5 research outputs found
Continuum reverberation mapping of MCG 08-11-011
We report the results from a photometric reverberation mapping campaign
carried out with the C18 telescope at the Wise Observatory from 2019 to 2020,
targeting the active galactic nucleus (AGN) MCG 08-11-011. The monitoring was
conducted on a daily basis with specially designed narrow-band filters,
spanning from optical to near-infrared wavelengths ( to {\AA})
and avoiding prominent broad emission lines. We aim to measure inter-band
continuum time lags, determine the size-wavelength relation, and estimate the
host-subtracted AGN luminosity for this system. We used the point-spread
function photometry to extract the continuum light curves and measure the
inter-band time lags using several methods, including the interpolated
cross-correlation function, the z-transformed discrete correlation function, a
von Neumann estimator, JAVELIN (in spectroscopic and photometric mode), MICA,
and a multivariate correlation function. We find wavelength-dependent lags,
, up to 7 days between the multiband light curves of MCG
08-11-011. The observed lags are larger than predictions based on standard
thin-disk theory by a factor of . We discern a significantly steeper
() size-wavelength relation than the expected for a geometrically thin and optically thick accretion
disk, which may result from the contribution of diffuse continuum emission to
the flux. These results are similar to those found by previous continuum
reverberation mapping campaigns.Comment: arXiv admin note: text overlap with arXiv:2111.0738
Time-delay measurement of MgII broad line response for the highly-accreting quasar HE 0413-4031: Implications for the MgII-based radius-luminosity relation
We present the monitoring of the AGN continuum and MgII broad line emission
for the quasar HE 0413-4031 () based on the six-year monitoring by the
South African Large Telescope (SALT). We managed to estimate a time-delay of
days in the rest frame of the source using seven
different methods: interpolated cross-correlation function (ICCF), discrete
correlation function (DCF), -transformed DCF, JAVELIN, two estimators of
data regularity (Von Neumann, Bartels), and method. This time-delay is
below the value expected from the standard radius-luminosity relation. However,
based on the monochromatic luminosity of the source and the SED modelling, we
interpret this departure as the shortening of the time-delay due to the higher
accretion rate of the source, with the inferred Eddington ratio of .
The MgII line luminosity of HE 0413-4031 responds to the continuum variability
as , which is consistent with
the light-travel distance of the location of MgII emission at . Using the data of 10 other quasars, we confirm the
radius-luminosity relation for broad MgII line, which was previously determined
for broad H line for lower-redshift sources. In addition, we detect a
general departure of higher-accreting quasars from this relation in analogy to
H sample. After the accretion-rate correction of the light-travel
distance, the MgII-based radius-luminosity relation has a small scatter of only
dex.Comment: 39 pages (23 pages - Main text, 16 pages - Appendix), 21 figures, 14
tables; accepted for publication in the Astrophysical Journa
Continuum reverberation mapping of the quasar PG 2130+099
Aims. We present the results of an intensive six-month optical continuum reverberation mapping campaign of the Seyfert 1 galaxy PG 2130+099 at redshift z = 0.063. The ground-based photometric monitoring was conducted on a daily basis with the robotic 46 cm telescope of the WISE observatory located in Israel. Specially designed narrowband filters were used to observe the central engine of the active galactic nucleus (AGN), avoiding line contamination from the broad-line region (BLR). We aim to measure inter-band continuum time lags across the optical range and determine the size-wavelength relation for this system.
Methods. We used two methods, the traditional point-spread function photometry and the recently developed proper image subtraction technique, to independently perform the extraction of the continuum light curves. The inter-band time lags are measured with several methods, including the interpolated cross-correlation function, the z-transformed discrete correlation function, a von Neumann estimator, JAVELIN (in spectroscopic mode), and MICA.
Results. PG 2130+099 displays correlated variability across the optical range, and we successfully detect significant time lags of up to ∼3 days between the multiband light curves. We find that the wavelength-dependent lags, τ(λ), generally follow the relation τ(λ)∝λ4/3, as expected for the temperature radial profile T ∝ R−3/4 of an optically thick, geometrically thin accretion disk. Despite that, the derived time lags can also be fitted by τ(λ)∝λ2, implying the possibility of a slim, rather than thin, accretion disk. Using the flux variation gradient method, we determined the AGN’s host-galaxy-subtracted rest frame 5100 Å luminosity at the time of our monitoring campaign with an uncertainty of ∼18% (λL5100 = (2.40 ± 0.42)×1044 erg s−1). While a continuum reprocessing model can fit the data reasonably well, our derived disk sizes are a factor of ∼2 − 6 larger than the theoretical disk sizes predicted from the AGN luminosity estimate of PG 2130+099. This result is in agreement with previous studies of AGN/quasars and suggests that the standard Shakura-Sunyaev disk theory has limitations in describing AGN accretion disks