X‐Ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies

Markowitz, A.; Edelson, R.; Vaughan, S.; Uttley, P.; George, I. M.; Griffiths, R. E.; Kaspi, S.; Lawrence, Andy; McHardy, I. M.; Nandra, K.; Pounds, K. A.; Reeves, J. N.; Schurch, Nicholas J.; Warwick, R. S.

doi:10.1086/375330

Cited by 276 publications

(474 citation statements)

References 56 publications

Supporting

Mentioning

436

Contrasting

Order By: Relevance

“…These XMM-Newton data are somewhat insensitive to the low-frequency slope -however, we find it to be constrained to α1 = 0.9 +0.3 −0.1 , which is consistent with the value of 1 typically found from long-term monitoring campaigns (e.g. Uttley, McHardy & Papadakis 2002, Markowitz et al 2003, McHardy et al 2006. The high-frequency slope has a best-fitting value of α2 = 3.5 +0.4 −0.3 , consistent with the average value of 3.08 obtained from a sample of 15 Seyfert galaxies by González-Martín & Vaughan (2012).…”

Section: The Power Spectrumsupporting

confidence: 86%

“…'Xray time lags') 1 which are routinely observed to display similar behaviour but with their frequencies and amplitudes roughly scaled inversely with black hole mass (e.g. Lawrence et al 1987;Uttley, McHardy & Papadakis 2002;Markowitz et al 2003;McHardy et al 2004;McHardy et al 2006;Arévalo et al 2008). Additionally, the rms amplitude of X-ray variability is commonly observed to scale linearly with the flux of the source (i.e.…”

Section: Introductionmentioning

confidence: 92%

See 1 more Smart Citation

X-ray timing analysis of the quasar PG 1211+143

Lobban

Vaughan

Pounds

et al. 2016

Mon. Not. R. Astron. Soc.

Self Cite

View full text Add to dashboard Cite

We report on a timing analysis of a new ∼630 ks XMM-Newton observation of the quasar, PG 1211+143. We find a well-defined X-ray power spectrum with a well-detected bend at ∼7 ×10 −5 Hz, consistent with the established t bend -M BH correlation for luminous, accreting black holes. We find the linear rms-flux relation commonly observed in accreting black hole systems and investigate the energy-dependence of the rms. The fractional rms is roughly constant with energy on short timescales (< 1 day; within observations) whereas there is enhanced soft band variability on long timescales (between observations typically spaced by a few days). Additionally, we also report on the optical-UV variability using the OM on-board XMM-Newton and a ∼2-month-long overlapping monitoring programme with Swift. We find that, although there is little UV variability within observations (< 1 day), UV variations of a few per cent exist on time-scales of ∼days-weeks.

show abstract

Section: The Power Spectrumsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 92%

X-ray timing analysis of the quasar PG 1211+143

Lobban

Vaughan

Pounds

et al. 2016

Mon. Not. R. Astron. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…One of our main targets is NGC 4051 and results from the first 1.5 years of observation (M c Hardy et al 1998) indicated that the slope at low frequencies was probably flatter than that at high frequencies but neither the break frequency, or the slopes, were particularly well defined. Edelson and Nandra (1999), Pounds et al (2001) and Markowitz et al (2003) have all now demonstrated PSD flattening in other AGN at low frequencies, using RXTE data.…”

Section: Introductionmentioning

confidence: 87%

“…However in most other AGN only one break has been found and, although the slopes below the break are not that well defined (eg Uttley et al 2002;Markowitz et al 2003), in general they are closer to -1 than to zero. However it is not clear whether these breaks correspond to the high frequency break in low state systems or the single break in high state systems.…”

Section: Introductionmentioning

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

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…White noise uniformly affects power spectra across all frequencies or periods, and it is accounted for by a uniform confidence level. A growing body of examples across a range of astrophysical phenomena, including X-ray binaries (van der Klis, 1995), Seyfert galaxies (Lawrence et al, 1987;Markowitz et al, 2003), gamma-ray bursts (Ukwatta et al, 2009;Cenko et al, 2010), and quasiperiodic pulsations (QPPs) during solar flares (e.g. Inglis, Ireland, and Dominique, 2015) yield power-law-like spectra.…”

Section: Introductionmentioning

confidence: 99%

Above the Noise: The Search for Periodicities in the Inner Heliosphere

2017

View full text Add to dashboard Cite

Remote sensing of coronal and heliospheric periodicities can provide vital insight into the local conditions and dynamics of the solar atmosphere. We seek to trace long (one hour or longer) periodic oscillatory signatures (previously identified above the limb in the corona by, e.g., Telloni et al. in Astrophys. J. 767, 138, 2013) from their origin at the solar surface out into the heliosphere. To do this, we combined on-disk measurements taken by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and concurrent extreme ultra-violet (EUV) and coronagraph data from one of the Solar Terrestrial Relations Observatory (STEREO) spacecraft to study the evolution of two active regions in the vicinity of an equatorial coronal hole over several days in early 2011. Fourier and wavelet analysis of signals were performed. Applying white-noise-based confidence levels to the power spectra associated with detrended intensity time series yields detections of oscillatory signatures with periods from 6 -13 hours in both AIA and STEREO data. As was found by Telloni et al. (2013), these signatures are aligned with local magnetic structures. However, typical spectral power densities all vary substantially as a function of period, indicating spectra dominated by red (rather than white) noise. Contrary to the white-noise-based results, applying global confidence levels based on a generic backgroundnoise model (allowing a combination of white noise, red noise, and transients following Auchère et al. in Astrophys. J. 825, 110, 2016) without detrending the time series uncovers only sporadic, spatially uncorrelated evidence of periodic signatures in either instrument. Automating this method to individual pixels in the STEREO/COR coronagraph field of view is non-trivial. Efforts to identify and implement a more robust automatic background noise model fitting procedure are needed.B J. Threlfall

show abstract

X‐Ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies

Cited by 276 publications

References 56 publications

X-ray timing analysis of the quasar PG 1211+143

X-ray timing analysis of the quasar PG 1211+143

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

Above the Noise: The Search for Periodicities in the Inner Heliosphere

Contact Info

Product

Resources

About