J/MNRAS/544/3260 Variability of active galaxies. I. (Lefkir+, 2025)
The variability of active galaxies:
I. Broad-band noise X-ray power spectra from XMM-Newton and Swift.
Lefkir M., Vaughan S., Goad M., Huppenkothen D., Uttley P.
<Mon. Not. R. Astron. Soc. 544, 3260-3279 (2025)>
=2025MNRAS.544.3260L 2025MNRAS.544.3260L (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; X-ray sources ; Gamma rays ; Spectroscopy ;
Stars, masses
Keywords: accretion, accretion discs - galaxies: active - X-rays: galaxies
Abstract:
Accreting supermassive black holes at the centres of galaxies are the
engine of active galactic nuclei (AGN). X-ray light curves of
unabsorbed AGN show dramatic random variability on timescales ranging
from seconds to years. The power spectrum of the fluctuations is
usually well-modelled with a power law that decays as 1/f at low
frequencies, and which bends to 1/f2-3 at high frequencies. The
timescale associated with the bend correlates well with the mass of
the black hole and may also correlate with bolometric luminosity in
the 'X-ray variability plane'. Because AGN light curves are usually
irregularly sampled, the estimation of AGN power spectra is
challenging. In a previous paper, we introduced a new method to
estimate the parameters of bending power law power spectra from AGN
light curves. We apply this method to a sample of 56 variable and
unabsorbed AGN, observed with XMM-Newton and Swift in the 0.3-1.5keV
band over the past two decades. We obtain estimates of the bends in 50
sources, which is the largest sample of X-ray bends in the soft band.
We also find that the high-frequency power spectrum is often steeper
than 2. We update the X-ray variability plane with new bend timescale
measurements spanning from 7 min to 62 days. We report the detections
of low-frequency bends in the power spectra of five AGN, three of
which are previously unpublished: 1H 1934-063, Mkn 766 and Mkn 279.
Description:
This catalogue provides recalibrated masses from reverberation mapping
and scaling relation for this variability study. It contains all the
metadata of the observations (duration, obsID, mean count-rate) used in
this work. Finally, this catalogue also provides all the medians and
associated uncertainties on the parameters derived from the posterior
distributions.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
rmtab.dat 118 74 *Reverberation mapping measurements used to
re-calibrate the black hole masses (33 souces)
srtab.dat 103 29 Line width and luminosity measurements used to
re-calibrate the black hole masses (22 souces)
masses.dat 51 55 Recalibrated black hole masses using either
reverberation mapping (RM) or scaling relation
(SR), 5100Å luminosity and Hbeta time lag
when available (55 souces)
xmmobs.dat 63 377 Details about the XMM-Newton observations used
in this work (56 souces)
swiftobs.dat 60 56 Details about the Swift light curves used in
this work (56 souces)
sgplpost.dat 163 50 Posterior medians and uncertainties for the
single-bending power-law power spectrum model
(50 sources)
dbplpost.dat 230 46 Posterior medians and uncertainties for the
double-bending power-law power spectrum model
(46 sources)
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Note on rmtab.dat: This table contains time delay measurements between the
Hbeta line and the 5100Å continuum using the interpolated cross-correlation
function (ICCF). It also contains Full Width at Half-Maximum (FWHM) and line
width of the Hbeta line in the mean (or single- epoch) and rms spectrum when
