1999ApJ...516L..57I

The prompt X-ray emission from gamma-ray burst (GRB) 980519, as measured with the Wide Field Cameras on board BeppoSAX, is characterized by a strong soft-to-hard-to-soft evolution. An analysis of the evolution of the X-ray spectrum in terms of a single power-law model shows that the photon index evolved from -2.0 to -1.1 to -2.4. The onset of the burst has such a soft spectrum that the 2-27 keV emission appears to precede the ≳107 keV emission of GRB 980519 (as measured with the Burst and Transient Source Experiment) by about 70 s. Nevertheless, we show that this early spectral variation is part of a smooth evolution over the whole burst and that there is no convincing evidence that the early X-rays originate from a physical process that is different from that giving rise to the remainder of the burst.