Calibration of X-ray absorption in our Galaxy

Prediction of the soft X-ray absorption along lines of sight through our Galaxy is crucial for understanding the spectra of extragalactic sources, but requires a good estimate of the foreground column density of photoelectric absorbing species. Assuming uniform elemental abundances this reduces to having a good estimate of the total hydrogen column density, N Htot = N H I + 2N H 2 . The atomic component, N H I , is reliably provided using the mapped 21 cm radio emission but estimating the molecular hydrogen column density, N H 2 , expected for any particular direction, is difficult. The X-ray afterglows of Gamma Ray Bursts (GRBs) are ideal sources to probe X-ray absorption in our Galaxy because they are…

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  Science and Technology Facilities Council

  Awards: ST/K001000/1, ST/H001972/1, PP/E002064/1