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Gamma--ray bursts (GRBs) are the highest--energy explosions in the universe, emitting short bursts of intense gamma--ray and X--ray radiation. The Swift satellite's rapid response capability allows it to locate bursts instantly with the BAT detector and then start observing the X--ray afterglow within minutes with the XRT instrument. By analyzing the XRT spectra, we can measure not only the afterglow emission itself, but also the absorption effects in the intrinsic environment (progenitor environment, interstellar material). The extra absorption in the X--ray spectra can be used to estimate the intrinsic hydrogen column density ($ {N}_{\mathrm{H},\operatorname{int}} $), which provides information on the amount and ionization state of the matter surrounding the GRB. $ {N}_{\mathrm{H},\operatorname{int}} $ typically appears as an additional absorption component above the Galactic absorption in the spectral fit. Measurements based on Swift/XRT data provide important support for understanding the formation environment of GRBs and the physics of the early afterglow. The analysis of these parameters will also contribute to the identification of progenitors of GRBs (e.g., high--mass stars) and to the study of the interstellar material of high--redshift galaxies.

We analyze the Gamma--Ray Burst (GRB) redshift distribution using various density estimation methods. Several density estimators for one--dimensional point processes were tested for different sample sizes up to 1200 events. Our goal was to identify the ``best'' non--parametric radial density estimator for GRBs, and we found that Poisson noise significantly influences results. We identified Boundary Corrected Kernel Density Estimation as the most suitable method and applied it to a dataset of 542 GRBs with spectroscopic redshifts and reconstructed the GRB density function for different distances/redshifts. The relationship between the observed GRB redshift distribution and the cosmic star formation history is briefly discussed.