NGC 4388: A test case for relativistic disk reflection and fe k fluorescence features
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Author/Creator ORCID
Date
2023-03-16
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Citation of Original Publication
Tahir Yaqoob, P Tzanavaris, S LaMassa, NGC 4388: A test case for relativistic disk reflection and fe k fluorescence features, Monthly Notices of the Royal Astronomical Society, 2023;, stad782, https://doi.org/10.1093/mnras/stad782
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This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Tahir Yaqoob, P Tzanavaris, S LaMassa, NGC 4388: A test case for relativistic disk reflection and fe k fluorescence features, Monthly Notices of the Royal Astronomical Society, 2023;, stad782, https://doi.org/10.1093/mnras/stad782 is available online at: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad782/7079156
Subjects
Abstract
We present a new analysis of the Suzaku X-ray spectrum of the Compton-thin Seyfert 2 galaxy NGC 4388. The spectrum above ∼2 keV can be described by a remarkably simple and rather mundane model, consisting of a uniform, neutral spherical distribution of matter, with a radial column density of 2.58±0.02×10²³ cm⁻²
, and an Fe abundance of 1.102-₀.₀₂₁⁺⁰.⁰²⁴
relative to solar. The model does not require any phenomenological adjustments to self-consistently account for the low-energy extinction, the Fe Kα and Fe Kβ fluorescent emission lines, the Fe K edge, and the Compton-scattered continuum from the obscuring material. The spherical geometry is not a unique description, however, and the self-consistent, solar abundance MYTORUS model, applied with toroidal and non-toroidal geometries, gives equally good descriptions of the data. In all cases, the key features of the spectrum are so tightly locked together that for a wide range of parameters, a relativistic disk-reflection component contributes no more than ∼2 per cent
to the net spectrum in the 2–20 keV band. We show that the commonly invoked explanations for weak X-ray reflection features, namely a truncated and/or very highly ionized disk, do not work for NGC 4388. If relativistically-broadened Fe Kα lines and reflection are ubiquitous in Seyfert 1 galaxies, they should also be ubiquitous in Compton-thin Seyfert 2 galaxies. The case of NGC 4388 shows the need for similar studies of more Compton-thin AGN to ascertain whether this is true.