J/ApJ/964/37 LCOGT LCs of the variable AGN 6dFGS gJ022550.0-060145 (Li+, 2024)
A reverberation mapping study of a highly variable active galactic nucleus
6dFGS gJ022550.0-060145.
Li D., Sun M., Wang J., Wu J., Zhang Z.
<Astrophys. J., 964, 37 (2024)>
=2024ApJ...964...37L 2024ApJ...964...37L
ADC_Keywords: Active gal. nuclei; Photometry, ugriz
Keywords: Accretion ; Active galactic nuclei ; Supermassive black holes ;
Reverberation mapping
Abstract:
We use LCOGT observations (MJD 59434-59600) with a total exposure time
of ∼50hr and a median cadence of 0.5d to measure the interband time
delays (with respect to u) in the g, r, and i continua of a highly
variable active galactic nucleus (AGN), 6dFGS gJ022550.0-060145. We
also calculate the expected time delays of the X-ray reprocessing of a
static Shakura-Sunyaev disk according to the source's luminosity and
virial black hole mass; the two parameters are measured from the
optical spectrum of our spectroscopic observation via the Lijiang 2.4m
telescope. It is found that the ratio of the measured time delays to
the predicted ones is 2.6-1.3+1.3. With optical light curves
(MJD53650-59880) from our new LCOGT and archival Zwicky Transient
Facility, Pan-STARRS, Catalina Sky Survey, and ATLAS observations, and
Wide-field Infrared Survey Explorer (WISE) data (MJD 55214-59055), we
also measured time delays between WISE W1/W2 and the optical emission.
W1 and W2 have time delays (with respect to V), 9.6-1.6+2.9x102d
and 1.18-0.10+0.13x103d in the rest frame, respectively; hence,
the dusty torus of 6dFGS gJ022550.0-060145 should be compact. The time
delays of the W1 and W2 bands are higher than the dusty torus
size-luminosity relationship of Lyu+ (2019ApJ...886...33L 2019ApJ...886...33L). By
comparing the infrared and optical variability amplitude, we find that
the dust-covering factors of the W1 and W2 emission regions are 0.7
and 0.6, respectively. Future broad emission-line reverberation
mapping of this target and the results of this work enable us to
determine the sizes of the AGN main components simultaneously.
Description:
Our target is 6dFGS gJ022550.0-060145. This source is highly variable
according to the Catalina Sky Survey (CSS; Drake+ 2009ApJ...696..870D 2009ApJ...696..870D)
and Zwicky Transient Facility (ZTF; Masci+ 2019PASP..131a8003M 2019PASP..131a8003M)
observations (Section 2.1).
We use the Las Cumbres Observatory Global Telescope (LCOGT) in four
optical bands (u, g, r, and i) from 2021 August 3 to 2022 January 16
to intensively monitor this source. The median cadence of our LCOGT
observations is 0.5 day. To probe the intrinsic AGN variability, we
require that the S/Ns for our observations are higher than 50 for the
g (∼4700Å), r (∼6215Å), and i (∼7545Å) bands; for the u band
(∼3540Å), the S/N is larger than 40 since its variability amplitude
is expected to be higher than other bands. Hence, for the air mass
≤1.4, the required exposure time durations for the u, g, r, and i
bands are 650, 90, 60, and 60s, respectively. The total LCOGT
exposure time is ∼50hr.
We use the Yunnan Faint Object Spectrograph and Camera (YFOSC) mounted
on the Lijiang 2.4m telescope at the Yunnan Observatories of the
Chinese Academy of Sciences to take a high S/N optical spectrum of our
source on 2022 November 20. See Section 2.2.
Objects:
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RA (ICRS) DE Designation(s)
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02 25 50.04 -06 01 45.1 6dFGS gJ022550.0-060145 = 6dFGS gJ022550.0-060145
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 23 581 Las Cumbres Observatory Global Telescope (LCOGT)
light curves
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See also:
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/788/159 : 17 Seyfert 1 galaxies light curves (Koshida+, 2014)
J/ApJ/825/126 : SEAMBHs. V. The third year (Du+, 2016)
J/ApJ/821/56 : Space telescope RM project. III. NGC5548 (Fausnaugh+, 2016)
J/AJ/152/25 : The UV-bright Quasar Survey (UVQS) DR1 (Monroe+, 2016)
J/ApJ/856/6 : SEAMBHs IX. 10 new Hβ light curves (Du+, 2018)
J/ApJ/880/126 : SDSS RM project: continuum lags (Homayouni+, 2019)
J/ApJ/887/135 : V-band, 5100Å and broad emission LCs of Mrk 79 (Lu+, 2019)
J/ApJ/886/33 : MIR RM analysis of 87 z<0.5 PG AGNs (Lyu+, 2019)
J/other/Sci/373.789 : optical variability of AGNs (Burke+, 2021)
J/ApJ/940/20 : z<0.8 AGNs from MQC with robust lags from ZTF (Guo+, 2022)
J/ApJ/958/195 : AGN STORM 2. IV. Swift XRT & UVOT monitoring (Cackett+, 2023)
J/A+A/672/A132 : MCG 08-11-011 narrowband light curves (Fian+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 1 A1 --- Filt [ugri] LCOGT Filter
3- 12 F10.4 d MJD [59434/59599.44] Modified Julian Date
(JD-2400000.5)
14- 18 F5.2 mag omag [17.04/17.52] Observed AB magnitude in Filter
20- 23 F4.2 mag e_omag [0.01/0.05] Uncertainty in omag
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-May-2026