available.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: rmtab.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Object Source name (Object)
18- 22 F5.2 d HbTimelag Time delay between the Hbeta and 5100Å
emission measured from the centroid of
the ICCF (Hbeta_timelag)
24- 27 F4.1 d E_HbTimelag Upper error (68% confidence) on Hbeta
timelag (errhighHbetatimelag)
29- 32 F4.1 d e_HbTimelag Lower error (68% confidence) on Hbeta
timelag (errlowHbetatimelag)
34- 39 F6.2 [10-7W] logL5100 ? Decimal logarithm of the AGN luminosity
at 5100Å in units of erg/s
(log10_L5100)
41- 45 I5 km/s FWHMHbmean ? FWHM of the Hbeta line in the mean
spectrum or in a single-epoch spectrum
(FWHMHbetamean)
47- 49 I3 km/s e_FWHMHbmean ? Error (68% confidence) on FWHMHbetamean
(errFWHMHbeta_mean)
51- 55 I5 km/s FWHMHbrms ? FWHM of the Hbeta line in the rms
spectrum (FWHMHbetarms)
57- 60 I4 km/s e_FWHMHbrms ? Error (68% confidence) on FWHMHbetarms
(errFWHMHbeta_rms)
62- 65 I4 km/s sigmaHbmean ? Line width of the Hbeta line in the mean
spectrum or in a single-epoch spectrum
(sigmaHbetamean)
67- 69 I3 km/s e_sigmaHbmean ? Error (68% confidence) on sigmaHbetamean
(errsigmaHbeta_mean)
71- 74 I4 km/s sigmaHbrms ? Line width of the Hbeta line in the rms
spectrum (sigmaHbetarms)
76- 78 I3 km/s e_sigmaHbrms ? Error (68% confidence) on sigmaHbetarms
(errsigmaHbeta_rms)
80-118 A39 --- Ref Bibcode(s) for the reference(s) of the
values in the table (Reference)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: srtab.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Object Source name (Object)
17- 20 I4 km/s FWHMHb FWHM of the Hbeta line in a single-epoch
spectrum (FWHM_Hbeta)
22- 24 I3 km/s e_FWHMHb ? Error (68% confidence) on FWHM_Hbeta
(errFWHMHbeta)
26- 34 E9.7 10+37W LHb ? Hbeta luminosity in units of 1044erg/s
(Lum_Hbeta)
36- 43 F8.5 10+37W L5100 AGN luminosity at 5100 angstrom in units of
1044erg/s (Lum_5100)
45-103 A59 --- Ref Bibcode(s) for the reference(s) of the values
in the table
--------------------------------------------------------------------------------
Byte-by-byte Description of file: masses.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Object Source name (Object)
18- 24 F7.3 10+6Msun MBH Mean recalibrated black hole mass (MBH)
26- 30 F5.2 10+6Msun e_MBH Error (68% confidence) on the mean
recalibrated black hole mass (errMBH)
32- 35 F4.1 [10-7W] logL5100 Decimal logarithm of the AGN luminosity
at 5100Å (log10_L5100)
37- 42 F6.2 d meantau ? Mean time delay from reverberation mapping
if any (mean_tau)
44- 48 F5.2 d e_meantau ? Error (68% confidence) on the mean time
delay if any (errmeantau)
50- 51 A2 --- Method Method used for the recalibration of the
estimate of the black hole mass, RM stands
for reverberation mapping and SR for
scaling relation (Method)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: xmmobs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Object Source name (Object)
18- 26 I9 --- obsid XMM observation identifier (obsid)
28- 37 A10 "date" Date Start date observation (Date)
39- 44 F6.2 ks Exp Net exposure time (Exposure)
46- 50 F5.2 ct/s MeanCR Mean count-rate (Mean_count-rate)
52- 59 F8.5 --- Fvar ? root-mean square of the amplitude
variability of the light curve (Fvar)
61- 63 I3 --- Npts Number of points in the light curves (Npoints)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: swiftobs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Object Source name (Object)
18- 27 A10 "date" StartDate Start date of the light curve (StartDate)
29- 38 A10 "date" EndDate End date of the light curve (EndDate)
