Complex X-ray spectral behaviour of NGC 4051 in the low flux state

Abstract

The Narrow Line Seyfert 1 galaxy NGC 4051 was observed in one of its prolonged low-lux states by XMM-Newton in November 2002. Here we present the results of an analysis of EPIC-pn data obtained during the observation. Within the low state, the source shows complex spectral variability which cannot easily be explained by any simple model. However, by making a `flux-flux' plot which combines the low state data with data obtained during a normal flux state, we demonstrate that the extremely hard spectrum observed above 2 keV results from a continuation of the spectral variability seen in the normal state, which is caused by spectral pivoting of the power-law continuum. The pivoting power-law appears to be attached to a Comptonised thermal component of variable flux (blackbody temperature kT~0.1 keV, consistent with the small black hole mass in NGC 4051) which dominates the soft X-ray band in the low state, and is probably the source of seed photons for Comptonisation. Additional constant thermal and reflection components, together with absorption by ionised gas, seem to be required to complete the picture and explain the complex X-ray spectral variability seen in the low state of NGC 4051.

arXiv commentAccepted for publication in MNRAS. 13 pages, 10 figs. A higher resolution eps version of Fig. 8 is included in the source files

References in corpus (16)

• Radiation mechanisms and geometry of Cygnus X-1 in the soft state
• The flux-dependent amplitude of broadband noise variability in X-ray binaries and active galaxies
• Soft state of Cygnus X-1: stable disk and unstable corona
• Understanding the long-term spectral variability of Cygnus X-1 with BATSE and ASM observations
• The iron line in MCG-6-30-15 from XMM-Newton: evidence for gravitational light-bending?
• How the X-ray spectrum of a Narrow-Line Seyfert 1 galaxy may be reflection dominated
• High-Resolution X-ray and Ultraviolet Spectroscopy of the Complex Intrinsic Absorption in NGC 4051 with Chandra and HST
• The swan song: the disappearance of the nucleus of NGC 4051 and the echo of its past glory
• The nature of X-ray spectral variability in Seyfert Galaxies
• The continuum variability of MCG--6-30-15: A detailed analysis of the long 1999 ASCA observation
• The swansong in context: long-timescale X-ray variability of NGC 4051
• Complex Optical-X-ray Correlations in the Narrow-Line Seyfert 1 Galaxy NGC 4051
• Spectral Variability and iron line emission in the ASCA Observations of the Seyfert 1 Galaxy NGC4051
• X-ray spectral variability of the Seyfert galaxy NGC 4051
• Catching NGC 4051 in the low state with Chandra
• Simultaneous EUV and X-ray variability of NGC 4051

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