ROSAT PSPC detection of soft X-ray absorption in GB 1428+4217: The most distant matter yet probed with X-ray spectroscopy

Preprint

5 May 2000

preprint
Published by arXiv in arXiv

https://doi.org/10.48550/arXiv.astro-ph/0005097

Abstract

We report on a ROSAT PSPC observation of the highly-luminous z = 4.72 radio-loud quasar GB 1428+4217 obtained between 1998 December 11 and 17, the final days of the ROSAT satellite. The low-energy sensitivity of the PSPC detector was employed to constrain the intrinsic X-ray absorption of the currently most distant X-ray detected object. Here we present the detection of significant soft X-ray absorption towards GB 1428+4217, making the absorbing material the most distant matter yet probed with X-ray spectroscopy. X-ray variability by 25+-8 per cent is detected on a timescale of 6500 s in the rest frame. The X-ray variation requires an unusually high radiative efficiency of at least 4.2, further supporting the blazar nature of the source.

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Version 1, 2000-05-05, ArXiv
Published version: Monthly Notices of the Royal Astronomical Society, 315 (2), L23.

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