Testing super-eddington accretion on to a supermassive black hole: reverberation mapping of PG 1119+120

DOI: 
10.1093/mnras/stad1409
Publication date: 
13/07/2023
Main author: 
Donnan, Fergus R.
IAA authors: 
Aceituno, Jesús
Authors: 
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
Journal: 
Monthly Notices of the Royal Astronomical Society
Publication type: 
Article
Volume: 
523
Pages: 
545
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<SUB>•</SUB>/M<SUB>⊙</SUB>) = 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 ∝ λ<SUP>4/3</SUP>, as expected for a temperature structure of T(R) ∝ R<SUP>-3/4</SUP> for a thin accretion disc, or τ ∝ λ<SUP>2</SUP> 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 λ<SUB>Edd</SUB> &gt; 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.
Database: 
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2023MNRAS.523..545D/abstract
ADS Bibcode: 
2023MNRAS.523..545D
Keywords: 
accretion;accretion discs;galaxies: active;galaxies: individual: PG 1119+120;Astrophysics - Astrophysics of Galaxies;Astrophysics - High Energy Astrophysical Phenomena