Global simulations of tidal disruption event disc formation via stream injection in GRRMHD. Issue 3 (2nd August 2021)

• Record Type: Journal Article
• Authors: Curd, Brandon
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 507:Issue 3(2021)
• Page Start: 3207
• Page End: 3227
• Publication Date: 2021-08-02
• Subjects: accretion, accretion discs -- black hole physics -- MHD -- radiative transfer -- X-rays: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab2172
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We use the general relativistic radiation magnetohydrodynamics code KORAL to simulate the accretion disc formation resulting from the tidal disruption of a solar mass star around a supermassive black hole (BH) of mass 10 6 M⊙ . We simulate the disruption of artificially more bound stars with orbital eccentricity e ≤ 0.99 (compared to the more realistic case of parabolic orbits with e = 1) on close orbits with impact parameter β ≥ 3. We use a novel method of injecting the tidal stream into the domain, and we begin the stream injection at the peak fallback rate in this study. For two simulations, we choose e = 0.99 and inject mass at a rate that is similar to parabolic TDEs. We find that the disc only becomes mildly circularized with eccentricity e ≈ 0.6 within the 3.5 d that we simulate. The rate of circularization is faster for pericenter radii that come closer to the BH. The emitted radiation is mildly super-Eddington with $L_{\rm {bol}}\approx 3{-}5\, L_{\rm {Edd}}$ and the photosphere is highly asymmetric with the photosphere being significantly closer to the inner accretion disc for viewing angles near pericenter. We find that soft X-ray radiation with T rad ≈ 3–5 × 10 5 K may be visible for chance viewing angles. Our simulations suggest that TDEs should be radiatively inefficient with η ≈ 0.009–0.014.