J/ApJS/279/3 ZTF LC analysis of Fermi LAT (4LAC-DR3) AGNs (Xiong+, 2025)
A characteristic optical variability timescale in jetted active galactic nuclei:
a large gamma-ray emission sample.
Xiong D., Sun M., Wang J.-X., Fan J., Xue Y., Gu M., Chen L., Chen Y.,
Ding N., Guo F., Mao J., Ren G., Xue R., Yan D., Yang S., Zhang H.,
Bai J.
<Astrophys. J. Suppl. Ser., 279, 3 (2025)>
=2025ApJS..279....3X 2025ApJS..279....3X
ADC_Keywords: Active gal. nuclei; BL Lac objects; QSOs; Galaxies, Seyfert;
Galaxies, radio; Gamma rays; Photometry; Optical; Redshifts
Keywords: Active galactic nuclei ; Blazars ; Galaxy jets ;
Galaxy accretion disks ; Time domain astronomy ; Time series analysis
Abstract:
The variability mechanisms from jetted active galactic nuclei (AGNs)
are still under debate. Here, the damped random walk (DRW) model,
implemented through Gaussian processes (GPs), is used to fit the
Zwicky Transient Facility long-term optical light curves of
1684 gamma-ray emission jetted AGNs. This analysis yields one of the
largest samples with characteristic optical variability timescales for
jetted AGNs. A single DRW model from GPs can fit the optical light
curve of most jetted AGNs well/potentially well, while there are still
some jetted AGNs whose light curve cannot be fitted well by a single
DRW model. After the jet power, proxied by gamma-ray luminosity, is
introduced as a new parameter, new relationships among intrinsic
variability time scales, black hole mass, and jet power are discovered
for efficient accretion AGNs
(τin∝MBH0.29-0.06+0.06Pjet-0.3-0.03+0.03 with
scatter of approximately 0.09 dex) and for inefficient accretion AGNs
(τin∝MBH0.06-0.07+0.07Pjet0.37-0.11+0.11 with
scatter of approximately 0.14 dex), respectively. Our results support
that the optical variability of jetted AGNs with efficient accretion
may originate within the standard accretion disk at UV-emitting radii
similar to nonjetted AGNs, and is directly related to the acceleration
of shock in the jet and then enhanced through the beaming effect in
beamed AGNs. For the jetted AGNs with inefficient accretion, the
intrinsic timescale is consistent with the escape timescale of
electrons.
Description:
Launched on 2008 June 11, the Fermi Large Area Telescope (LAT) is a
high-energy gamma-ray observatory that covers an energy range from
below 20MeV to over 300GeV. For our study, we utilized the fourth
catalog of AGNs detected by Fermi LAT (4LAC-DR3;
Ajello+ 2022, J/ApJS/263/24), focusing on the high-latitude sample
(|b|>10°). The 4LAC-DR3 high-latitude sample includes
3407 gamma-ray emission AGNs: 755 flat-spectrum radio quasars (FSRQs),
1379 BL Lac objects, 1208 blazars of unknown type (BCU), and
65 nonblazar AGNs.
In this work we collected optical light curves for these Fermi
detected jetted AGNs from the Zwicky Transient Facility (ZTF), which
surveyed the northern sky in g, r, and i bands (with an average
cadence of 3 days) using a 47deg2 wide-field imager mounted on a
48-inch Schmidt telescope at Mount Palomar. The long-term optical
light curves were retrieved from the 19th ZTF public data release
(Masci+ 2019PASP..131a8003M 2019PASP..131a8003M), covering observations from 2018 March
through 2023 July.
