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2004MNRAS.348..783M - Mon. Not. R. Astron. Soc., 348, 783-801 (2004/March-1)
Combined long and short time-scale X-ray variability of NGC 4051 with RXTE and XMM-Newton.
McHARDY I.M., PAPADAKIS I.E., UTTLEY P., PAGE M.J. and MASON K.O.
Abstract (from CDS):
At low frequencies the PSD of NGC 4051 has a slope of -1.1 bending, at a frequency νB= 8+4–3x 10–4 Hz, to a slope of αH∼-2. Although νBdoes not depend on photon energy, αHis steeper at lower energies. If νBscales with mass, we imply a black-hole mass of 3+2–1x 105 M☉in NGC 4051, which is consistent with the recently reported reverberation value of 5+6–3 x105 M☉. Hence NGC 4051 is emitting at ∼30 per cent LEdd.
NGC 4051 follows the same rms-flux relationship as GBHs, consistent with higher Fourier frequencies being associated with smaller radii.
From the cross-power spectra and cross-correlation functions between XMM-Newton light curves 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 time-scale with black-hole mass. However, broad-line AGN are consistent with a linear scaling of break time-scale with mass from Cygnus X-1 in its low state and NLS1 galaxies scale better with Cygnus X-1 in its high state. We suggest that the relationship between black-hole mass and break time-scale is a function of at least one other underlying parameter which may be accretion rate or black-hole spin or both.
Abstract Copyright: 2004 RAS
Journal keyword(s): black hole physics - galaxies: active - galaxies: individual: NGC 4051 - X-rays: binaries - X-rays: galaxies
Simbad objects: 14
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