Recent highlights from our LCO AGN reverberation mapping key projects.

Flux-flux analysis

Supermassive Black Holes with High Accretion Rates: Mrk 142
Cackett et al., 2020, ApJ, 896, 1  

We performed an intensive accretion disk reverberation mapping campaign on the high accretion rate active galactic nucleus Mrk 142 in early 2019. We measure significant time lags between the different wavelength lightcurves. In the UV and optical, we find that the wavelength-dependent lags, τ(λ), generally follow the relation τ(λ) ∝ λ4/3, as expected for the T ∝ R-3/4 profile of a steady-state, optically thick, geometrically thin accretion disk. The flux-flux analysis (shown in the figure) allowed us to separate the constant and variable components of the spectral energy distribution, finding that the flux dependence of the variable component is consistent with the fν ∝ ν1/3 spectrum expected for a geometrically thin accretion disk. The magnitude of the UV/optical lags is consistent with a highly super-Eddington accretion rate.


Robotic reverberation mapping of the broad-line radio galaxy 3C 120
Hlabathe et al. 2020, MNRAS, in press  

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 (ICCF) to perform multiple-line lag measurements in 3C 120. We find the Hγ, He II λ4686, Hβ and He I λ5876 lags. Using the measured lag and rms velocity width of the Hβ emission line, we determine the mass of the black hole for 3C 120 to be M = 6.3+0.5−0.3× 107( 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 Hβ line, 25 days at line centre decreasing to 17 days in the line wings at ±4000 km s−1.

Fairall 9

Two wavelength dependent signals in Fairall 9
Hernández Santisteban et al. 2020, MNRAS, in press  

We present results of time-series analysis of the first year of the Fairall 9 intensive disc-reverberation campaign. We used Swift and the Las Cumbres Observatory global telescope network to continuously monitor Fairall 9 from X-rays to near-infrared at a daily to sub-daily cadence. The cross-correlation function between bands provides evidence for a lag spectrum consistent with the τ ∝ λ4/3 scaling expected for an optically thick, geometrically thin blackbody accretion disc. Decomposing the flux into constant and variable components, the variable component’s spectral energy distribution is slightly steeper than the standard accretion disc prediction. We find evidence at the Balmer edge in both the lag and flux spectra for an additional bound-free continuum contribution that may arise from reprocessing in the broad-line region. The inferred driving light curve suggests two distinct components, a rapidly variable (< 4 days) component arising from X-ray reprocessing, and a more slowly varying (> 100 days) component with an opposite lag to the reverberation signal.


AGNSTRORM2: Mapping Gas Flows in AGNs by Reverberation in Mrk 817
Peterson et al. 2020, HST GO program, cycle 28  

We propose to determine the location and kinematics of the high-ionization gas in the active galactic nucleus of Mrk 817 via broad emission-line reverberation mapping. Understanding the geometry and kinematics of the broad emission-line region is crucial (a) for identifying where disk winds are launched, (b) for identifying the driving mechanism, and (c) for understanding the radiative and kinetic outflows from nuclei that will allow us to assess the possible impact of AGN feedback on the host galaxy. Moreover, since the masses of the highestredshift quasars are estimated based on scaling relationships involving the C IV 1549 emission line, the kinematics of the C IV line-emitting region must be known to assess the accuracy of such determinations. We propose to obtain 180 COS spectra of Mrk 817, one orbit approximately every other day for a year. This program is modeled after a similar highly successful and high impact monitoring program on NGC 5548 with COS in Cycle 21. The primary science goal is to determine the geometry and kinematics of the C IV and Ly alpha emitting regions. Mrk 817 is a higher luminosity and higher Eddington ratio source than NGC 5548 and therefore likely to have a strong disk wind, although our line of sight to the nucleus is unabsorbed. The NGC 5548 program showed that X-ray data are of critical importance in understanding the ionizing spectrum so accompanying low-cadence Chandra monitoring is also requested. LCO will provide photometric and spectroscopic follow-up (see a test spectrum from the Floyds spectrograph in Hawaii) to complement the HST campaign.