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 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 ƒv ∼ 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.
Citation
Donnan , F R , Hernandez Santisteban , J V , Horne , K , Hu , C , Du , P , Li , Y-R , Xiao , M , Ho , L C , Aceituno , J , Wang , J-M , Guo , W-J , Yang , S , Jiang , B-W & Yao , Z-H 2023 , ' Testing super-eddington accretion on to a supermassive black hole : reverberation mapping of PG 1119+120 ' , Monthly Notices of the Royal Astronomical Society , vol. 523 , no. 1 , pp. 545-567 . https://doi.org/10.1093/mnras/stad1409
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Description
Funding: KH and JVHS acknowledge support from STFC grant ST/R000824/1. CH acknowledges support from the National Science Foundation of China (12122305). PD acknowledges support from NSFC grant 12022301, 11991051, and 11991054, and from National Key R&D Program of China (grant 2021YFA1600404). LCH was supported by the National Science Foundation of China (grants 11721303, 11991052,12011540375, and 12233001) and the China Manned Space Project (CMS-CSST-2021-A04, CMS-CSST-2021-A06).Collections
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