Left: Posterior distributions for both SIXSA and the reference provided by BXA. The SIXSA ones have been obtained after weighted importance sampling, drawing 400,000 samples with the exact likelihood estimates. There is a perfect match between the SIXSA and BXA posteriors, indicating that the technique works also on real data in the Poisson regime. Right: Folded spectrum and the posterior predictions for the total spectrum and the two components. The spectrum corresponds to a short segment of observation taken at the peak of an X-ray burst: Five parameters, including the column density, can be constrained with ~2000 counts.