40- 43 I4 ks NetExpTime Net exposure time (Net exposure time)
45- 50 F6.4 ct.s-1 MeanCR Mean count-rate (Mean_count-rate)
52- 55 F4.2 --- Fvar root-mean square of the amplitude
variability of the light curve (Fvar)
57- 60 I4 --- Npts Number of points in the light curves
(Npoints)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: sgplpost.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Object Source name (Object)
18- 21 F4.2 --- alpha1 Median value of the low-frequency slope
(alpha_1)
23- 26 F4.2 --- e_alpha1 Lower error of the low-frequency slope,
computed from the 16th percentile
and median (alpha1errlow)
28- 31 F4.2 --- E_alpha1 Upper error of the low-frequency slope,
computed from the 84th percentile
and median (alpha1errhigh)
33- 38 F6.3 d-1 fb1 Median value of the bend frequency (fb1)
40- 45 F6.3 d-1 e_fb1 Lower error of the bend frequency,
computed from the 16th percentile
and median (fb1_errlow)
47- 52 F6.3 d-1 E_fb1 Upper error of the bend frequency,
computed from the 84th percentile
and median (fb1_errhigh)
54- 59 F6.3 d tb1 Median value of the bend timescale (tb1)
61- 67 F7.4 d e_tb1 Lower error of the bend timescale,
computed from the 16th percentile
and median (tb1_errlow)
69- 75 F7.4 d E_tb1 Upper error of the bend timescale,
computed from the 84th percentile
and median (tb1_errhigh)
77- 79 F3.1 --- alpha2 Median value of the high-frequency slope
(alpha_2)
81- 84 F4.2 --- e_alpha2 Lower error of the high-frequency slope,
computed from the 16th percentile
and median (alpha2errlow)
86- 89 F4.2 --- E_alpha2 Upper error of the high-frequency slope,
computed from the 84th percentile
and median (alpha2errhigh)
91- 95 F5.3 ct2/s2 sigma2 Median value of the variance parameter
(sigma2)
97-101 F5.3 ct2/s2 e_sigma2 Lower error of the variance parameter,
computed from the 16th percentile
and median (sigma2_errlow)
103-107 F5.3 ct2/s2 E_sigma2 Upper error of the variance parameter,
computed from the 84th percentile
and median (sigma2_errhigh)
109-112 F4.2 --- nu Median value of nu the error scaling
parameter (nu)
114-117 F4.2 --- e_nu Lower error of nu the error scaling
parameter, computed from the 16th percentile
and median (nu_errlow)
119-122 F4.2 --- E_nu Upper error of nu the error scaling
parameter, computed from the 84th percentile
and median (nu_errhigh)
124-128 F5.3 ct/s mu Median value of the mean (mu)
130-133 F4.2 ct/s e_mu Lower error of the mean, computed from
the 16th percentile and median (mu_errlow)
135-138 F4.2 ct/s E_mu Upper error of the mean, computed from
the 84th percentile and median (mu_errhigh)
140-143 F4.2 --- gamma Median value of gamma the cross-calibration
factor (gamma)
145-148 F4.2 --- e_gamma Lower error of gamma the cross-calibration
factor, computed from the 16th percentile
and median (gamma_errlow)
150-153 F4.2 --- E_gamma Upper error of gamma the cross-calibration
factor, computed from the 84th percentile
and median (gamma_errhigh)
155-163 F9.3 --- lnZ Natural logarithm of the Bayesian evidence
from nested sampling (lnZ)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: dbplpost.dat
--------------------------------------------------------------------------------
Bytes Format Unit s Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Object Source name (Object)
18- 21 F4.2 --- alpha1 Median value of the low-frequency slope
(alpha_1)
23- 26 F4.2 --- e_alpha1 Lower error of the low-frequency slope,
computed from the 16th percentile and median
(alpha1errlow)
28- 31 F4.2 --- E_alpha1 Upper error of the low-frequency slope,
computed from the 84th percentile and median
