X-Ray Spectral Variability of the Seyfert Galaxy NGC 4051 Observed with Suzaku

2008/11/05 by Yuichi Terashima, Y. Terashima, L. C. Gallo +23
Physics and Astronomy · #Amplitude #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black-body radiation #Emission spectrum #Equivalent width #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Geometry #Ionization #Line (geometry) #Optics #Physics #Power law #Reflection (computer programming) #Spectral density #Spectral line #Spectral slope #Stellar, planetary, and galactic studies #astro-ph

paper · pdf · doi:10.1093/pasj/61.sp1.s299

19 pages, 18 figures, accepted for publication in PASJ (Suzaku 3rd special issue)

arxiv created 2008/11/05 · openalex publication_date 2009/01/30 · arxiv updated 2016/03/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Abstract We report on results from a Suzaku observation of the narrow-line Seyfert 1 NGC 4051. During our observation, large-amplitude rapid variability was seen, and the averaged 2–10 keV flux was 8.1×10^-12erg s^-1cm^-2 which is several times lower than the historical average. The X-ray spectrum hardens when the source flux becomes lower, confirming the trend of spectral variability known for many Seyfert 1 galaxies. The broad-band averaged spectrum and spectra in high- and low-flux intervals were analyzed. The spectra were first fitted with a model consisting of a power-law component, a reflection continuum originating in cold matter, a blackbody component, two zones of ionized absorber, and several Gaussian emission lines. The amount of reflection is rather large (R∼ 7, where R= 1 corresponds to reflection by an infinite slab), while the equivalent width of the Fe-K line at 6.4 keV is modest (140 eV) for the averaged spectrum. We then modeled the overall spectra by introducing partial covering for the power-law component and reflection continuum independently. The column density for the former is 1×10²³cm^-2, while it is fixed at 1×10²⁴cm^-2 for the latter. By comparing the spectra in different flux states, we could identify the causes of spectral variability.

Citations

• The relationship between X-ray variability amplitude and black hole mass in active galactic nuclei
• High‐Resolution X‐Ray and Ultraviolet Spectroscopy of the Complex Intrinsic Absorption in NGC 4051 withChandraand theHubble Space Telescope
• Fourier-resolved energy spectra of the Narrow-Line Seyfert 1 Mkn 766
• X-ray reflection in the narrow-line Seyfert 1 galaxy 1H 0707-495
• Discovery of the Narrow-Line Seyfert 1 Galaxy Markarian 335 in a Historical Low X-Ray Flux State
• X-Ray Imaging Spectrometer (XIS) on Board Suzaku
• Investigating the nature of narrow-line Seyfert 1 galaxies with high-energy spectral complexity
• On characterizing the variability properties of X-ray light curves from active galaxies