An X-ray burst with strong photospheric radius expansion observed from thesource 4U1724-307 in Terzan 2

We present results of the RXTE observations of an extremely intense X-ray b urst detected from the source 4U 1724-307 in the globular cluster Terzan 2. The burst profile was complex consisting of two precursors and a long prim ary peak. During the first (strong) precursor the source luminosity, L simi lar to 3.6 x 10(38) erg s(-1),was comparable with that measured in the main event. The structure of the profile, its dependence on energy and observed spectral evolution indicated strong photospheric expansion of a neutron st ar. The effective temperature and radius of the photosphere were estimated from the black body model at different stages of expansion, their correlati ons and specific features of the profile were analyzed and discussed.