Testing Super-Eddington Accretion onto a Supermassive Black Hole: Reverberation Mapping of PG 1119+120

Abstract

We measure the black hole mass and investigate the accretion flow around the local ($z=0.0502$) quasar PG 1119+120. Spectroscopic monitoring with Calar Alto provides H$\beta$ lags and linewidths from which we estimate a black hole mass of $\log \left(M_{\bullet }/{\mathrm{M}}_{\odot }\right)=7.0$, uncertain by $\sim 0.4$ dex. High cadence photometric monitoring over two years with the Las Cumbres Observatory provides lightcurves in 7 optical bands suitable for intensive continuum reverberation mapping. We identify variability on two timescales. Slower variations on a 100-day timescale exhibit excess flux and increased lag in the $u^{\prime }$ band and are thus attributable to diffuse bound-free continuum emission from the broad line region. Faster variations that we attribute to accretion disc reprocessing lack a $u^{\prime }$-band excess and have flux and delay spectra consistent with either $\tau \propto {\lambda }^{4/3}$, as expected for a temperature structure of $T(R)\propto R^{-3/4}$ for a thin accretion disc, or $\tau \propto {\lambda }^2$ expected for a slim disc. Decomposing the flux into variable (disc) and constant (host galaxy) components, we find the disc SED to be flatter than expected with $f_{\nu }\sim \mathrm{const}$. Modelling the SED predicts an Eddington ratio of ${\lambda }_{\mathrm{Edd}}>1$, where the flat spectrum can be reproduced by a slim disc with little dust extinction or a thin disc which requires more dust extinction. While this accretion is super-Eddington, the geometry is still unclear, however a slim disc is expected due to the high radiation pressure at these accretion rates, and is entirely consistent with our observations.

23 pages, 16 figures, 10 tables. Accepted for publication in MNRAS

References in corpus (18)

• Testing thermal reprocessing in AGN accretion discs
• The black hole mass - stellar velocity dispersion relation of narrow-line Seyfert 1 galaxies
• On the use of C-stat in testing models for X-ray spectra
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H$\beta$ Time Lags and Implications for Super-Eddington Accretion
• The Radius-Luminosity Relationship Depends on Optical Spectra in Active Galactic Nuclei
• Self-shadowing Effects of Slim Accretion Disks in Active Galactic Nuclei: Diverse Appearance of the Broad-line Region
• Intensive disc-reverberation mapping of Fairall 9: 1st year of Swift & LCO monitoring
• Space Telescope and Optical Reverberation Mapping Project VI: reverberating Disk Models for NGC 5548
• Supermassive black holes with high accretion rates in active galactic nuclei. XI. Accretion disk reverberation mapping of Mrk 142
• Modeling the UV/optical continuum time-lags in AGN
• UV/optical disk thermal reverberation in AGN: an in-depth study with an analytic prescription for the time-lag spectra
• Conditions for Optimal Growth of Black Hole Seeds
• On the multi-wavelength variability of Mrk 110: Two components acting at different timescales
• Testing broad line region models with Reverberation Mapping
• An ALMA CO(2-1) Survey of Nearby Palomar-Green Quasars
• Frequency-resolved lags in UV/optical continuum reverberation mapping
• Accretion Disk Size Measurements of Active Galactic Nuclei Monitored by the Zwicky Transient Facility
• Bayesian Analysis of Quasar Lightcurves with a Running Optimal Average: New Time Delay Measurements of COSMOGRAIL Gravitationally Lensed Quasars

Cited by in corpus (5)

• Continuum optical-UV and X-ray variability of AGN: current results and future challenges
• Investigating the nuclear properties of highly accreting active galactic nuclei with XMM-Newton
• X-ray reverberation modelling of the continuum, optical/UV time-lags in quasars
• Accretion disc reverberation mapping of the quasar 3C 273
• Scalable and Robust Multiband Modeling of AGN Light Curves in Rubin-LSST