On the multiwavelength variability of Mrk 110: two components acting at different time-scales
ABSTRACT We present the first intensive continuum reverberation mapping study of the high accretion-rate Seyfert galaxy Mrk 110. The source was monitored almost daily for more than 200 d with the Swift X-ray and ultraviolet (UV)/optical telescopes, supported by ground-based observations from Las Cumbres Observatory, the Liverpool Telescope, and the Zowada Observatory, thus extending the wavelength coverage to 9100 Å. Mrk 110 was found to be significantly variable at all wavebands. Analysis of the intraband lags reveals two different behaviours, depending on the time-scale. On time-scales shorter than 10 d the lags, relative to the shortest UV waveband (∼1928 Å), increase with increasing wavelength up to a maximum of ∼2 d lag for the longest waveband (∼9100 Å), consistent with the expectation from disc reverberation. On longer time-scales, however, the g-band lags the Swift BAT hard X-rays by ∼10 d, with the z-band lagging the g-band by a similar amount, which cannot be explained in terms of simple reprocessing from the accretion disc. We interpret this result as an interplay between the emission from the accretion disc and diffuse continuum radiation from the broad-line region.
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Award ID(s):
Publication Date:
NSF-PAR ID:
10229889
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
504
Issue:
3
Page Range or eLocation-ID:
4337 to 4353
ISSN:
0035-8711
3. ABSTRACT We carried out photometric and spectroscopic observations of the well-studied broad-line radio galaxy 3C 120 with the Las Cumbres Observatory (LCO) global robotic telescope network from 2016 December to 2018 April as part of the LCO AGN Key Project on Reverberation Mapping of Accretion Flows. Here, we present both spectroscopic and photometric reverberation mapping results. We used the interpolated cross-correlation function to perform multiple-line lag measurements in 3C 120. We find the H γ, He ii λ4686, H β, and He i λ5876 lags of $\tau _{\text{cen}} = 18.8_{-1.0}^{+1.3}$, $2.7_{-0.8}^{+0.7}$, $21.2_{-1.0}^{+1.6}$, and $16.9_{-1.1}^{+0.9}$ d, respectively, relative to the V-band continuum. Using the measured lag and rms velocity width of the H β emission line, we determine the mass of the black hole for 3C 120 to be $M=(6.3^{+0.5}_{-0.3})\times 10^7\, (f/5.5)$ M⊙. Our black hole mass measurement is consistent with similar previous studies on 3C 120, but with small uncertainties. In addition, velocity-resolved lags in 3C 120 show a symmetric pattern across the H β line, 25 d at line centre decreasing to 17 d in the line wings at ±4000 km s−1. We also investigate the inter-band continuum lags in 3C 120 and find that they are generally consistent with τ ∝ λ4/3 as predicted from a geometrically thin, optically thick accretion disc. From the continuum lags,more »
4. ABSTRACT We have measured the wavelength-dependent lags between the X-ray, ultraviolet, and optical bands in the high-accretion rate ($L/L_{\rm Edd}\approx 40{{\ \rm per\ cent}}$) active galactic nucleus (AGN) Mrk 110 during two intensive monitoring campaigns in February and September 2019. After including the 2017 data published by Vincentelli et al., we divided the observations into three intervals with different X-ray luminosities. The first interval has the lowest X-ray luminosity and did not exhibit the U-band excess positive lag, or the X-ray excess negative lag that is seen in most AGNs. However, these excess lags are seen in the two subsequent intervals of higher X-ray luminosity. Although the data are limited, the excess lags appear to scale with X-ray luminosity. Our modelling shows that lags expected from reprocessing of X-rays by the accretion disc vary hardly at all with increasing luminosity. Therefore, as the U-band excess almost certainly arises from Balmer-continuum emission from the broad-line region (BLR), we attribute these lag changes to changes in the contribution from the BLR. The change is easily explained by the usual increase in the inner radius of the BLR with increasing ionizing luminosity.