Advective accretion disc-corona model with fallback for tidal disruption events

• Published in: arXiv.org 2022-11
• Main Authors: Mageshwaran, T, Bhattacharyya, Sudip
• Format: Article
• Language: English
• Subjects: Accretion disks; Blackbody; Bolometers; Debris; Deposition; Disruption; Emission; Evolution; Luminosity; Time dependence; X ray sources; X ray spectra; X-ray astronomy
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2211.04632

Tidal disruption events (TDEs) show a correlation between the UV to X-ray spectral index and the Eddington ratio, with non-thermal X-ray emission at the low Eddington ratio. We consider the corona surrounding the accretion disc as a non-thermal X-ray source. We construct a time-dependent and non-relativistic advective accretion disc-corona model for TDEs. The infalling debris is assumed to form a seed disc in time \(t_c\), that evolves due to the mass gain from the infalling debris at the constant outer radius with a mass fallback rate \(\dot{M}_{\rm fb}\) and the mass loss through accretion onto the black hole. The viscous stress in our model depends on gas (\(P_g\)) and total (\(P_t\)) pressures as \(\tau_{r\phi} \propto P_g^{1-\mu} P_t^{\mu}\), where \(\mu\) is a constant. We find that the mass accretion rate \(\dot{M}_a\) evolves from Eddington to sub-Eddington accretion with a late-time evolution close to \(t^{-5/3}\), where \(t\) is the time. We find that the bolometric disc luminosity follows a late-time evolution close to \(t^{-5/3}\). The ratio of total X-ray luminosity from corona to bolometric disc luminosity increases with \(\mu\) and increases at late times for \(\mu \neq 1\). We obtain the X-ray blackbody temperature of the disc that agrees with the temperature from X-ray observations (\(\sim~10^5~{\rm K}\)). We find the radiative efficiency of the disc increases with time and decreases for a disc when the corona is included. We have neglected the outflow, and our model is more applicable for near-to-sub-Eddington accretion and when \(\dot{M}_{\rm fb}\) is sub-Eddington.