GRRMHD Simulations of Tidal Disruption Event Accretion Disks around Supermassive Black Holes: Jet Formation, Spectra, and Detectability

Abstract

We report results from general relativistic radiation MHD (GRRMHD) simulations of a super-Eddington black hole (BH) accretion disk formed as a result of a tidal disruption event (TDE). We consider the fiducial case of a solar mass star on a mildly penetrating orbit disrupted by a supermassive BH of mass 10 6 M , and consider the epoch of peak fall back rate. We post-process the simulation data to compute viewing angle dependent spectra. We perform a parameter study of the dynamics of the accretion disk as a function of BH spin and magnetic flux, and compute model spectra as a function of the viewing angle of the observer. We also consider detection limits based on the model spectra. We find that an accretion disk with a relatively weak magnetic field around the BH (so-called SANE regime of accretion) does not launch a relativistic jet, whether or not the BH is rotating. Such models reasonably reproduce several observational properties of non-jetted TDEs. The same is also true for a non-rotating BH with a strong magnetic field (MAD regime). One of our simulations has a rapidly rotating BH (spin parameter 0.9) as well as a MAD accretion disk. This model launches a powerful relativistic jet, which is powered by the BH spin energy. It reproduces the high energy emission and jet structure of the jetted TDE Swift J1644+57 surprisingly well. Jetted TDEs may thus correspond to the subset of TDE systems that have both a rapidly spinning BH and MAD accretion.

Self-intersection of the fallback stream in tidal disruption events

“…As the CIO's mass outflowing rate drops with time, the X-ray fluxes for veiled TDEs may gradually rise with time, as observed in ASASSN-15oi and -15lh (Margutti et al 2017;Gezari et al 2017;Holoien et al 2018b). Our picture is different from those of Dai et al (2018) and Curd & Narayan (2019) which describe that the X-ray to optical flux ratio is controlled by the observer's viewing angle with respect to rotational axis of the accretion disk (instead of the CIO's outflowing direction).…”

“…The partial sky coverage of the CIO provides a unification of the diverse X-ray properties of optically selected TDEs. When the line of sight to the inner accretion disk is not blocked by the CIO, the observer should see optical emission as well as the EUV or soft X-ray emission from the inner accretion disk or its wind (Strubbe & Quataert 2009;Dai et al 2018;Curd & Narayan 2019). When the line of sight is only blocked by the region of the CIO with modest optical depth, the observer may see blueshifted absorption lines from high ionization species (e.g.…”

Radio emission from the unbound debris of tidal disruption events

“…Ayal et al 2000;Rosswog et al 2009;Hayasaki et al 2016;Sadowski et al 2016;Coughlin & Armitage 2017) or finite volume fixed mesh codes (e.g. Guillochon et al 2009;Cheng & Evans 2013;Mockler et al 2018;Curd & Narayan 2018). Both approaches are appropriate for modelling certain aspects of tidal disruption events, but we argue that in this particular case they are inadequate.…”

Simulating realistic disc formation in tidal disruption events

“…The resulting gas distribution also affects the diffusion of photons produced near the black hole and whose interactions with the surrounding matter determines the spectrum of these events, in particular the expected strengths of the various lines (Roth et al 2016). Furthermore, the outcome of the disc formation process specifies the correct initial conditions to be used in simulations of gas accretion in this newly-formed structure where mat-ter is thought to spiral inwards under the effect of magnetic stresses that can also be accompanied with the formation of relativistic jets (Dai et al 2018;Curd & Narayan 2018).…”