The dynamics and electromagnetic emission

J. J. Zanazzi (CITA) // June 8, 2020

Abstract: When a star wanders too close to a SuperMassive Black Hole (SMBH), the star tidally disrupts, producing a luminous transient known as a Tidal Disruption Event (TDE). The compact accretion disks thought to form soon after a TDE were predicted to emit thermal radiation which peaked in the soft X-ray, but TDEs detected in the subsequent decades often peaked in the near UV and optical, sometimes emitting substantial amounts of non-thermal hard X-ray emission which displayed Quasi-Periodic Oscillations (QPOs). This talk discusses how relaxing the assumption of a circular disk co-planar with a spinning SMBH’s equatorial plane may give rise to the rich electromagnetic spectra observed from TDEs. In the first part of the talk, I will discuss the dynamics of a highly-eccentric TDE accretion disk, which forms when the stellar debris on highly-elliptical trajectories do not completely circularize. For our eccentric TDE disk model, we find it is possible to generate UV and optical thermal emission consistent with the optically-bright TDEs observed. In the talk’s second portion, I will discuss how a TDE disk tilted to the equatorial plane of a spinning SMBH is warped due to differential Lens-Thirring precession, how different effects drive and damp the disk’s precession, and discuss how this precession may drive QPOs in the hard X-ray emission of a TDE. Allowing a TDE disk to be eccentric and warped may give rise to the surprising diversity of TDE emission, not predicted by the original TDE models.

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