High-Resolution X-ray and Ultraviolet Spectroscopy of the Complex Intrinsic Absorption in NGC 4051 with Chandra and HST

We present the results from simultaneous observations of the Narrow-Line Seyfert 1 galaxy NGC 4051 with the Chandra High Energy Transmission Grating Spectrometer and the HST Space Telescope Imaging Spectrograph. The X-ray grating spectrum reveals absorption and emission lines from hydrogen-like and...

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Bibliographic Details
Published in:arXiv.org 2001-04
Main Authors: Collinge, M J, Brandt, W N, Kaspi, Shai, Crenshaw, D Michael, Martin, Elvis, Kraemer, Steven B, Reynolds, Christopher S, Sambruna, Rita M, Wills, Beverley J
Format: Article
Language:English
Subjects:
Blackbody
Curvature
Energy transmission
Galaxies
Helium
High resolution
Seyfert galaxies
Silicon
Soft x rays
Space telescopes
Spectrum analysis
Ultraviolet radiation
Velocity
X ray absorption
X ray imagery
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Summary:We present the results from simultaneous observations of the Narrow-Line Seyfert 1 galaxy NGC 4051 with the Chandra High Energy Transmission Grating Spectrometer and the HST Space Telescope Imaging Spectrograph. The X-ray grating spectrum reveals absorption and emission lines from hydrogen-like and helium-like ions of O, Ne, Mg and Si. We resolve two distinct X-ray absorption systems: a high-velocity blueshifted system at -2340+/-130 km/s and a low-velocity blueshifted system at -600+/-130 km/s. In the UV spectrum we detect strong absorption, mainly from C IV, N V and Si IV, that is resolved into as many as nine different intrinsic absorption systems with velocities between -650 km/s and 30 km/s. Although the low-velocity X-ray absorption is consistent in velocity with many of the UV absorption systems, the high-velocity X-ray absorption seems to have no UV counterpart. In addition to the absorption and emission lines, we also observe rapid X-ray variability and a state of low X-ray flux during the last ~15 ks of the observation. NGC 4051 has a soft X-ray excess which we fit in both the high and low X-ray flux states. The high-resolution X-ray spectrum directly reveals that the soft excess is not composed of narrow emission lines and that it has significant spectral curvature. A power-law model fails to fit it, while a blackbody produces a nearly acceptable fit. We compare the observed spectral variability with the results of previous studies of NGC 4051.
ISSN:2331-8422
DOI:10.48550/arxiv.0104125