2004/03/31 by M. A. Worsley, A. C. Fabian, A. Celotti +1 · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Earth Systems and Cosmic Evolution #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2004.07887.x
published as Mon.Not.Roy.Astron.Soc.350:L67-L71,2004 · 5 pages, 5 figures, MNRAS accepted. Minor changes to sections 3.1 and 5
arxiv created 2004/04/15 · openalex publication_date 2004/05/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We report the results of XMM–Newton observations of the X-ray bright, radio-loud blazar GB B1428+4217 at a redshift of z = 4.72. We confirm the presence of soft X-ray spectral flattening at energies ≲0.7 keV as reported in previous ROSAT and BeppoSAX observations. At hard X-ray energies, the spectrum is consistent with a power law, although we find that the spectral slope varied between both XMM–Newton observations and it is also significantly different from that reported previously. Whilst we cannot rule out intrinsic cold absorption to explain the spectral depression, we favour a dust-free warm absorber. Cold absorption requires a column density ∼1.4–1.6 × 1022 cm −2, whilst a warm absorber could have up to ∼1023 cm −2 and an ionization parameter ∼102. The spectrum of GB B1428+4217 shows remarkable parallels with that of the z = 4.4 blazar PMN J0525–3343, in which the available evidence is also most consistent with a warm absorber model.