MCG–6-30-15: long time-scale X-ray variability, black hole mass and active galactic nuclei high states

By I. McHardy, K. Gunn, P. Uttley, M. Goad. 2005

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We present a detailed study of the long time-scale X-ray variability of the Seyfert 1 Galaxy MCG-6-30-15, based on eight years of frequent monitoring observations with the Rossi X-ray Timing Explorer. When combined with the published short-time-scale XMM-Newton observations, we derive the power-spectral density (PSD) covering six decades of frequency from ∼10 -8 to ∼10 -2 Hz. As with NGC 4051, another narrow-line Seyfert 1 galaxy (NLS 1), we find that the PSD of MCG-6-30-15 is a close analogue of the PSD of a galactic black hole X-ray binary system (GBH) in a 'high' rather than a 'low' state. As with NGC 4051 and the GBH Cygnus X-1 in its high state, a smoothly bending model is a better fit to the PSD of MCG-6-30-15, giving a derived break frequency of 7.6 +10 -3 x 10 -5 Hz. Assuming linear scaling of the break frequency with black hole mass, we estimate the black hole mass in MCG-6-30-15 to be ∼2.9 +1.8 -1.6 × 10 6 M ○. . Although, in the X-ray band, it is one of the best observed Seyfert galaxies, there has as yet been no accurate determination of the mass of the black hole in MCG-6-30-15. Here we present a mass determination using the velocity dispersion (M BH -σ*) technique and compare it with estimates based on the width of the Ha line. Depending on the calibration relationship assumed for the M BH -σ* relationship, we derive a mass of between 3.6 and 6 x 10 6 M ○. , consistent with the mass derived from the PSD. Using the newly derived mass and break time-scale, and revised reverberation masses for other active galactic nuclei (AGN) from Peterson et al., we update the black hole mass-break-time-scale diagram. The observations are still generally consistent with narrow-line Seyfert 1 galaxies having shorter break time-scales, for a given mass, than broad-line AGN, probably reflecting a higher accretion rate. However, the revised, generally higher, masses (but unchanged break time-scales) are also consistent with perhaps all of the X-ray bright AGN studied so far being high-state objects. This result may simply be a selection effect, based on their selection from high-flux X-ray all-sky catalogues, and their consequent typically high X-ray/radio ratios, which indicate high-state systems.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/37ba886f81e18c36fbad3271300fe1020a18cea2

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Citations in the corpus

THE LICK AGN MONITORING PROJECT: THE MBH–σ* RELATION FOR REVERBERATION-MAPPED ACTIVE GALAXIES (2010, methodology): “McHardy et al. (2005) used a spectrum around the Ca II triplet to measure σ = 93.5± 8.5 km s−1, using a cross-correlation technique.”
Constraining Black Hole Spin via X-Ray Spectroscopy (2006, methodology): “McHardy et al. (2005) have further narrowed this mass range to 3Y6ð Þ ; 106 M using a variety of methods such as theM- relation, line widths from optical spectra, broad- line region (BLR) photoionization arguments, and X-ray variability.”
X-ray variability of 104 active galactic nuclei - XMM-Newton power-spectrum density profiles (2012, methodology): “McHardy et al. (2005) analysed together the RXTE and XMM-Newton data and found a good fit using the bending power law model.”
Investigating a fluctuating-accretion model for the spectral-timing properties of accreting black hole systems (2005, background): “As an example, the PSD of the Seyfert 1 galaxy MCG–6-30-15 can also be fit with a bending power law model obtaining flatter high-frequency slopes for higher energy light curves (Vaughan et al. 2003).”
Radio Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications (2006, background): “In addition, McHardy et al. (2005) found k 0:4 for this object.”
Suzaku Observations of the Hard X-ray Variability of MCG-6-30-15: the Effects of Strong Gravity Around a Kerr Black Hole (2006, background): “As normal for this source (thought to harbour a black hole with a mass of ∼ 3× 106 M⊙, McHardy et al 2005) the light curve exhibits large amplitude and relatively short timescale variability with variations up to factors 2–3 in a few ks.”
Jets in neutron star X-ray binaries: a comparison with black holes (2005, background): “In particular, the relation between the radio luminosity and the ‘break’ frequency (Migliari et al. 2005), atiming feature observed also in AGN (e.g. McHardy et al. 2005), opens the possibility of the existence of a ’new fundamental plane’ for BHs. Taking into account the mass scaling, we can…”
X-ray reverberation around accreting black holes (2014, unknown): “The same approaches are easily applicable to the contiguous light curves obtained from ‘long-look’ observations of AGN by missions such as EXOSAT (e.g. Lawrence et al. 1987) and currently, XMM-Newton (e.g. McHardy et al. 2005).”