High-resolution X-ray and ultraviolet spectroscopy of the complex intrinsic absorption in NGC 4051 with Chandra and the Hubble Space Telescope

M. J. Collinge, W. N. Brandt, Shai Kaspi, D. Michael Crenshaw, Martin Elvis, Steven B. Kraemer, Christopher S. Reynolds, Rita M. Sambruna, Beverley J. Wills

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Abstract

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 Hubble Space Telescope 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-1 and a low-velocity blue-shifted system at -600 ± 130 km s-1. 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 and 30 km s-1. 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 that 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.

Original languageEnglish (US)
Pages (from-to)2-17
Number of pages16
JournalAstrophysical Journal
Volume557
Issue number1 PART 1
DOIs
StatePublished - Aug 10 2001

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Collinge, M. J., Brandt, W. N., Kaspi, S., Crenshaw, D. M., Elvis, M., Kraemer, S. B., Reynolds, C. S., Sambruna, R. M., & Wills, B. J. (2001). High-resolution X-ray and ultraviolet spectroscopy of the complex intrinsic absorption in NGC 4051 with Chandra and the Hubble Space Telescope. Astrophysical Journal, 557(1 PART 1), 2-17. https://doi.org/10.1086/321635