Reliable light curves were selected based on the criteria detailed in
Section 2. A total of 1684 gamma-ray-emitting AGNs were selected.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 135 1684 Fitting results of the damped random walk (DRW)
model using Gaussian Processes (GPs) for
γ-ray-emitting jetted AGNs
table2.dat 107 104 Sample of jetted AGNs with efficient accretion that
exhibit good model fitting
table3.dat 100 80 Sample of jetted AGNs with inefficient accretion
that exhibit good model fitting
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See also:
IX/67 : Incremental Fermi LAT 4th source cat. (4FGL-DR3) (Fermi-LAT col., 2022)
J/A+AS/132/83 : BVRI photometry of 7 BL Lac objects (Bai+ 1998)
J/A+A/450/39 : BVRI photometry of 8 red blazars (Gu+, 2006)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/726/16 : γ-ray loud blazars (Linford+, 2011)
J/other/Sci/338.1445 : Relativistic jets from black hole syst. (Nemmen+, 2012)
J/A+A/544/A34 : AGN VLBI imaging study at 2 and 8GHz (Pushkarev+, 2012)
J/other/Nat/515.376 : Power of relativistic jets in blazars (Ghisellini+, 2014)
J/ApJ/789/135 : Gamma-ray bright blazars spectrophot. (Williamson+, 2014)
J/MNRAS/450/3568 : Non-Fermi blazar sample (Xiong+, 2015)
J/ApJS/229/21 : VRI monitoring of QSO 3C 273 in 2005-2016 (Xiong+, 2017)
J/ApJ/866/137 : Blazars variability brightness temp. (Liodakis+, 2018)
J/ApJ/881/125 : 2014-2018 observations of PKS 1502+106 (Ding+, 2019)
J/ApJ/892/105 : 4th catalog of Fermi LAT AGNs (4LAC) (Ajello+, 2020)
J/ApJS/247/49 : gri obs. of S5 0716+714 (2017-2019) (Xiong+, 2020)
J/other/Sci/373.789 : optical variability of AGNs (Burke+, 2021)
J/ApJS/253/46 : Optical spectroscopy of Fermi blazars (Paliya+, 2021)
J/ApJS/263/24 : The 4LAC-DR3 catalog (Ajello+, 2022)
J/other/Univ/8.587 : Gamma-ray emitting jetted AGN (Foschini+, 2022)
J/MNRAS/510/1791 : Blazars study with ZTF DR6 and Roma-BZCAT (Negi+, 2022)
http://irsa.ipac.caltech.edu/Missions/ztf.html : ZTF homepage on NASA/IRSA
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [4FGL]
6- 17 A12 --- 4FGL 4FGL position-based name (JHHMM.m+DDMM)
19- 24 F6.3 [d] logtau [-1.5/3.8] Logarithm, variability damping
time scale
26- 31 F6.3 [d] e_logtau [-2.84/-0.04] Lower uncertainty on logtau
33- 37 F5.3 [d] E_logtau [0.047/1.41] Upper uncertainty on logtau
39- 45 F7.4 [mag] logsigma [-5.91/0.16] Logarithm, variability amplitude
47- 52 F6.3 [mag] e_logsigma [-0.14/-0.007] Lower uncertainty on logsigma
54- 58 F5.3 [mag] E_logsigma [0.007/0.21] Upper uncertainty on logsigma
60- 64 F5.3 d Cad [0.1/1.8] Mean cadence
66- 69 I4 d Time [260/1926] Temporal baseline
71- 76 F6.4 --- sig2sn [0.0001/9.3] Level of noise (1)
78- 82 F5.3 --- Pnor [0/9.25] P value of KS test
84- 88 F5.3 --- Cl [0.05/0.4] 95% confidence limit of the white
noise
90- 94 F5.3 --- ACFmax [0.04/0.43] Maximum autocorrelation function
(ACF) value among all time lags of residuals
96- 100 F5.3 --- PLBmin [0/9.12] Minimum P value of LB test
102- 106 A5 --- Class Class of jetted AGNs (2)
108- 135 A28 --- Assoc Name of Associated counterpart in other bands
--------------------------------------------------------------------------------
Note (1): level of noise σ2=σn2+2.
