquist system on unit circle T and let σn,φ(f), f∈L1(T), be the Fejér-type operator based on φ, introduced by V. N. Rusak. We give the convergence criteria for σn,φ(f) in Banach space C(T). Also we prove the Voronovskaya-type theorem for σn,φ(f) on class of holomorphic functions representable by Cauchy-type integrals with bounded densities.

Keywords: Holomorphic functions; Takenaka–Malmquist system; Fejér type operator; Blaschke product; Frostman condition