Grupe 2006 Swift X射线定X射线吸收元素柱密度

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astro-ph/0612104 [abs, ps, pdf, other] :

Title: Redshift Filtering by Swift Apparent X-ray Column Density
Authors: Dirk Grupe (PSU), John A. Nousek (PSU), Daniel E. vanden Berk (PSU), Peter W.A. Roming (PSU), David N. Burrows (PSU), Neil Gehrels (NASA/GSFC)
Comments: submitted to the Astronomical Journal, 12 pages, 2 figures, 2 tables

We remark on the utility of an observational relation between the absorption column density in excess of the Galactic absorption column density, Delta N_H = N_H,fit - N_H,gal, and redshift, z, determined from all 54 Swift-observed long bursts with spectroscopic redshifts as of 2006 November. The absorption column densities, N_H,fit, are determined from powerlaw fits to the X-ray spectra with the absorption column density left as a free parameter. We find that higher excess absorption column densities are only present in bursts with redshifts z<3.>