Note (2): Class of jetted AGNs as follows:
bll = BL Lac (807 occurrences)
fsrq = flat-spectrum radio quasar (424 occurrences)
bcu = blazar of uncertain type (413 occurrences)
rdg = radio galaxy (22 occurrences)
nlsy1 = jetted narrow-line Seyfert 1 galaxy (6 occurrences)
css = compact steep spectrum radio source (5 occurrences)
agn = AGN (4 occurrences)
ssrq = steep-spectrum radio quasar (2 occurrences)
sey = Seyfert galaxy (1 occurrence)
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [4FGL]
6- 17 A12 --- 4FGL 4FGL position-based name (JHHMM.m+DDMM)
19- 22 F4.2 --- z [0.06/3] Redshift, 4LAC-DR3 catalog,
Ajello+ 2020, J/ApJ/892/105
24- 28 A5 --- Class Class of jetted AGNs (1)
30- 34 F5.3 [d] logtau [1/2.24] Logarithm, variability damping
time scale
36- 41 F6.3 [d] e_logtau [-0.38/-0.078] Lower uncertainty on logtau
43- 47 F5.3 [d] E_logtau [0.09/0.61] Upper uncertainty on logtau
49- 53 F5.2 [Msun] logMBH [6.8/10.2] Logarithm, black hole mass
55- 58 F4.2 [Msun] e_logMBH [0/0.9] Uncertainty in logMBH
60- 64 F5.2 [10-7W] logLdisk [43.29/47.4] Logarithm, accretion disk
luminosity
66- 69 F4.2 [10-7W] e_logLdisk [0/0.3] Uncertainty in logLdisk
71- 75 F5.2 [10-7W] logLgam [44.2/48.9] Logarithm, observed
γ-ray luminosity
77- 80 F4.2 [10-7W] e_logLgam [0/0.16] Uncertainty in logLgam
82- 85 F4.2 --- PLindex [2/2.9] γ-ray photon power-law index
87- 90 F4.2 --- e_PLindex [0.01/0.2] Uncertainty in PLindex
92- 96 F5.2 --- delta [1.67/49.8] Doppler factor
98- 102 F5.2 --- e_delta [-1.22/-0.59] Lower uncertainty on delta
104- 107 F4.2 --- E_delta [0.59/1.22] Upper uncertainty on delta
--------------------------------------------------------------------------------
Note (1): Class of jetted AGNs as follows:
bll = BL Lac (12 occurrences)
fsrq = flat-spectrum radio quasar (76 occurrences)
bcu = blazar of uncertain type (12 occurrences)
nlsy1 = jetted narrow-line Seyfert 1 galaxy (3 occurrences)
ssrq = steep-spectrum radio quasar (1 occurrence)
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [4FGL]
6- 17 A12 --- 4FGL 4FGL position-based name (JHHMM.m+DDMM)
19- 23 F5.3 --- z [0.02/0.8] Redshift, 4LAC-DR3 catalog,
Ajello+ 2020, J/ApJ/892/105
25- 27 A3 --- Class Class of jetted AGNs (1)
29- 33 F5.3 [d] logtau [1/2.3] Logarithm, variability damping time
scale
35- 40 F6.3 [d] e_logtau [-0.94/-0.069] Lower uncertainty on logtau
42- 46 F5.3 [d] E_logtau [0.079/0.65] Upper uncertainty on logtau
48- 52 F5.2 [Msun] logMBH [7.2/10.1] Logarithm, black hole mass
54- 57 F4.2 [Msun] e_logMBH [0.1/0.71] Uncertainty in logMBH
59- 63 F5.2 [10-7W] logLdisk [42.69/45]? Logarithm, upper limit for
accretion disk luminosity
65- 69 F5.2 [10-7W] logLgam [42.2/46] Logarithm, observed γ-ray
luminosity
71- 74 F4.2 [10-7W] e_logLgam [0.01/0.2] Uncertainty in logLgam-obs
76- 79 F4.2 --- PLindex [1.48/2.63] γ-ray photon power-law
index
81- 84 F4.2 --- e_PLindex [0.01/0.3] Uncertainty in PLindex
86- 89 F4.2 --- delta [2.47/5.51]? Doppler factor
91- 95 F5.2 --- e_delta [-1.22/-0.59]? Lower uncertainty on delta
97- 100 F4.2 --- E_delta [0.59/1.22]? Upper uncertainty on delta
--------------------------------------------------------------------------------
Note (1): Class of jetted AGNs as follows:
bll = BL Lac (70 occurrences)
bcu = blazar of uncertain type (8 occurrences)
rdg = radio galaxy (2 occurrences)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Feb-2026