You can find the article from Arxiv..

Neutron star (NS) masses and radii can be estimated from observations of photospheric radius-expansion X-ray bursts. By analysing 246 X-ray bursts observed by the Rossi X-ray Timing Explorer from 11 low-mass X-ray binaries, we find a dependence between the persistent spectral properties and the time evolution of the black body normalization during the bursts.

All NS atmosphere models predict that the colour-correction factor decreases in the early cooling phase leading to a characteristic pattern of variability in the measured blackbody normalisation. The model predictions agree with the observations for most bursts occurring in hard, low-luminosity, spectral states, but rarely during soft, high-luminosity states. The observed behaviour may be attributed to the accretion flow, which influences cooling of the NS preferentially during the soft state bursts. This result implies that only the bursts occurring in the hard, low-luminosity spectral states can be reliably used for NS mass and radius determination.