Effective absorbing column density in the gamma-ray burst afterglow X-ray spectra

Abstract

We investigate the scaling relation between the observed amount of absorption in the X-ray spectra of Gamma Ray Burst (GRB) afterglows and the absorber redshift. Through dedicated numerical simulations of an ideal instrument, we establish that this dependence has a power law shape with index 2.4. However, for real instruments, this value depends on their low energy cut-off, spectral resolution and on the detector spectral response in general. We thus provide appropriate scaling laws for specific instruments. Finally, we discuss the possibility to measure the absorber redshift from X-ray data alone. We find that 10^5-10^6 counts in the 0.3-10 keV band are needed to constrain the redshift with 10% accuracy. As a test case we discuss the XMM-Newton observation of GRB 090618 at z=0.54. We are able to recover the correct redshift of this burst with the expected accuracy.

arXiv commentMNRAS accepted. 6 figures. 3 tables

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Cited by in corpus (8)

• Missing cosmic metals revealed by X-ray absorption towards distant sources
• A detailed study of the optical attenuation of gamma-ray bursts in the Swift era
• X-ray absorption towards high-redshift sources: probing the intergalactic medium with blazars
• The dependence of gamma-ray burst X-ray column densities on the model for Galactic hydrogen
• Using realistic host galaxy metallicities to improve the GRB X-ray equivalent total hydrogen column density and constrain the intergalactic medium density
• Investigating time variability of X-ray absorption in Swift GRBs
• X-ray absorbing column densities of a complete sample of short Gamma Ray Bursts
• Constraining X-ray emission in HBL blazars using multiwavelength observations