Cheng, H;
Yuan, W;
Liu, H-Y;
Breeveld, AA;
Jin, C;
Liu, B;
(2019)
Modelling accretion disc emission with generalized temperature profile and its effect on AGN spectral energy distribution.
Monthly Notices of the Royal Astronomical Society
, 487
(3)
pp. 3884-3903.
10.1093/mnras/stz1532.
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Abstract
The broad-band spectral energy distribution (SED) of active galactic nuclei (AGNs) is investigated for a well-selected sample composed of 23 Seyfert 1 galaxies observed simultaneously in the optical/ultraviolet (UV) and X-ray bands with the Neil Gehrels Swift Observatory. The optical to UV continuum spectra are modelled, for the first time, with emission from an accretion disc with a generalized radial temperature profile, in order to account for the intrinsic spectra which are found to be generally redder than the model prediction of the standard Shakura–Sunyaev disc (SSD, Fν ∝ ν+1/3). The power-law indices of the radial temperature profile (Teff(R) ∝ R−p, R is the radius of the accretion disc) are inferred to be p = 0.5–0.75 (a median of 0.63), deviating from the canonical p = 0.75 for the SSD model as widely adopted in previous studies. A marginal correlation of a flatter radial temperature profile (a smaller p-value) with increasing the Eddington ratio is suggested. Such a model produces generally a lower peak of accretion disc emission and thus a smaller bolometric luminosity in some of the AGN, particularly those with high Eddington ratios, than that based on the SSD model by a factor of several. The broad-band SED, the bolometric correction factors, and their dependence on some of the AGN parameters are revisited. We suggest that such non-standard SSD discs may operate in AGN and are at least partly responsible for the reddened optical/UV spectra as observed. One possible explanation for these flattened temperature profiles is the mass-loss process in form of disc winds/outflows.
| Type: | Article |
|---|---|
| Title: | Modelling accretion disc emission with generalized temperature profile and its effect on AGN spectral energy distribution |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stz1532 |
| Publisher version: | https://doi.org/10.1093/mnras/stz1532 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | accretion, accretion discs, black hole physics, galaxies: active, galaxies: Seyfert |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10077396 |
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