(alpha1errhigh)
33- 39 F7.4 d-1 fb1 Median value of the low-frequency bend (fb1)
41- 46 F6.3 d-1 e_fb1 Lower error of the low-frequency bend,
computed from the 16th percentile and median
(fb1_errlow)
48- 53 F6.3 d-1 E_fb1 Upper error of the low-frequency bend,
computed from the 84th percentile and median
(fb1_errhigh)
55- 61 F7.3 d tb1 Median value of the low-frequency bend
timescale (tb1)
63- 70 F8.4 d e_tb1 Lower error of the low-frequency bend
timescale, computed from the 16th percentile
and median (tb1_errlow)
72- 79 F8.3 d E_tb1 Upper error of the low-frequency bend
timescale, computed from the 84th percentile
and median (tb1_errhigh)
81- 83 F3.1 --- alpha2 Median value of the intermediate-frequency
slope (alpha_2)
85- 88 F4.2 --- e_alpha2 Lower error of the intermediate-frequency
slope, computed from the 16th percentile
and median (alpha2errlow)
90- 93 F4.2 --- E_alpha2 Upper error of the intermediate-frequency
slope, computed from the 84th percentile
and median (alpha2errhigh)
95-100 F6.2 d-1 fb2 Median value of the high- frequency bend (fb2)
102-106 F5.1 d-1 e_fb2 Lower error of the high- frequency bend,
computed from the 16th percentile and median
(fb2_errlow)
108-114 F7.1 d-1 E_fb2 Upper error of the high- frequency bend,
computed from the 84th percentile and median
(fb2_errhigh)
116-121 F6.4 d tb2 Median value of the high- frequency bend
timescale (tb2)
123-129 F7.5 d e_tb2 Lower error of the high- frequency bend
timescale, computed from the 16th percentile
and median (tb2_errlow)
131-138 F8.5 d E_tb2 Upper error of the high- frequency bend
timescale, computed from the 84th percentile
and median (tb2_errhigh)
140-142 F3.1 --- alpha3 Median value of the high- frequency slope
(alpha_3)
144-146 F3.1 --- e_alpha3 Lower error of the high- frequency slope,
computed from the 16th percentile and median
(alpha3errlow)
148-150 F3.1 --- E_alpha3 Upper error of the high- frequency slope,
computed from the 84th percentile and median
(alpha3errhigh)
152-156 F5.3 ct2/s2 sigma2 Median value of the variance parameter
(sigma2)
158-161 F4.2 ct2/s2 e_sigma2 Lower error of the variance parameter,
computed from the 16th percentile and median
(sigma2_errlow)
163-166 F4.2 ct2/s2 E_sigma2 Upper error of the variance parameter,
computed from the 84th percentile and median
(sigma2_errhigh)
168-171 F4.2 --- nu Median value of nu the error scaling
parameter (nu)
173-176 F4.2 --- e_nu Lower error of nu the error scaling parameter,
computed from the 16th percentile and median
(nu_errlow)
178-181 F4.2 --- E_nu Upper error of nu the error scaling parameter,
computed from the 84th percentile and median
(nu_errhigh)
183-187 F5.3 ct/s mu Median value of the mean (mu)
189-192 F4.2 ct/s e_mu Lower error of the mean, computed from
the 16th percentile and median (mu_errlow)
194-197 F4.2 ct/s E_mu Upper error of the mean, computed from
the 84th percentile and median (mu_errhigh)
199-202 F4.2 --- gamma Median value of gamma the cross-calibration
factor (gamma)
204-207 F4.2 --- e_gamma Lower error of gamma the cross-calibration
factor, computed from the 16th percentile
and median (gamma_errlow)
209-212 F4.2 --- E_gamma Upper error of gamma the cross-calibration
factor, computed from the 84th percentile
and median (gamma_errhigh)
214-222 F9.3 --- lnZ Natural logarithm of the Bayesian evidence
from nested sampling (lnZ)
224-230 F7.3 --- lnBF Natural logarithm of the Bayes factor (lnBF)
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Acknowledgements:
Mehdy Lefkir, ml556(at)leicester.ac.uk
(End) Patricia Vannier [CDS] 15-Oct-2025