Testing super-eddington accretion on to 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 β lags and linewidths from which we estimate a black hole mass of log (M•/M⊙) = 7.0, uncertain by ∼0.4 dex. High cadence ph...

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Veröffentlicht in:Monthly notices of the Royal Astronomical Society 2023-05, Vol.523 (1), p.545-567
Hauptverfasser: Donnan, Fergus R, Hernández Santisteban, Juan V, Horne, Keith, Hu, Chen, Du, Pu, Li, Yan-Rong, Xiao, Ming, Ho, Luis C, Aceituno, Jesús, Wang, Jian-Min, Guo, Wei-Jian, Yang, Sen, Jiang, Bo-Wei, Yao, Zhu-Heng
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Sprache:eng
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Zusammenfassung: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 β lags and linewidths from which we estimate a black hole mass of log (M•/M⊙) = 7.0, uncertain by ∼0.4 dex. High cadence photometric monitoring over 2 yr with the Las Cumbres Observatory provides light curves in seven optical bands suitable for intensive continuum reverberation mapping. We identify variability on two time-scales. Slower variations on a 100-d time-scale exhibit excess flux and increased lag in the u′ 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′-band excess and have flux and delay spectra consistent with either τ ∝ λ4/3, as expected for a temperature structure of T(R) ∝ R−3/4 for a thin accretion disc, or τ ∝ λ2 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 $f_{\nu } \sim \rm {const}$. Modelling the SED predicts an Eddington ratio of λEdd > 1, where the flat spectrum can be reproduced by a slim disc with little dust extinction or a thin disc that 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.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stad1409