7 research outputs found
A soft x-ray reverberation lag in the agn ESO 113-G010
Reverberation lags have recently been discovered in a handful of nearby,
variable AGN. Here, we analyze a ~100 ksec archival XMM-Newton observation of
the highly variable AGN, ESO 113-G010 in order to search for lags between hard,
1.5 - 4.5 keV, and soft, 0.3 - 0.9 keV, energy X-ray bands. At the lowest
frequencies available in the lightcurve (<1.5E-4 Hz), we find hard lags where
the power-law dominated hard band lags the soft band (where the reflection
fraction is high). However, at higher frequencies in the range (2-3)E-4 Hz we
find a soft lag of -325 +/- 89 s. The general evolution from hard to soft lags
as the frequency increases is similar to other AGN where soft lags have been
detected. We interpret this soft lag as due to reverberation from the accretion
disk, with the reflection component responding to variability from the X-ray
corona. For a black hole mass of 7E6 M(solar) this corresponds to a
light-crossing time of ~9 R_g/c, however, dilution effects mean that the
intrinsic lag is likely longer than this. Based on recent black hole
mass-scaling for lag properties, the lag amplitude and frequency are more
consistent with a black hole a few times more massive than the best estimates,
though flux-dependent effects could easily add scatter this large
The remarkable X-ray variability of IRAS 13224-3809 - I. The variability process
We present a detailed X-ray timing analysis of the highly variable NLS1
galaxy, IRAS 13224-3809. The source was recently monitored for 1.5 Ms with
XMM-Newton which, combined with 500 ks archival data, makes this the best
studied NLS1 galaxy in X-rays to date. We apply standard time- and
Fourier-domain in order to understand the underlying variability process. The
source flux is not distributed lognormally, as would be expected for accreting
sources. The first non-linear rms-flux relation for any accreting source in any
waveband is found, with . The light
curves exhibit significant strong non-stationarity, in addition to that caused
by the rms-flux relation, and are fractionally more variable at lower source
flux. The power spectrum is estimated down to Hz and consists of
multiple peaked components: a low-frequency break at Hz, with
slope down to low frequencies; an additional component breaking at
Hz. Using the high-frequency break we estimate the black hole
mass , and mass accretion rate
in Eddington units, . The non-stationarity is
manifest in the PSD with the normalisation of the peaked components increasing
with decreasing source flux, as well as the low-frequency peak moving to higher
frequencies. We also detect a narrow coherent feature in the soft band PSD at
mHz, modelled with a Lorentzian the feature has and an
%. We discuss the implication of these results for
accretion of matter onto black holes
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The remarkable X-ray variability of IRAS 13224-3809 - I. The variability process
© Crown copyright 2018. We present a detailed X-ray timing analysis of the highly variable narrow-line Seyfert 1 (NLS1) galaxy IRAS 13224-3809. The source was recently monitored for 1.5 Ms with XMM-Newton, which, combined with 500 ks archival data, makes this the best-studied NLS1 galaxy in X-rays to date. We apply standard time- and Fourier-domain techniques in order to understand the underlying variability process. The source flux is not distributed lognormally, as expected for all types of accreting sources. The first non-linear rms-flux relation for any accreting source in any waveband is found, with rms ∝ flux2/3. The light curves exhibit significant strong non-stationarity, in addition to that caused by the rms-flux relation, and are fractionally more variable at lower source flux. The power spectrum is estimated down to ∼10−7 Hz and consists of multiple peaked components: a low-frequency break at ∼10−5 Hz, with slope α < 1 down to low frequencies, and an additional component breaking at ∼10−3 Hz. Using the high-frequency break, we estimate the black hole mass MBH = [0.5-2] × 106 M☉ and mass accretion rate in Eddington units, m Edd ≳ 1. The broad-band power spectral density (PSD) and accretion rate make IRAS 13224-3809 a likely analogue of very high/intermediate-state black hole X-ray binaries. The non-stationarity is manifest in the PSD with the normalization of the peaked components increasing with decreasing source flux, as well as the low-frequency peak moving to higher frequencies. We also detect a narrow coherent feature in the soft-band PSD at 7 × 10−4 Hz; modelled with a Lorentzian the feature has Q ∼ 8 and an rms ∼3 per cent. We discuss the implication of these results for accretion of matter on to black holes
A dynamic black hole corona in an active galaxy through X-ray reverberation mapping
X-ray reverberation echoes are assumed to be produced in the strongly distorted spacetime around accreting supermassive black holes. This signal allows us to spatially map the geometry of the inner accretion flow1,2—a region that cannot yet be spatially resolved by any telescope—and provides a direct measure of the black hole mass and spin. The reverberation timescale is set by the light travel path between the direct emission from a hot X-ray corona and the reprocessed emission from the inner edge of the accretion disk3,4,5,6. However, there is an inherent degeneracy in the reverberation signal between black hole mass, inner disk radius and height of the illuminating corona above the disk. Here we use a long X-ray observation of the highly variable active galaxy IRAS 13224−3809 to track the reverberation signal as the system evolves on timescales of a day7,8. With the inclusion of all the relativistic effects, modelling reveals that the height of the X-ray corona increases with increasing luminosity, providing a dynamic view of the inner accretion region. This simultaneous modelling allows us to break the inherent degeneracies and obtain an independent timing-based estimate for the mass and spin of the black hole. The uncertainty on black hole mass is comparable to the leading optical reverberation method9, making X-ray reverberation a powerful technique, particularly for sources with low optical variability10
A dynamic black hole corona in an active galaxy through X-ray reverberation mapping
X-ray reverberation echoes are assumed to be produced in the strongly distorted spacetime around accreting supermassive black holes. This signal allows us to spatially map the geometry of the inner accretion flow—a region that cannot yet be spatially resolved by any telescope—and provides a direct measure of the black hole mass and spin. The reverberation timescale is set by the light travel path between the direct emission from a hot X-ray corona and the reprocessed emission from the inner edge of the accretion disk. However, there is an inherent degeneracy in the reverberation signal between black hole mass, inner disk radius and height of the illuminating corona above the disk. Here we use a long X-ray observation of the highly variable active galaxy IRAS 13224−3809 to track the reverberation signal as the system evolves on timescales of a day. With the inclusion of all the relativistic effects, modelling reveals that the height of the X-ray corona increases with increasing luminosity, providing a dynamic view of the inner accretion region. This simultaneous modelling allows us to break the inherent degeneracies and obtain an independent timing-based estimate for the mass and spin of the black hole. The uncertainty on black hole mass is comparable to the leading optical reverberation method, making X-ray reverberation a powerful technique, particularly for sources with low optical variability