2004A&A...415..443T

We reanalyze the XMM-Newton data of GRB 011211 showing that the spectral features, interpreted by Reeves et al. (2002Natur.416..512R, 2003A&A...403..463R) as due to thermal emission from a collisionally ionized plasma, can be also reproduced by a reflection model (with ionization parameter ξ∼10²). We discuss the implications of this interpretation, estimating the total mass required in the simplified case of a funnel geometry. We conclude that a moderate clumping of the reprocessing material (corresponding to a filling factor of the order of f∼10^–3) is required. Finally we show that, if this interpretation is correct, a bright quasi-thermal component is expected in the optical-UV band (containing about 90% of the luminosity of the illuminating continuum), whose presence can be used to test the reflection model.