Low-energy X-ray spectral variability of NGC 4051

McHardy, I. M.; Green, A. R.; Done, Chris; Puchnarewicz, E. M.; Mason, K. O.; Branduardi‐Raymont, G.; Jones, Mark

doi:10.1093/mnras/273.3.549

Cited by 33 publications

(33 citation statements)

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“…The rapid and large-amplitude variability as seen in other NLS1s (Boller 2000) is not detected during our observation. For example, for the NLS1 NGC 4051, McHardy et al (1995) reported a flux variation by a factor of about 10 during a 28 ks ROSAT observation. However, as can be seen in the middle right panel of Fig.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Cardaci

Santos-Lleó

Krongold

et al. 2009

A&A

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Aims. The detailed analysis of all data taken by the XMM-Newton satellite of UGC 11763 to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus. Methods. The continuum emission was studied through the EPIC spectra taking profit of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of this source. Results. A power law with a photon index Γ = 1.72−0.01 accounts for the continuum emission of this source in the hard X-rays from 10 down to 1 keV. At lower energies, a black body model with kT = 0.100 ± 0.003 keV provides a good description of the observed soft excess. The absorption signatures in the spectra of UGC 11763 are consistent with the presence of a two phase ionized material (log U = 1.65 +0.07 −0.08 ; 2.6 ± 0.1 and log N H = 21.2 ± 0.2; 21.51 ± 0.01 cm −2 , respectively) in the line of sight. The physical conditions found are consistent with the two phases being in pressure equilibrium. The low ionization component is more ionized than typically found for warm absorbers in other Seyfert 1 galaxies. There are also signatures of some emission lines: Ovii Heα(r), Ovii Heα(f), a blend of the Neix Heα triplet and Fexviii at λ 17.5 Å.

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Section: Discussionmentioning

confidence: 99%

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Cardaci

Santos-Lleó

Krongold

et al. 2009

A&A

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“…Further observations, probably with Chandra, are required to investigate the putative À2340 km s À1 absorption system further. McHardy et al (1995) and Nicastro et al (1999) modeled ROSAT observations of NGC 4051 and claimed significant ionized X-ray absorption variability. Our observations, in contrast, fail to find any significant FUV absorption variability (though the limited temporal sampling might have caused a coincidence of observing on times when conditions were similar).…”

Section: Ultraviolet-x-ray Connectionmentioning

confidence: 98%

Far Ultraviolet Spectroscopic ExplorerSpectroscopy of Absorption and Emission Lines from the Narrow-Line Seyfert 1 Galaxy NGC 4051

Kaspi¹,

Brandt²,

Collinge³

et al. 2004

Astron J

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We present three Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the narrow-line Seyfert 1 galaxy NGC 4051. The most prominent features in the far-ultraviolet (FUV) spectrum are the O vi emission and absorption lines and the H i Lyman series absorption lines, which are detected up to the Lyman edge. We also identify weak emission from N iii, C iii, and He ii. The C iii line shows absorption, while none is detected in the N iii and He ii lines. In H i and C iii we detect two main absorption systems at outflow velocities of À50 AE 30 and À240 AE 40 km s À1 , as well as a possible third one at about À450 km s À1 . These systems are consistent in velocity with the 10 absorption systems found previously in C iv, N v, and Si iv, though the individual systems are blended together in the FUV spectrum. We estimate column densities of the two main absorption systems and find that the H i column density is lower for systems with larger outflow velocity. We detect no flux or spectral variations of NGC 4051 at FUV wavelengths during three epochs spanning 1 yr. This is consistent with the optical light curve, which shows no variations between the three epochs. It is also consistent with the X-ray light curve, which shows consistent flux levels at the three epochs of the FUSE observations, although the X-ray light curve shows strong variations on much shorter timescales.

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“…PCA response matrices were calculated individually for each observation using PCARSP V2.37, taking into account temporal variations of the detector gain and the changing number of detectors used. Fluxes in the 2-10 keV band were then determined using XSPEC, fitting a simple powerlaw with variable slope but with absorption fixed at the Galactic level of 1.3×10 20 cm −2 (Elvis, Lockman and Wilkes 1988;Stark et al 1992;M c Hardy et al 1995). The errors in the flux are scaled directly from the observed errors in the measured count rate.…”

Section: Rxtementioning

confidence: 99%

Combined long and short timescale X-ray variability of NGC 4051 with RXTE and XMM-Newton

McHardy¹,

Papadakis²,

Uttley³

et al. 2004

Nuclear Physics B - Proceedings Supplements

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We present a comprehensive examination of the X-ray variability of the narrow line Seyfert 1 (NLS1) galaxy NGC 4051, one of the most variable AGN in the sky. We combine over 6.5 years of frequent monitoring observations by RXTE with a > 100 ks continuous observation by XMM-Newton and so present an overall 2-10 keV powerspectral density (PSD) covering an unprecedent frequency range of over 6.5 decades from < 10 −8 to > 10 −2 Hz. The combined RXTE and XMM-Newton PSD is a very good match to the PSD of the galactic black hole binary system (GBH) Cyg X-1 when in a 'high', rather than 'low', state providing the first definite confirmation of an AGN in a 'high' state. We also find that a bending powerlaw, rather than a sharply broken powerlaw, besides being more physical, is a much better description of the high state PSD of Cyg X-1 and is also a better description of the PSD of NGC 4051.At low frequencies the PSD of NGC 4051 has a slope of -1.1 bending, at a frequency ν B = 8 +4 −3 × 10 −4 Hz, to a slope of α H ∼ −2. Although ν B does not depend on photon energy, α H is steeper at lower energies. If ν B scales with mass, we imply a black hole mass of 3 +2 −1 × 10 5 M ⊙ in NGC 4051, which is consistent with the recently reported reverberation value of 5 +6 −3 × 10 5 M ⊙ . Hence NGC 4051 is emitting at ∼ 30% L Edd . NGC 4051 follows the same rms-flux relationship as GBHs, consistent with higher Fourier frequencies being associated with smaller radii.From the cross-powerspectra and cross-correlation functions between XMMNewton lightcurves in different energy bands, we note that the higher energy photons lag the lower energy ones. We also note that the lag is greater for variations of longer Fourier period and increases with the energy separation of the bands. Variations in different wavebands are very coherent at long Fourier periods but the coherence decreases at shorter periods and as the energy separation between bands increases. This behaviour is again similar to that of GBHs, and of MCG-6-30-15, and suggests a radial distribution of frequencies and photon energies with higher energies and higher frequencies being associated with smaller radii.Combining our observations with observations from the literature we find it is not possible to fit all AGN to the same linear scaling of break timescale with black hole mass. However broad line AGN are consistent with a linear scaling of break timescale with mass from Cyg X-1 in its low state and NLS1 galaxies scale better with Cyg X-1 in its high state. We suggest that the relationship between black hole mass and break timescale is a function of at least one other underlying parameter which may be accretion rate or black hole spin or both.

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Low-energy X-ray spectral variability of NGC 4051

Cited by 33 publications

References 0 publications

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Far Ultraviolet Spectroscopic ExplorerSpectroscopy of Absorption and Emission Lines from the Narrow-Line Seyfert 1 Galaxy NGC 4051

Combined long and short timescale X-ray variability of NGC 4051 with RXTE and XMM-Newton

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